JOSÉ CARLOS VEIGA
INDUSTRIAL
GASKETS
3rd Edition
1
©
José Carlos Veiga, 2004
Desenvolvido no Brasil / Developed in Brazil
ISBN 85-98256-01-3
Cover
Alexandre Sampaio
Publishing
Rodrigo Xavier
Revision
Gary M. Springer
Gráfica
Brasilform Editora e Ind. Gráfica
Drawing of this Edition: 3000 exemplares
Print History
Portuguese Language
1st Edition, 1989 – 3000 books
2nd Edition, 1993 – 3000 books
3rd Edition, 1999 – 1000 books
4th Edition 2003 – 3000 books
English Language
1st Edition, 1994 – 10000 books
2nd Edition, 1999 – 3000 books
3rd Edition, 2003 - 3000 books
Spanish Language
1st Edition, 2003 –2000 books
Library of Congress
Catalog Card Number: 99-75712
Price per Copy US$ 20,00
2
To my wife,
MARIA ODETE
3
AUTHORS’S NOTE
The author wishes to
thank The Teadit Group
for support in publishing
its book.
4
Preface
The idea for this book arose by chance. At the end of a technical discussion
that we were having with a client, one of the participants asked why we couldn’t
organize all of the information and examples that we had just presented into one
complete book. He had never seen such a book in the market and knew it would be
beneficial to him and his co-workers.
Based on this simple request and our acknowledgement that the industry was
void of this type of tool, we then decided to create book that could be used by all
aspects of industry. We would compile and organize all the knowledge that our technical
team had with the information of product applications received from our clients. This
application information was critical in establishing a precise correlation between theory
and practice.
The guiding influence in our business philosophy is Research and
Development. Active participation in product applications along with the continuous
search for technical and scientific innovations puts us in an outstanding position as
it relates to the knowledge of “Best Practices” and the development of the new,
innovative solutions. We are always striving for product life cycle improvement and
recognize that the constant search for excellence is never ending. The search for
excellence is evident in our Development Engineering, our Application Engineering
and in our industry experts’ constant work in the field. Our knowledge and commitment
shows through the ability to interact with both Production and Engineering departments
and our close monitoring of product performance. The goal is not to just satisfy our
clients but to educate. We hold ourselves to standards set by leading edge technology
which is evident in our product and service offering.
We have observed the evolution of the fluid sealing industry in the enviable
position of a Global Premier manufacturer for more than 50 years. This experience
along with being a guiding member of the main global organizations of the sector
(FSA – Fluid Sealing Association, ESA – European Sealing Association, ASTM, PVRC
and many others) has given us the ability to amalgamate the past experience with the
present data and future prospective.
Our purpose with this book is create a directory of information that would be
useful to the experts working in this field and fielding the vast majority of the daily
issues met in the industry.
5
6
INDEX
Chapter 1 – Introduction ..........................................................11
Chapter 2 – Design and the New Gasket Constants ..............13
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Leaks .............................................................................................. 13
Sealing ............................................................................................ 14
Forces in a Flanged Joint ............................................................... 14
ASME Code ................................................................................... 15
Notation .......................................................................................... 20
Bolt Torque Calculation.................................................................. 21
Surface Finish................................................................................. 23
Parallelism of Sealing Surfaces ..................................................... 26
Waviness of the sealing Surfaces .................................................. 27
Styles of Flanges ............................................................................ 27
The New Gasket Constants ........................................................... 30
Gasket Maximum Seating Stress ................................................... 41
Chapter 3 – Materials for Non-Metallic Gaskets .................45
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Material Selection .......................................................................... 45
P x T or Service Factor.................................................................. 46
Sheet Packing................................................................................. 46
Polytetrafluoretylene - PTFE ......................................................... 47
Flexible Graphite - Graflex . ........................................................ 47
Elastomers ...................................................................................... 49
Cellulose Fiber Sheet ..................................................................... 51
Cork ................................................................................................ 51
Fabric and Tapes ............................................................................ 51
Tadpole ........................................................................................... 51
7
11. Ceramic Fiber Blankets. ................................................................ 52
12. Ceramic Fiber Millboard ................................................................ 52
13. Beater Addition .............................................................................. 52
Chapter 4 – Compressed Non-Asbestos Gaskets Sheets ....... 57
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
Teadit Compressed Non-Asbestos Gaskets Sheets ...................... 57
Fibers .............................................................................................. 57
Elastomers ...................................................................................... 58
Wire Mesh ...................................................................................... 58
Finishing ......................................................................................... 58
Sheet Dimensions ........................................................................... 58
Physical Characteristics ................................................................. 59
Design ............................................................................................ 60
Manufacturing Tolerances ............................................................. 62
Large Diameter Gaskets ................................................................ 62
Gasket Thickness ........................................................................... 64
Bolt Load ........................................................................................ 64
Gasket Finish .................................................................................. 64
Finish of the Flange Sealing Surface ............................................. 65
Storage ........................................................................................... 65
Teadit Compressed Non-Asbestos Gasket Sheets ........................ 65
Chapter 5 – PTFE Gaskets ................................................................. 89
1.
2.
3.
4.
5.
6.
Polytetrafluorethylene (PTFE) ...................................................... 89
Styles of PTFE Sheets ................................................................... 89
TELON* - Restructured Filled PTFE Sheet ................................. 91
Expanded PTFE ............................................................................. 97
Sintered PTFE Sheets .................................................................... 101
PTFE Envelope Gaskets ................................................................ 102
Chapter 6 – Materials for Metallic Gaskets .................................... 121
1.
2.
3.
4.
5.
Corrosion ........................................................................................ 121
Carbon Steel ................................................................................... 121
Stainless Steel Aisi 304 .................................................................. 122
Stainless Steel Aisi 304L ................................................................ 122
Stainless Steel Aisi 316 .................................................................. 122
8
6.
7.
8.
9.
10.
11.
12.
13.
14.
Stainless Steel Aisi 316L ................................................................ 122
Stainless Steel Aisi 321 .................................................................. 122
Stainless Steel Aisi 347 .................................................................. 122
Monel .............................................................................................. 123
Nickel 200 ...................................................................................... 123
Copper ............................................................................................ 123
Aluminum ....................................................................................... 123
INCONEL ...................................................................................... 123
TITANIUM .................................................................................... 123
Chapter 7 – Spiral Wound Gaskets ......................................... 133
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Spiral Wound Gaskets .................................................................... 133
Materials ........................................................................................ 134
Gasket Density ............................................................................... 135
Gasket Dimensions ......................................................................... 135
Thickness ....................................................................................... 136
Dimensional and Thickness Limitations ......................................... 137
Manufacturing Tolerances........................................................... 138
Finish of the Flange Sealing Surface ............................................. 138
Gasket Maximum Seating Stress ................................................... 139
Gasket Styles .................................................................................. 139
Style 911 Gaskets .......................................................................... 139
Style 913 Gaskets Per Asme B16.20 (Api 601) ............................ 141
Other Standards ............................................................................. 145
Style 913 Gasket Design ................................................................ 145
Style 914 ........................................................................................ 146
Chapter 8 – Jacketed Gaskets ..................................................163
1.
2.
3.
4.
5.
6.
7.
Description ..................................................................................... 163
Metallic Jacket ............................................................................... 164
Filler................................................................................................ 164
Design ............................................................................................ 164
Styles and Applications .................................................................. 164
Gaskets for Heat Exchangers ........................................................ 167
Style 927 Gaskets for Heat Exchangers ........................................ 173
9
Chapter 9 – Metallic Gaskets ............................................. 177
1.
2.
3.
4.
5.
6.
Metallic Gaskets ............................................................................. 177
Flat Metallic Gaskets ..................................................................... 177
Materials ........................................................................................ 178
Finish of the Flange Sealing Surface ............................................. 178
Styles of Flat Metallic Gaskets ...................................................... 178
Ring-Joints ...................................................................................... 183
Chapter 10 – Camprofile Gaskets ...........................................199
1.
2.
3.
4.
5.
6.
7.
8.
9.
Introduction .................................................................................... 199
Materials ........................................................................................ 200
Pressure and Temperature Limits .................................................. 201
Bolting Calculation ......................................................................... 201
Surface Finish................................................................................. 202
Design and Manufacturing Tolerances .......................................... 202
Shapes ............................................................................................ 203
Camprofile Gaskets for Asme B16.5 Flanges ............................... 203
Dimensions nad Tolerances ........................................................... 204
Chapter 11 – Gaskets for Electrical Insulation ...................207
1.
2.
3.
4.
Eletrochemical Corrosion ............................................................... 207
Cathodic Protection ........................................................................ 209
Insulation System for Flanges ........................................................ 209
Specifications for the Gasket Material .......................................... 213
Chapter 12 – Installation and Fugitive Emissions ...............215
1.
2.
3.
4.
5.
6.
7.
Installation Procedure .................................................................... 215
Torque Values................................................................................. 216
Allowable Bolt Stress ..................................................................... 216
Leakage .......................................................................................... 217
Misaligned Flanges ......................................................................... 217
Live Loading ................................................................................... 218
Fugitive Emissions .......................................................................... 221
Chapter 13 – Conversion Factors............................................227
Bibliography ...............................................................................229
10
CHAPTER
1
INTRODUCTION
This book was written with the purpose of providing better design and
application of Industrial Gaskets. It has been very successful in several countries and
has become a reference for gasket applications. This Third English Language Edition,
revised and expanded, incorporates the latest advances in gasket technology since
the last printing.
On analyzing certain leaks - which at first glance seemed to be caused by
gasket deficiencies – we verified, after a more careful observation, that little attention
had been paid to details such as:
• Flange and Gasket design.
• Correct choice of gasket materials.
• Installation procedures.
The great problems confronted by industries such as explosions, fires and
environmental pollution caused by leaks, can be avoided with the correct gasket
design and installation.
The objective of this book is to help prevent accidents by promulgating a
wider understanding of industrial gaskets, specialty sheet packing and spiral wound
gaskets; undoubtedly the types most widely used in industrial applications.
Existing North America market conditions were carefully taken into
consideration. Materials and gasket styles, which are not commercially available or
difficult to find, were omitted; emphasis being given to the most accessible and widely
used products and materials.
This book is divided in chapters that cover the following:
• Design and the New Gasket Constants.
• Non-Metallic Gasket Materials.
• Sheet Packing Gaskets.
• PTFE Gaskets.
• Metallic Gasket Materials.
11
• Spiral Wound Gaskets.
• Jacketed and Heat Exchanger Gaskets.
• Metallic Gaskets.
• Camprofile Gaskets.
• Insulation Gaskets for Flanges.
• Installation Procedures and Fugitive Emissions.
• Conversion Factors.
The most important changes to this Third Edition are:
• The Chapter about PTFE Gaskets has been expanded to include the Tealon*
restructured PTFE gasket sheet.
• New Non-Asbestos Sheet Packing materials.
• Serrated Metallic Camprofile Gaskets for ASME B16.5 flanges
• All tables were revised, updated and expanded.
The author would welcome commentaries and suggestions that can be sent
to Av. Matin Luther King Jr., 8939, 21530-011, Rio de Janeiro, RJ, Brazil.
* Tealon is a trademark of E.I. DuPont De Nemours and Company and is used under
license by Teadit.
12
CHAPTER
2
DESIGN AND THE
NEW GASKET CONSTANTS
1. LEAKS
Based on the fact of the non-existence of “zero leakage”, to determine if a
gasket is leaking or not depends on the method of measurement or on the criterion
utilized. In certain applications the maximum leak index can be, for example, only one
drop of water per second. In other applications it can be the absence of soap bubbles
when the equipment or piping is under pressure. More rigorous conditions can even
call for tests with mass spectrometers or other leak detection equipment.
In order to establish criteria for measuring maximum admissible leakage the
following should be considered:
• Fluid to be sealed.
• Impact on the immediate environment, if fluid escapes into the atmosphere.
• Danger of fire or explosion.
• Other relevant factors in each particular situation.
For industrial applications, “zero leakage” is commonly defined as Helium
leakage between 10-4 and 10-8cm3/sec or less. The Johnson Space Center (NASA) in
Houston, Texas, establishes the value of 1.4 x 10-3cm3/sec of N2 at 300 psi at room
temperature. For reference, we can establish that a drop of liquid has an average
volume of 0.05cm3. Thus 20 drops will be necessary to make 1cm3. This is good
reference value to define the maximum leakage tolerated in industrial applications.
With the need to control fugitive emissions the Environmental Protection
Agency (EPA) has initially set the limit of 500 parts per million (ppm) as maximum leak
for flanges. However this value has been considered too high and there has been a
trend to revise it to 100 ppm.
The leakage rate is a relative concept and in critical situations must be
judiciously established.
13
2. SEALING
If it were technically and economically feasible to manufacture perfectly
smooth and polished flanges and if we could maintain these surfaces in permanent
contact, there would be no need for gaskets. This technical and economic impossibility
results from:
• Size of the vessel and/or the flanges.
• Difficulty in maintaining these surfaces perfectly smooth during the handling
and/or assembling of the vessel or piping.
• Corrosion or erosion of the surface by time.
• To overcome these difficulties, gaskets are used as a sealing element. When
a gasket is seated against the flange surface, it flows, filling the imperfections
between them and providing the necessary sealing. Therefore, in order to
obtain adequate sealing we must consider four factors:
• Seating stress: we must provide an adequate way of seating the gasket so
it will be able to flow and fill the flange imperfections. The minimum initial
seating stress is recommended by the American Society of Mechanical
Engineers (ASME) Pressure Vessel and Boiler Code, which will be explained
later. This seating stress must be limited in order to prevent the destruction
of the gasket by an excess of compression.
• Sealing force: a residual stress on the gasket must be maintained, in order
to keep it in contact with the flange surfaces, thus avoiding leakage.
• Material selection: The gasket material must resist the pressure as well as
the fluid to which it is subjected. The correct selection of materials will be
covered in several chapters of this book.
• Surface finish: There is a recommended flange surface finish for each style
of gasket and class of service. The use of surface finish not compatible
with the gasket is one of the primary causes of leakage.
3. FORCES IN A FLANGED JOINT
The Figure 2.1 shows the forces in a flanged joint.
• Radial force: originated by the internal pressure; it tends to blow out the
gasket.
• Separation force: also originated by internal pressure; it tends to separate
the flanges.
• Bolt load: it is the total load exercised by the bolts.
• Flange load: it is the force, which compresses the flanges against the gasket.
The seating stress initially applied to the gasket, besides causing flow of
the gasket material, must:
• Compensate for the separation force caused by internal pressure.
• Be sufficient to maintain a residual stress on the gasket, avoiding fluid
leakage.
14
From a practical point of view, the residual stress, in order to maintain the
sealing, must be “x” times the internal pressure. This “x” value is known as the factor
“m” in the ASME Code and varies according to the style of the gasket used. The “m”
value is the ratio between the residual stress on the gasket (bolt load minus separation
force) and the internal pressure. The larger the “m” value is, the greater it will be the
system’s security against leakage.
Figure 2.1
4. ASME CODE
The Division 2 Section VIII of the ASME Pressure Vessel and Boiler Code
suggests the equations for gasket design and the “m” (gasket factor) and “y” (minimum
gasket seating stress) values. These values are not mandatory; however they are
based on the results of successful practical applications. The designer has the freedom
to use different values as long as the available data justifies the need for doing so.
The Appendix 2 of the Section VIII requires that a calculation of a bolted
flanged joint be made for two independent conditions: operating pressure and minimum
seating stress.
15
4.1. OPERATIONAL CONDITIONS
This condition determines a minimum bolt load as per the equation:
Wm1 = (π G2 P / 4) + (2 b π G m P) (eq. 2.1)
This equation establishes that the minimum bolt load necessary to fulfill the
operational conditions is equal to the sum of the pressure force plus a residual load
over the gasket times a factor and times the internal pressure. Or, interpreting it in a
different way, this equation establishes that the minimal bolt load must be such that
there always will be a residual pressure applied to the gasket greater than the internal
pressure of the fluid. The ASME Code establishes the minimum values of factor “m”
for diverse styles of gaskets as shown in Table 2.1.
4.2. MINIMUM GASKET SEATING STRESS
The second condition determines a minimum seating gasket stress without
taking into consideration the fluid pressure. This seating force is calculated by the
formula:
Wm2 = π b G y (eq. 2.2)
where “b” is defined as the effective gasket width and “y” is the value of the minimum
seating stress, obtained in Table 2.1. The “b” value is calculated by:
b = b0 when b0 is equal to or less than 1/4" (6.4 mm)
or
b = 0.5 ( b0 ) 0.5 when b0 is greater than 1/4" (6.4 mm)
The ASME Code also explains how to calculate b0 according to the face of the
flange as shown in Tables 2.1 and 2.2.
4.3. BOLT AREA
The minimum bolt area Am must be calculated as follows:
Am1 = (Wm1) / Sb (eq. 2.3)
or
Am2 = (Wm2) / Sa (eq. 2.4)
16
where Sb is the maximum admissible bolt stress at the working temperature and Sa is
the maximum admissible bolt stress at room temperature.
The value of Am should be the greater of the values obtained in equations 2.3
and 2.4.
4.4. BOLT CALCULATION
The bolts should be selected so that the sum of their maximum stress areas is
equal to or greater than Am:
Ab = ( number of bolts ) x ( minimum bolt area, sqin )
Ab should be equal or greater than Am.
4.5. MAXIMUM GASKET STRESS
The maximum stress on the gasket is calculated by the formula:
Sg(max) = (Wm) / ((π/4) (OD2 - ID2) ))
(eq. 2.5)
or
Sg(max) = (Wm) / ((π/4) ( (OD - 0,125)2 - ID2)) ) (eq. 2.6)
Where Wm is the greater of the values obtained in equations 2.1 and 2.2. The
equation 2.5 should be used for spiral wound gaskets and equation 2.6 for other
styles of gaskets.
The Sg value, calculated by equations 2.5 or 2.6, should be less than the
maximum stress, which the gasket can resist. If Sg value is larger, another style of
gasket must be used or, when not possible, the gasket area must be enlarged.
17
Table 2.1
Gasket Factor m and Minimum Design Seating Stress y
Gasket Material
Elastomer - less than 75 Shore A
- 75 Shore A or higher
- with cotton fabric
Sheet Packing
1/8" thick
1/16" thick
1/32" thick
Vegetable Fiber
Spiral Wound Stainless Steel or Monel
Asbestos filled
Corrugated metal Asbestos filled
Aluminum
Copper or Brass
Carbon Steel
Monel
Stainless Steel
Corrugated Metal
Copper or Brass
Carbon Steel
Monel
Stainless Steel
Jacketed Metal Asbestos filled
Aluminum
Copper or Brass
Carbon Steel
Monel
Stainless Steel
Grooved Metal
Aluminum
Copper or Brass
Carbon Steel
Monel
Stainless Steel
Solid Flat Metal Aluminum
Copper or Brass
Carbon Steel
Monel
Stainless Steel
Ring Joint
Carbon Steel
Monel
Stainless Steel
y
(psi)
m
0.50
1.00
1.25
2.00
2.75
3.50
1.75
0
200
400
1600
3700
6500
1100
3.00
10000
2.50
2.75
3.00
3.25
3.50
2.75
3.00
3.25
3.50
3.75
2900
3700
4500
5500
6500
3700
4500
5500
6500
7600
3.25
3.50
3.75
3.50
3.75
3.25
3.50
3.75
3.75
4.25
4.00
4.75
5.50
6.00
6.50
5.50
6.00
6.50
18
flat
Facing
Colunn
Sketch
b0
Table 2.
(la) (lb) (1c)
II
(1d) (4) (5)
flat
(la) (lb) (1c)
(1d) (4) (5)
Gasket
Style
II
flat
(la) (lb) (1c)
(1d) (4) (5)
II
911, 913
914
(la) (1b)
II
926
(la) (1b)
II
900
(la) (1b) (1c)
(1d)
II
(la) (1b) (1c)
(1d) (2)
II
(la) (1b) (1c)
(1d) (2) (3)
II
(la) (1b) (1c)
(1d) (2) (3)
(4) (5)
I
(6)
I
5500
6500
923
7600
8000
9000
5500
6500
7600 941, 942
9000
10100
8800
13000
18000
940
21800
26000
18000
21800 950, 951
26000
19
Table 2.2 (Continued)
Location of Gasket Load Reaction
5. NOTATION
A b = bolt cross-sectional area at the root of the thread or the smallest area under
stress (sqin).
A m = total bolt cross-sectional area. Is considered as the greatest value for Am1 and
Am2 (sqin).
A m1 = total bolt cross-sectional area calculated for operational conditions (sqin).
A m2 = total bolt cross-sectional area necessary to seat the gasket (sqin).
B
= effective gasket width or gasket contact width with the flange surface (in).
b 0 = basic gasket seating width (in).
OD = gasket external diameter (in).
ID = gasket internal diameter (in).
G = diameter of the location of gasket load reaction, Table 2.2 (in).
m = gasket factor, Table 2.1.
N = radial width used to determine the basic width of the gasket, Table 2.2 (in).
20
P
= design pressure (psi).
Sa = maximum allowable bolt stress at room temperature (psi)
Sb = maximum allowable bolt stress at design temperature (psi).
Sg = stress over the gasket surface (psi).
W m = bolt load as the greater of the values Wm1 and Wm2.
Wm1= minimum bolt load for operational conditions (psi).
Wm2= minimum bolt load to seat the gasket (psi).
y
= minimum gasket seating stress (psi).
6.
BOLT TORQUE CALCULATION
6.1. TIGHTENING FACTOR
The frictional force is the principal responsible factor for keeping a bolt
tightened. Suppose we have a spiral thread “unwound” which we represent by an
inclined plane. When a torque is applied to it, the result will be similar to the one
produced by a heavy block pushed up an inclined plane subject to the forces shown
in Figure 2.2.
Figure 2.2
21
Where:
a
d
F
Fa
Fn
k
Np
r
T
u
= inclination angle of the thread.
= bolt diameter.
= bolt load.
= frictional force.
= bolt force perpendicular to the thread.
= tightening factor.
= number of bolts.
= bolt radius.
= torque applied to bolt.
= coefficient of friction
In keeping the balance between the forces acting in parallel direction to the
inclined plane we have:
(T/r) cos a = uFn + Fp sin a
(eq. 2.7)
In the perpendicular direction to the inclined plane, we have:
Fn = Fp cos a + (T/r) sin a
(eq. 2.8)
Since the angle of the thread is very small for ease of calculation we can
ignore the factor (T/r) sin (a) in the equation 2.8. By replacing value Fn in equation 2.7,
we have:
(T/r) cos a = uFp cos a + Fp sin a
(eq. 2.9)
By calculating T value we have:
T = Fp r (u + tg a)
(eq. 2.10)
Since the coefficient of friction is constant for a determined lubrication
condition and since tg(a) is constant for each thread, exchanging r for d,
we have:
T = k Fp d
(eq. 2.11)
Where k is a factor experimentally determined. In Table 2.3 we show k values
for bolts very well lubricated with oil and graphite. Those values are based in practical
tests. Non-lubricated bolts show approximately a 50% difference. Different lubricants
can produce values different from the ones shown in Table 2.3. These values must be
determined in actual tests.
22
6.2. TIGHTENING TORQUE
To calculate the tightening torque we should verify the value of the bolt load
needed Wm1 or Wm2as it has been calculated in equations 2.1 and 2.2. By modifying
equation 2.11, we have:
T1 = (k Wm1 d) / N p (eq. 2.12)
T2 = (k Wm2 d) / N p (eq. 2.13)
The value of T must be the greater of the values obtained in equations 2.12 and
Table 2.3
STEEL OR ALLOY STEEL BOLTS OR STUDS
Nominal Diameter
inches
l/4
5/16
3/8
7/16
l/2
9/16
5/8
3/4
7/8
1
1 1/8
1 1/4
1 3/8
1 1/2
1 5/8
1 3/4
1 7/8
2
Number of Threads Tightening Factor Cross Sectional
per inch
-k
Thread Area - sqin
20
0.027
0.23
18
0.045
0.22
0.068
16
0.18
0.093
14
0.19
0.126
13
0.20
0.162
12
0.21
0.202
11
0.19
0.302
10
0.17
0.419
9
0.17
0.551
8
0.18
0.693
7
0.20
0.890
7
0.19
1.054
6
0.20
1.294
6
0.18
1.515
5 1/2
0.19
1.744
5
0.20
2.049
5
0.21
2.300
4 1/2
0.19
7. SURFACE FINISH
For each style of gasket there is a recommended finish for the flange sealing
surface. This finish is not mandatory, however is based in successful practical
applications.
As a general rule, it is necessary that the surface be serrated for non-metallic
gasket materials like sheet-packing, rubber and PTFE. Metallic gaskets require a
smoother finish. The reason for this difference is that non-metallic materials must be
23
“bitten” by the sealing surface, therefore avoiding an excessive extrusion or expulsion
of the gasket by the radial force.
Solid metallic gaskets require very high force “to flow” the material into the
flange surface. Consequently, the smoother the surface the lesser will be the possibility
of leakage.
Spiral wound gaskets require some degree of superficial roughness in order
to avoid “sliding” under stress. They show a tendency of buckling inwards which is
critical especially with Flexible Graphite filled gaskets.
The style of the gasket, therefore, shall determine the finish of the sealing
surface, and there is no “optimum finish” to fit the diverse styles of gaskets.
The gasket material should always be softer than the flange, so the gasket
will always be seated by the flange, maintaining the finish of the flange surface
unaltered.
7.1. RECOMMENDED FINISH FOR SEALING SURFACES
The flange surfaces can vary from a rough casting finish to polished. However,
the most common commercially available is concentric or phonographic spiral grooves
as shown in Figure 2.3. Both are machined with a tool with a tip radius of 1/16" (1.6 mm)
and 45 to 55 grooves per inch. This is known as a 125 µpol Ra (3.2 µm Ra) to 250 µpol
Ra (6.3 µm Ra) finish.
Figure 2.3
Table 2.4 indicates the type of finish used for industrial gaskets. Per the MSS
SP-6 Standards Finishes for Contact of Pipe Flanges and Connecting-End Flanges of
Valves and Fittings, the Roughness Average (Ra) is expressed in micro-inches or
micrometers. It must be measured by visual comparison.
24
Table 2.4
Finish of the Flange Sealing Surface
Gasket Description
Teadit
Style
Gasket Cross
Section
Surface Finish
Ra
µm
µ pol
Flat Non-Metallic
810
820
3.2 a 6.3
125 a 250
Corrugated Metallic
900
1.6
63
Covered Corrugated Metallic
905
3.2
125
Spiral Wound
911
913
914
2.0 a 6.3
80 a 250
1.6 a 2.0
63 a 80
940
1.6
63
941
1.6
63
942
1.6 a 2.0
63 a 80
1.6
63
920
923
Metal Jacketed
926
927
929
Flat Metallic
Metallic Grooved
Covered Metallic Grooved
(Camprofile)
950
951
Ring-Joint
RX
BX
25
7.2. SURFACE FINISH AND SEALABILITY
Following are some rules, which must be observed in order to harmonize the
surface finish and the style of gasket:
•
•
•
•
•
•
The surface finish has a great influence on the ability to seal.
A minimum stress force must be obtained in order to flow the gasket through the
flange imperfections. A soft gasket (like cork) requires a seating stress lesser than
a denser gasket (like sheet packing).
The seating force is proportional to the flange contact area. It can be reduced by
diminishing the width of the gasket or of the flange contact area.
Whatever the style of gasket or finish used it is important that there are no scratches
or radial tool marks on the sealing surface of the flanges.
Phonographic grooves are more difficult to seal than the concentric ones because
the gasket, when seated, must flow up to the bottom of the grooves. This prevents
any leak path to be formed from one end of the spiral to the other.
Since the materials have different hardness and flow characteristics, the choice of
a type of flange surface finish is going to depend basically on the gasket style
and/or material.
8. PARALLELISM OF SEALING SURFACES
Tolerance for parallelism is shown on Figure 2.4. The right figure is less critical
since the bolt force tends to correct the problem.
Total Deviation:
1+
Figure 2.4
26
2 < = 1/64”
9. WAVINESS OF THE SEALING SURFACES
The maximum deviation of the sealing surfaces depends on the type of gasket
(figure 2.5):
• Sheet packing or rubber gaskets: 0.030 in (0.8 mm)
• Spiral wound gaskets : 0.015 in (0.4 mm)
• Solid metallic gaskets: 0.00 5in (0.1 mm)
Figure 2.5
10. STYLES OF FLANGES
Even though flange design is beyond the scope of this book, in the following
figures we show the most common combinations of flange faces.
10.1. FLAT FACE
Non-confined gasket (Figure 2.6). Contact surfaces in both flanges are flat.
The gasket can be style RF with the external diameter of the gasket touching the bolts.
Or FF with the gasket covering the entire flange surface. Flat flanges are
normally used in flanges made out of fragile materials.
Figure 2.6
27
10.2. RAISED FACE
Non-confined gasket (Figure 2.7). Contact surfaces are raised about 1/16 in
(1.6 mm) or ¼ in (6.4 mm). Normally the gasket covers up the bolts. It allows the
assembly and removal of the gasket without having to separate the flanges, facilitating
maintenance work. This type is used more often in piping.
Figure 2.7
10.3. TONGUE AND GROOVE
Totally confined gasket (Figure 2.8). The groove depth is equal or greater
than the tongue high. The gasket has, usually, the same width as the tongue. It is
necessary to separate the flanges in order to change the gasket. Since this style of
flange exerts high seating stress on the gasket, it is not recommended for non-metallic
gaskets.
Figure 2.8
28
10.4. MALE AND FEMALE
Semi-confined gasket (Figure 2.9). The most common style is the one on the
left. The depth of the female is equal or less than the height of the male in order to
avoid the possibility of direct contact of the flanges when the gasket is compressed.
The female external diameter is up to 1/16 in (1.6 mm) larger than the male. The
flanges must be separated to change the gasket. In the figures at the right and left, the
gaskets are confined by the external diameter. In the center figure it is confined by the
internal diameter.
10.5. FLAT FACE AND GROOVE
Totally confined gasket (Figure 2.10). The external face of one of the flanges
is plain and the other has a groove where the gasket is assembled. They are used in
applications where the distance between flanges must be precise. When the gasket is
seated the flanges touch each other. Only very resilient gaskets can be used in these
type of flanges. Spiral-wound, O-Rings, non-solid metallic, pressure activated and
jacketed with metallic fillers are recommended.
Figure 2.10
29
10.6. RING-JOINT
Also called API Ring (Figure 2.11). Both flanges have channels with walls in
a 23º angle. The gasket is made out of solid metal with an oval or octagonal profile. The
octagonal profile is more efficient.
Figure 2.11
11. THE NEW GASKET CONSTANTS
Traditionally calculations for piping flanges and gaskets use values and
formulas recommended by the American Society of Mechanical Engineers (ASME)
Section VIII of Pressure Vessel and Boiler Code.
The ASME Code recommends values for minimum seating stress “y” and the
maintenance factor “m” for various styles of gaskets. These values were determined
from experimental work in 1943.
With the development of materials like Flexible Graphite, PTFE and the
replacement of asbestos-based gaskets for other materials, it became necessary to
determine the values of “m” and “y” for those new materials. In 1974, the Pressure
Vessel Research Committee (PVRC) initiated an experimental program to better
understand the behavior of a gasket in a flanged joint since there was no analytical
theory that allowed determination of this behavior. This work was sponsored by thirty
institutions among them ASME, American Petroleum Institute (API), Fluid Sealing
Association (FSA), and American Society for Testing Materials (ASTM) among others.
The University of Montreal, Canada, was contracted to conduct the tests,
and present their results and suggestions.
In the course of the research the impossibility of determining the values of
“m” and “y” for the new materials was verified and it was also ascertained that the
values for the traditional materials were not consistent with the experimentally obtained
results.
The researchers then opted to develop, starting from an experimental basis, a
methodology for gasket calculation that was coherent with the practical results. In
this section this new form of calculation is demonstrated.
It is appropriate to point out that the standardization organizations (like ASME, API,
ANSI, etc.) have not yet officially published a method to calculate gaskets using the
30
New Gasket Constants. There is a proposal put forth by the researchers now being
discussed by the ASME.
11.1. GASKET TESTING
The gaskets chosen for testing were the most represented in industry.
• Metallic gaskets flat and corrugated in low carbon steel, soft copper
and stainless steel.
• Metal o-rings.
• Sheet Packing: NBR and SBR binders with asbestos, aramid and glass
fibers.
• Flexible Graphite and PTFE sheets.
• Spiral Wound gaskets in stainless steel asbestos, non-asbestos,
flexible graphite and PTFE fillers.
• Double Jacketed carbon and stainless steel with asbestos and nonasbestos fillers.
The gaskets were tested in the device shown in Figure 2.12.
Figure 2.12
The tests were conducted under three pressures: 100, 200, and 400 psi with
nitrogen, helium, kerosene and water. Sequence of steps followed during the test:
• The initial stress - part A of the chart figure 2.13 -the gasket is
tightened until deflection Dg keeping Sg constant, pressure is
increased to 100 psi and the leak rate Lr is measured.
31
• The same procedure is repeated for 200 and 400 psi.
• The operating stress - part B of the Figure 2.13 - with pressure
constant (100, 200 and 400 psi) Sg is decreased at regular intervals,
deflection, Dg, and leak rate, Lr, are measured.
• This procedure is repeated until Lr exceeds the leak detector
measuring capacity.
• Keeping the pressure constant, Sg is increased measuring Dg and Lr
at regular intervals.
The Figure 2.14 shows an example of the fluid pressure as a function of mass
leak rate for each value of gasket stress.
Figure 2.13
32
Figure 2.14
From experiments conducted at the University of Montreal various
conclusions were reached:
• The gaskets demonstrate similar behavior no matter what style, or
material they are made of.
• The tightness of a gasket is a direct function of the seating stress.
• The non-dimensional Tightness Parameter, Tp, was suggested as the
best way to represent the behavior of the diverse styles of gaskets and
materials.
Tp = (P/P*) x (Lrm*/ (Lrm x Dt))a
where:
0.5 < a < 1.2 being 0.5 for gases and 1.2 for liquids
P = Fluid Pressure (MPa)
P* = Atmospheric Pressure (0.1013 MPa)
Lrm = mass leak rate per unit of diameter (mg/sec-mm)
Lrm* = mass leak rate with 1 mg/sec-mm reference. Normally taken
for a reference gasket with a 150 mm outside diameter.
Dt = gasket outside diameter (mm)
The Tightness Parameter can be defined as the pressure necessary to create
a certain level of leakage. For example a Tp equal to 100 signifies that a pressure of 100
atmospheres (1470 psi or 10.1 MPa) is necessary to create a leak of 1mg/sec in a gasket
with an external diameter of 150 mm (6 in).
By plotting on a scale log-log the experimental values of the Tightness
Parameter in function of the Gasket Stress we have the chart in Figure 2.15.
33
Figure 2.15
From the chart we can establish the Gasket Constants, obtained experimentally,
that determine the gasket behavior. The constants are:
Gb = intersection point of the seating stress line (part A of the test)
a = inclination of the seating stress line
Gs = focal point of the gasket stress relief lines (part B of the test)
In Table 2.5 are the constants obtained in the PVRC study. The ASTM is
developing a method to determine the gasket constants.
34
Table 2.5
Gasket Constants
Gb
(MPa)
Gasket Material
Compressed Asbestos Sheet
1/16" thick
1/8" thick
Compressed Non-Asbestos Sheet 1/16" (1.6 mm) thick
Teadit NA 1001
Teadit NA 1080
Teadit NA 1081
Teadit NA 1100
Expanded PTFE Sheet Teadit 24SH 1/16" thick
Expanded PTFE Cord Teadit 24B
a
Gs
(MPa)
17.240
2.759
0.150
0.380
0.807
0.690
0.938
0.45
5 E-4
0.903
2.945
0.44
0.313
5.4 E-3
3 E-4
8.786
0.193
1.8 E-14
®
Tealon Restructured PTFE Sheet
TF 1570
TF 1580
TF 1590
Flexible Graphite - Graflex
Monolithic - style TJB
Tanged Core - style TJE
Stainless Steel insert - style TJR
Polyester insert – style TJP
244
114
260
0.31 1.28 x 10-2
0.447 1.6 x 10-3
6.3
0.351
6.690
9.655
5.628
6.690
0.384
0.324
0.377
0.384
3.448 E-4
6.897 E-5
4.552 E-4
3.448 E-4
Spiral Wound Gasket Graflex filled
Without inner ring ( style 913 )
With inner ring (style 913 M )
15.862
17.448
0.237
0.241
0.090
0.028
Spiral Wound Gasket PTFE filled
Without inner ring (style 913 )
With inner ring (style 913 M )
31.034
15.724
0.140
0.190
0.483
0.462
Jacketed Gasket Graflex filled
Flat (style 923 )
Corrugated (style 926 )
20.000
58.621
0.230
0.134
0.103
1.586
Flat Metal Gasket (style 940 )
Aluminum
Copper or Brass
10.517
34.483
0.240
0.133
1.379
1.779
35
In Figure 2.16 the chart of a spiral wound gasket with Flexible Graphite filler.
Figure 2.16
11.2. TIGHTNESS CLASS
One of the most important concepts introduced by the PVRC studies is of the
Tightness Class. As it is not possible to have a perfect seal as suggested by the
factors “m” and “y”, the PVRC has proposed the introduction of the Tightness Class
corresponding to three levels of maximum leak rates.
Table 2.6
Tightness Class
Tightness Class
Air, Water
Standard
Tight
Leak Rate ( mg / sec-mm )
0.2 ( 1/5 )
0.002 ( 1/500 )
0.000 02 ( 1/ 50 000 )
Tightness Constant - C
0.1
1.0
10.0
It is possible to have a classification of the different fluids by tightness class,
taking in consideration the danger to the environment, fire hazards, explosions, etc.
Environmental authorities have not published such classification at the time
of the publication of this book.
We can visualize the proposed values with a practical example. A spiral wound
gasket with dimensions per ASME B16.20 for an ASME B16.5 4 in class 150-psi flange,
with a standard tightness class, leaks 0.002 mg/sec-mm. The overall leak of this gasket
is:
36
Leak Rate (Lrm) = 0.002 x outside diameter
Lrm = 0.002 x 149.4 = 0.2988 mg/sec = 1.076 g/hour
As mass leak rate is difficult to visualize, below are some practical tables for
a better understanding.
Table 2.7
Volumetric Equivalent
Fluid
Water
Nitrogen
Helium
Volumetric Equivalent
Mass - mg / seg
Volume - l / h
1
0.036
1
3.200
1
22.140
Table 2.8
Bubble Equivalent
Mass Leak Rate
10-1 mg / sec
10-2 mg / sec
10-3 mg / sec
10-4 mg / sec
Volumetric Equivalent
1 ml each 10 seconds
1 ml a each 100 seconds
3 ml per hour
1 ml each 3 hours
Bubble Equivalent
Constant flow
10 bubbles per second
1 bubble per second
1 bubble each 10 seconds
11.3. JOINT ASSEMBLY EFFICIENCY
Studies show a great variation in the bolt load of each bolt even in situations
where the torque is applied in a controlled form. The PVRC has suggested the
introduction of an Assembly Efficiency Factor as shown in Table 2.9.
Table 2.9
Assembly Efficiency
Tightening Method
Power impact, lever or striker (manual or power) wrench
Accurately applied torque ( ± 3 % )
Simultaneous multiple application of direct stud tension
Direct measurement of stud stress or strain
37
Assembly Efficiency “Ae”
0.75
0.85
0.95
1.00
11.4. BOLT LOAD USING THE PVRC PROPOSED PROCEDURE
The proposed PVRC Method of bolt loading design calculations, to make the
calculation easier, has several simplifications, which can generate values with variations
when compared with exact values. These variations are shown in the Paper “ The
Exact Method”, presented by Mr. Antonio Guizzo, Teadit´s Technical Director, at the
6th Annual Fluid Sealing Association Technical Symposium, Houston, TX, October
1996. The same author has presented at the Sealing Technical Symposium, Nashville,
TN, April 1998, a paper showing the actual experimental results compared with the
expected values from the PVRC proposed procedure. Copies of both papers can be
obtained from Teadit at the address shown at the end of this book.
Important note: The ASME has not approved this method, proposed by the
PVRC. Its use must be carefully applied in order to avoid personal and material injuries
deriving from uncertainties that still exist in its application.
• Determine from Table 2.5, the constants Gb, a, e Gs for the gasket to be
used.
• Determine from Table 2.6, the Tightness Class and the Tightness Constant, C.
• Determine from Table 2.9, the Assembly Efficiency, Ae, in accordance with
the Tightening Method to be used.
• Calculate the Gasket Stress Area, Ag
• Determine from the ASME material tables the bolts allowable stress at the
room temperature: Sa
• Determine from the ASME material tables the bolts allowable stress at the
operating temperature: Sb
• Calculate the area affected by the action of the fluid pressure (Hydrostatic
Area), Ai, according the ASME Code:
Ai = ( π /4 ) G2
G = OD - 2b
b = .5 ( b ) 0.5 or b = bo if bo less than ¼” ( 6.4 mm)
bo = N / 2
where G is the Effective Diameter per the ASME Code. See Tables 2.1 and 2.2.
• Calculate the Minimum Tightness Parameter, Tpmin;
Tpmin = 18.0231 C Pd
where C is the Tightness Constant and Pd is the Design Pressure.
• Calculate the Assembly Tightness Parameter, Tpa. This value of Tpa must
be reached during the seating of the gasket, to assure that the value of Tp,
in operation be equal or higher than Tpmin.
38
Tpa = X Tpmin
were X > = 1.5 ( Sa / Sb)
where Sa is the Bolt Allowable Stress at the room temperature and Sb is the
Bolt Allowable Stress at the operating temperature.
• Calculate the Tightness Parameter ratio:
Tr = Log (Tpa) / Log (Tpmin)
• Calculate the minimum Operating Gasket Stress, S ml. This pressure is
required to resist the Hydrostatic End Force and to maintain on the gasket
sufficient compression to assure the required minimum tightness, T pmin.
Sml = Gs [(Gb / Gs) ( Tpa )a ] (1/Tr)
• Calculate the minimum Gasket Assembly Stress, Sya:
Sya = (Gb / Ae) ( Tpa )a
where Ae is the Assembly Efficiency, from Table 2.9
• Calculate the Seating Design Gasket Stress, Sm2:
Sm2 = [( Sb / Sa )( Sya / 1.5 )] - Pd (Ai / Ag)
where Ag is the gasket contact area with the flange sealing surface.
• Calculate the minimum Bolt Load, Wmo:
Wmo = ( Pd Ai ) + ( Smo Ag )
where Smo is the larger of Sm1, Sm2 or 2 Pd.
• Calculate the minimum Bolt Stress Area, Am:
Am = Wmo / Sb
• Number of bolts:
The actual Bolt Stress Area, Ab, must be equal or larger than Am
39
11.5. EXAMPLE OF CALCULATION BY THE PVRC METHOD
A Spiral Wound Gasket with a Nominal Diameter 6 inches, Pressure Class of
300 psi, dimensions per Norma ASME B16.20, with stainless steel and Flexible Graphite
and Carbon Steel guide ring. Flange with 12 bolts of 1 inch diameter in ASTM AS193B7.
•
•
•
•
•
•
•
•
•
•
•
•
Design Pressure: Pd = 2 MPa (290 psi)
Test Pressure: Pt = 3 MPa (435 psi)
Design Temperature: 450o C, (842 F)
Bolts ASTM AS 193-B7, Allowable Stresses:
Room temperature: Sa = 172 MPa
Operating temperature: Sb = 122 MPa
Quantity: 12 bolts
From Table 2.5:
Gb = 15.862 MPa
a = 0.237
Gs = 0.090 MPa
Tightness Class: standard, Lrm = .002 mg/sec-mm
Tightness Constant: C = 1
Bolting with a Torque Wrench: Ae = 0.75
Gasket Contact Area, Ag:
Ag = ( π /4 ) [(od - 3.2)2 - id2] = 7271.390 sqmm
OD = 209.6 mm
ID = 182.6 mm
• Hydrostatic Area. Ai :
Ai = ( π /4 ) G2 = 29711.878 sqmm
G = (OD - 3.2) - 2b = 194.50 mm
b = b0 = 5.95 mm
bo = N/2 = ((OD - 3.2) - ID)/4 = 5.95 mm
• Minimum Tightness Parameter:
Tpmin = 18.0231 C Pd = 36.0462
• Assembly Tightness Parameter:
Tpa = X Tpmin = 1.5 ( 172 / 122 ) 36.0462 = 76.229
• Tightness Parameter ratio:
Tr = Log (Tpa) / Log (Tpmin) = 1.209
40
• Minimum Gasket Assembly Stress:
Sml = Gs [( Gb / Gs ) ( Tpa )a ] 1/Tr = 15.171 MPa
• Gasket Assembly Stress:
Sya = [ Gb/Ae ] ( Tpa )a = 59.069 MPa
• Seating Design Gasket Stress:
Sm2 = [( Sb / Sa )( Sya / 1.5 )] - Pd (Ai / Ag) = 19.759 MPa
• Minimum Bolt Load:
Wmo = ( Pd Ai ) + ( Smo Ag )
where Smo is the larger value of
Sm1 = 15.171
Sm2 = 19.759
2 Pd = 4
Wmo = ( Pd Ai ) + ( Smo Ag ) = 203 089 N
12. GASKET MAXIMUM SEATING STRESS
Sections 4 and 11 of this Chapter show how to calculate the minimum bolt
load to assure a good sealing. However, as the PVRC studies have shown the more
tightened is the gasket the better is the sealing. If the gasket is installed with the
maximum possible stress, the sealability will also be the best possible for the operating
conditions.
Gaskets damaged by excess torque are also a very frequent problem. For all
gasket styles it is possible to calculate the maximum seating stress, which is the
maximum allowable by the gasket without damaging it.
12.1. GASKET MAXIMUM STRESS CALCULATION PROCEDURE
This procedure can be used to calculate the gasket maximum seating stress.
• Calculate the Gasket Contact Area, Ag.
41
• Calculate the Hydrostatic Area, Ai:
Ai = ( π /4 ) G2
G = OD - 2b
b = .5 ( b ) 0.5 or b = b0 if b0 is less than 1/4” (6.4 mm)
b0 = N/2
where G is the Gasket Effective Diameter.
• Calculate the Hydrostatic End Force, H:
H = Ai Pd
• Calculate the Allowable Bolt Load, Wdisp:
Wdisp = Aml Np Sa
where Aml is the Bolt Stress Area, Np is the number of bolts and Sa is the
room temperature Bolt Allowable Stress.
• Calculate the Maximum Seating Stress, Sya:
Sya = Wdisp / Ag
• Determine the Maximum Gasket Seating Stress recommended by the gasket
manufacturer, Sym.
• The Maximum Seating Stress, Sys, is the lower of the values for Sya and Sym.
• Calculate the Maximum Bolt Load, Wmax:
Wmax = Sys Ag
• Calculate the Minimum Bolt Load, Wmo, as shown in Sections 2 and 11 of
this Chapter.
• If the value for Wmax is less than Wmo the gasket and/or the bolts are not
adequate for the application.
• If Wmax is larger than Wmo the gaskets and bolts are adequate for the
application.
• With the value for the Maximum Bolt Load, it is then possible to calculate
and determine if the value for other flange stresses are within the limits
established by the ASME Code. This calculation is beyond the scope of
this book.
42
12.2. GASKET MAXIMUM STRESS CALCULATION EXAMPLE
From the example in Section 11.5 we can calculate the Maximum Gasket Stress.
• Gasket Contact Area, Ag:
Ag = ( π /4 ) [(OD - 3.2)2 - ID2] = 7271.37 sqmm
OD = 209.6 mm
ID = 182.6 mm
• Calculate the Hydrostatic Area, Ai:
Ai = ( π /4 ) G2 = 29711.8 sqmm
G = (OD - 3.2) - 2b = 194.50 mm
b = b0 = 5.95mm
bo = N/2 = ((OD - 3.2) - ID)/4 = 5.95 mm
• Calculate the Hydrostatic End Force, H:
H = Ai Pd = 29711 x 2 = 59 423 N
• Calculate the Allowable Bolt Load, Wdisp:
Wdisp =Aml Np Sa = 391 x 12 x 172 = 807 024 N
• Calculate the Maximum Seating Stress, Sya:
Sya = Wdisp / Ag = 807 024 / 7271 = 110.992 MPa
• Determine the Maximum Gasket Seating Stress recommended by the gasket
manufacturer, Sym:
Sym = 210 MPa
• The Maximum Seating Stress, Sys, is the lower of the values for Sya and Sym:
Sys = 110 MPa
• Calculate the Maximum Bolt Load, Wmax:
Wmax = Sys Ag = 110 x 7271 = 799 810 N
• Calculate the Minimum Bolt Load, Wmo, as shown in Sections 2 and 11 of
this Chapter:
Wmo = 203 089 N
43
• Since Wmax is larger than Wmo the gaskets and bolts are adequate for the
application.
• With the values for the Minimum and the Maximum Bolt Load we can
calculate the Minimum and the Maximum Bolt Torque:
Tmin = k Wmo dp / Np = 0.2 x 203 089 x 0.0254 / 12 = 85.97 N-m
Tmax = k Wmax dp / Np = 0.2 x 799 810 x 0.0254 / 12 = 338.58 N-m
44
CHAPTER
3
MATERIALS FOR
NON-METALLIC GASKETS
1. MATERIAL SELECTION
The selection of a non-metallic gasket material is difficult due to the existence
in the market of several choices. Materials with similar performance and price are
offered by the manufacturers, which, with the Asbestos replacement have been
developing several alternatives to meet the demand for each application.
It is not practical to list and have the characteristics of all materials. For this
book the most commonly used were listed with their properties. If a deeper knowledge
is required it is recommended to consult with the manufacturer.
The four basic conditions, which must be observed on selecting a gasket
material, are:
• Operating pressure.
• Bolt load.
• Resistance to chemical attack (corrosion)
• Operating temperature.
Operating pressure and bolt load are analyzed in Chapter 2 of this book.
The corrosion resistance can be influenced by several factors, mainly:
• Concentration of the corrosive agent: a greater concentration does not
necessarily make the fluid more corrosive.
• Temperature of the corrosive agent: usually high temperatures accelerate
the corrosion.
45
• Dew point: the fluid excursion through the dew point, in the presence of
sulfur and water frequently found in gases resulting from combustion, can
lead to extremely corrosive condensates.
In critical applications, laboratory tests are necessary in order to determine
the compatibility of the gasket material with the fluid at the operational conditions.
To design a gasket, an evaluation must be done, starting by the type of
flange, bolt load, seating stress, etc. The definition of the style and material of the
gasket must follow all steps. Usually gasket selection can be simplified by using the
Pressure x Temperature Factor, as shown in this Chapter.
2. P x T OR SERVICE FACTOR
The Pressure x Temperature Factor or Service Factor is a good starting point
in the selection of a gasket material. It is obtained by multiplying the pressure in psi
by the temperature in degrees Fahrenheit and comparing the result with the values on
the Table 3.1. If the value is more than 625,000, a metallic gasket must be selected.
Table 3.1
Service Factor
PxT
maximum
15000
40000
75000
400000
625000
Temperature oF
maximum
300
250
500
1000
1100
Gasket material
Rubber
Vegetable fiber
PTFE
Sheet packing
Sheet packing with wire mesh
The temperature limit and the P x T values cannot be taken as absolute values
as with the increase of the operating temperature, the maximum operating pressure
decreases. In each case, conditions such as gasket material, flange design and other
peculiarities of each application have to be evaluated.
Important note: All recommendations of this chapter are generic and the
particular conditions of each case must be carefully evaluated.
3. SHEET PACKING
Since its introduction in the market by the end of last century, sheet packing
has been the most used material in flange sealing. It has the characteristic of sealability
that can be applied to a wide spectrum of operating conditions. Due to its importance
in the field of industrial sealing, the Chapter 4 of this book is entirely dedicated to
sheet packing gaskets.
46
4. POLYTETRAFLUORETYLENE - PTFE
PTFE, because of its exceptional chemical resistance, is the most used plastic
for industrial sealing. The Chapter 5 of this book deals with the several choices of
gaskets with PTFE.
5. FLEXIBLE GRAPHITE - GRAFLEX®
The Flexible Graphite produced from natural graphite has a Carbon content
between 90% to 99.9%.
Graphite flakes are treated with acid, neutralized with water and dried. The
flakes are then subjected to high temperature, and the water, after vaporizing, “explodes”
the flakes, which increase 200 times or more than its original volume. Those expanded
flakes are calendered without any additive or binder, producing sheets of flexible
material.
Flexible Graphite shows low creep defined as a continuous plastic deformation
in a material subject to pressure. Therefore, there is a small loss of bolt load, which
reduces the need for retightening of bolts.
Due to its characteristics, Flexible Graphite is one of the most reliable sealing
materials. If offers excellent resistance to acids, alkaline solutions and organic
composites. However it is not recommended for use in oxidant service in temperatures
above 840 o F (450 o C), the heated Carbon reacts with the Oxygen forming Carbon
Dioxide (CO2). The result of such a reaction is the reduction of the gasket mass and,
consequently of bolt load. Temperature limits: -400o F (-240o C) to 5400o F (3000o C), in
reducing or neutral service without contact with Oxygen. For oxidant service the
upper limit is 840o F (450o C).
The chemical compatibility and temperature limits for several chemical and
organic compounds are shown on Annex 3.1 at the end of this Chapter.
5.1. GRAFLEX® SHEETS
Being a material with low mechanical strength Graflex Flexible Graphite sheets
are supplied with an AISI 316 Stainless Steel or Polyester insert. Sheet dimensions are
1000 mm x 1000 m (39" x 39") and the standard thickness are 0.8 mm (1/32"), 1.6 mm (1/
16") and 3.2 mm (1/8"). The different styles are shown on Table 3.2. It is necessary to
verify the chemical and temperature compatibility of the insert when designing gaskets
with Graflex sheets.
The values for “m” and “y” and the PVRC Gasket Constants are shown on
Table 3.4.
47
Table 3.2
Styles of Graflex® sheets
Style
2660
2661
Bonded AISI
Insert Homogeneous 316L stainless
steel foil
General
Use for General service service, steam,
hydrocarbon
service
2662
AISI 316L
stainless steel
screen
General
service, steam,
hydrocarbon
service
2663
Tanged AISI
316L stainless
steel foil
General service,
steam, hydrocarbon
service, heat
transfer fluids
2664
Polyester foil
General
service, fragile
flanges
Table 3.3
Service Temperature
Temperature ºF
Mínimum
Service
Mínimum
Neutral / reducing
Oxidant
-400
-400
2660
5430
840
2661
870
450
2662
870
450
2663
870
450
Steam
-400
1200
650
650
650
2664
3 000
450
Not recommend
Table 3.4
Gasket Constants
Style
m
y (psi)
Gb (MPa)
a
Gs (MPa)
Maximum
gasket stress (MPa)
2660
1.5
900
6.690
0.384
3.448 E-4
2661
2
1 000
5.628
0.377
4.555 E-4
2662
2
2 800
N/A
N/A
N/A
2663
2
2 800
9.655
0.324
6.897 E-5
2664
1.5
900
6.690
0.384
3.448 E-4
165
165
165
165
165
5.2. GRAFLEX® TAPE
Graflex® can also be used in tapes with or without adhesive backing, flat or
corrugated, 0.4 mm (1/64") thick. The Table 3.5 shows the styles and recommendations
48
Table 3.5
Graflex® Tape
Style
Description
Service
2550
2551
Flat tape adhesive backing
Corrugated tape no adhesive
backing
Piping and connections thread Valve stem packing molded in place
sealant
rings
6. ELASTOMERS
Rubber is very often used in gasket manufacturing due to its sealability
characteristics. In the market there are several types of polymers and formulations,
which allow a great variety of choices.
6.1. PROPERTIES
•
•
•
•
The principal properties that make rubber a good material for gaskets are:
Resilience: rubber is a material with high resilience. Being extremely elastic, it
fills out the flange imperfections even when low stress is applied.
Polymers: there are various polymers with different physical and chemical
characteristics.
Combination of Polymers: the combination of various polymers in a
formulation allows one to obtain different physical and chemical
characteristics such as strength, resistance to chemical attack, hardness, etc.
Variety: sheets or rolls with different thickness, colors, width, length and
surface finishes can be manufactured to fulfill the needs of each application.
6.2. SELECTION PROCESS
Elastomeric gaskets are usually used at low pressure and temperature
applications. In order to improve the mechanical resistance, reinforcement with one or
two layers of cotton lining may be used. Normal hardness for industrial applications is
55 to 80 Shore A and thickness is 0.8 mm (1/32") to 6.4 mm (1/4"). Following there is a
list of elastomers used frequently in industrial gaskets. The ASTM designation is
shown in parentheses. The Annex 3.2 shows the chemical guidelines for elastomer
selection.
49
6.3. NATURAL RUBBER (NR)
The NR rubber offers good resistance to inorganic acids, ammonia, weak
acids and alkali; low resistance to oil, solvents and chemical compounds. It ages due
to ozone attack losing its strength and characteristics; not recommended for use in
applications exposed to sun and oxygen. It has good mechanical and friction resistance
but very limited temperature range: from –60o F (-50o C) to 195o F (90o C).
6.4. STYRENE-BUTADIENE (SBR)
SBR rubber commonly called “synthetic rubber” was developed as an
alternative to the natural rubber. Recommended for service in cold and hot water, air,
steam and some weak acids. It should not be used with strong acids, oils, grease and
chlorates. It offers little resistance to ozone and to the majority of hydrocarbons.
Temperature limits: -60o F (-50o C) to 250o F (120o C).
6.5. CHLOROPRENE (CR)
CR rubber is also known by its commercial name Neoprene (trademark of Du
Pont). It has excellent resistance to oils, ozone, sunlight and aging. Low permeability
to gases. Recommended for use with gasoline and non-aromatic solvents. It offers
little resistance to strong oxidants and to aromatic and chlorate hydrocarbons. Temperature
limits: -60o F (-50o C) to 250o F (120o C).
6.6. NITRILE (NBR)
NBR rubber is also know as Buna-N. It offers good resistance to oils, solvents,
aromatic and aliphatic hydrocarbons and gasoline. Little resistance to strong oxidant
agents, chlorate hydrocarbons, ketones and esters. Temperature limits: -60o F (-50o C)
to 250o F (120o C).
6.7. FLUORELASTOMER (CFM, FVSI, FPM)
It is also known by its commercial name Viton (trademark of Du Pont). It offers
excellent resistance to strong acids, oils, gasoline, chlorate solvents and aliphatic and
aromatic hydrocarbons. Not recommended for use with aminos, esters, ketones and
steam. Temperature limits: -40o F (-40o C) to 400o F (204o C).
6.8. SILICONE (SI)
Silicone rubber offers excellent resistance to the aging process, being
unaffected by sunlight or ozone. For that reason it is often used in hot air. It has little
mechanical resistance. It does not resist aliphatic and aromatic hydrocarbons or steam.
Temperature limits: -150o F (-100o C) to 500o F (260o C).
50
6.9. ETHYLENE-PROPILENE (EPDM)
EPDM rubber has good resistance to ozone, steam, strong acids and alkali.
Not recommended for use with solvents and aromatic hydrocarbons. Temperature
limits: -60o F (-50o C) to 250o F (120o C).
6.10. HYPALON
Hypalon, similar to Neoprene rubber, offers excellent resistance to ozone,
sunlight, chemical products and good resistance to oils. Temperature limits: -150 o F
(-100o C) to 300o F (150o C).
7. CELLULOSE FIBER SHEET
Cellulose fiber sheet is manufactured from cellulose with glue and glycerin
binders. It is often used in sealing oil products, gases and diverse solvents. It is
available in rolls with 0.5 mm (0.20") to 1.6 mm (1/16") thick. Maximum temperature:
250o F (120o C).
8. CORK
Cork grains and rubber is bound to obtain cork compressibility, with the
benefits of synthetic rubber. Largely used when the seating force is limited, as in
flanges made out of thin stamped metallic sheets or fragile materials such as ceramic
or glass. Recommended for service with water, lubricant oils and other oil derivative
products at pressures up to 50 psi (3.5 bar). It offers little resistance to aging and is
not recommended for service with inorganic acids, alkali or oxidant solutions.
Temperature limits: -20o F (-30o C) to 250o F (120o C).
9. FABRIC AND TAPES
Gaskets can be made of Asbestos, Silica, Fiberglass, Ceramic or Aramid fabrics
impregnated with Elastomers like SBR, Chloroprene, Fluorelastomer or Silicone.
To improve the mechanical resistance the fabric may be reinforced with metallic
wire.
Fabrics are folded and molded to form the gaskets. These gaskets are used
mainly for boiler manholes and handholes, oven doors and large ducting access panels.
They can be circular, oval, square or any other form.
Its thickness can be from 10.8 mm (1/32") to 3.2 mm (1/8"). Greater thickness can be
obtained by folding layers.
10. TADPOLE
Fabrics can be rolled around a core as shown in Figure 3.2. The fabrics can be
impregnated with Elastomers. The fabric overlaps the core, forming a flat lip in which
51
holes for bolts can be cut. The circular section offers a reliable sealing for irregular
surfaces subject to frequent opening and closing, such as oven doors and large
ducting access panels.
Figure 3.2
11. CERAMIC FIBER BLANKETS
In the form of blankets it is used to manufacture gaskets for use in hot gases
and low pressure service. This material is also used as filler for metallic gaskets.
Temperature limit: 2190o F (1200o C).
12. CERAMIC FIBER MILLBOARD
Millboards, originally designed as a thermal insulation material, can be cut
into gaskets for low pressure, high temperature ducting systems. Temperature limit:
1450o F (800o C).
13. BEATER ADDITION
The Beater Addition process (BA) used in the manufacture of gasket materials
is similar to the one used in paper manufacture. Synthetic, organic or mineral fibers are
beaten with binders which “open” them, providing a large contact area with the binders.
This enlarged area of contact increases the mechanical resistance of the
product. Several binders can be used such as Nitrile Latex and SBR rubber. Due to its
limited pressure and temperature resistance BA materials are used mainly as fillers for
metallic gaskets. The most common application is the Mica-Graphite filler for low
temperature Spiral Wound gaskets.
Materials produced by the BA process are available in reels up to 48"
(1200 mm) wide with 0.012" (0.30 mm) to 1/16" (1.6 mm) thick.
52
Annex 3.1
GRAFLEX® CHEMICALCOMPATIBILITY*
Maximum Temperature °F (oC)
All
All
All
840 (450)
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
Not recommended
All
All
All
Not recommended
Not recommended
All
All
All
All
All
All
All
All
All
All
Product
Acetic acid
Acetic anhydride 100%
Acetone
Air
Alum
Aluminum chloride
Ammonium bifluoride
Ammonium bisulfate
Ammonium hydroxide
Ammonium sulfate
Ammonium thiocyanate 0 - 63%
Amyl alcohol 100%
Aniline 100%
Aniline hydrochloride 0 - 60%
Arsenic acid
Arsenic trichloride 100%
Benzene 100%
Benzene hexachloride 100%
Benzyl sulfonic acid
Boric acid
Bromine
Bromine water
Butyl alcohol
Butyl cellosolve
Calcium chlorate
Calcium hypochlorite
Carbon tetrachloride 100%
Carbonic acid
Chloral hydrate
Chloroethylbenzene 100%
Chloroform 100%
Citric acid
Copper sulfate
Cupric chloride
Dioxane
Ethyl alcohol
* Please see note at the end of this table
53
Annex 3.1 (continued)
GRAFLEX® CHEMICALCOMPATIBILITY*
Maximum Temperature °F (oC)
All
All
All
All
All
All
Room
All
All
All
Not recommended
All
All
All
All
All
All
All
All
All
All
Not recommended
All
All
All
All
All
All
All
All
All
All
All
All
All
All
Not recommended
Product
Ethyl chloride
Ethyl mercaptan – water
Ethylene chlorohydrin 0-8%
Ethylene dibromide 100%
Ethylene dichloride 100%
Fatty acids
Ferric chloride
Ferrous chloride
Ferrous sulfate
Formic acid
Fluorine
Folic acid
Gasoline 100%
Glycerin
Heat transfer fluids
Hydrogen chloride
Hydrobromic acid
Hydrochloric acid
Hydrofluoric acid
Hydrofluosilicic acid 0-20%
Hydrogen sulfide + water
Iodine
Isopropyl acetate 100%
Isopropyl alcohol
Isopropyl ether 100%
Kerosene 100%
Lactic acid
Manganous sulfate
Mannitol
Methyl alcohol
Methyl isobutyl ketone 100%
Monochloroacetic acid 100%
Monochlorobenzene 100%
Monoethanoamine
Monovinyl acetate
Nickel chloride
Nitric acid
* Please see note at the end of this table
54
Annex 3.1 (Continued)
GRAFLEX® CHEMICALCOMPATIBILITY*
Maximum Temperature °F (oC)
All
All
All
All
All
All
All
Not recommended
All
Not recommended
All
1200 (650)
All
All
All
All
Not recommended
All
All
All
All
All
All
All
Product
Octyl alcohol 100%
Oxalic acid
Paraldehyde 100%
Phosphoric acid 0-65%
Phosphorous trichloride 100%
Refrigerant fluids
Sodium chloride
Sodium chlorite
Sodium hydroxide
Sodium hypochlorite
Stannic chlorite
Steam
Stearic acid 100%
Sulfur dioxide
Sulfur monochloride 100%
Sulfurous acid
Sulfuric acid >70%
Tetrachlorothane 100%
Trichloroetylene 100%
Water
Xylene
Zinc ammonium chloride
Zinc chloride
Zinc sulfate
*NOTE: Properties and application parameters shown throughout this Graflex Chemical
Compatibility Chart are typical. Your specific application should not be
undertaken without independent study and evaluation for suitability. For
specific application recommendations consult with TEADIT. Failure to select
proper sealing products could result in property damage and/or serious
personal injury. Specifications subject to change without notice; this edition
cancels all previous issues.
55
ANNEX 3.2
ELASTOMER RESISTANCE GUIDELINES
1: excellent
2: good
3: fair
4: poor
NBR: Nitrile
FPM : Fluorelastomer
CR : Chloroprene
SBR: Styrene-Butadiene
NR : Natural
SI : Silicone
Service
Diluted ( <10%)
Concentrated
Diluted ( <10%)
Alkali
Concentrated
Aliphatic
Hydrocarbons
Aromatic
Flame propagation
Gas permeability
Aromatic
Gasoline
Non Aromatic
Halogenated solvents
Ketones
Mineral oils
Ozone
Sunlight
Water
Acid
NR
2
3
2
3
4
4
4
3
4
4
4
4
4
4
4
2
SBR
2
4
2
3
4
4
4
3
4
4
4
4
4
4
4
1
CR
3
3
2
2
3
4
1
1
4
2
4
4
3
3
1
4
NBR
2
4
2
3
1
2
4
3
4
3
4
4
1
2
4
1
FPM
1
2
2
4
1
1
2
2
2
2
2
4
1
2
1
3
SI
3
4
3
4
4
4
4
3
4
2
4
4
4
1
1
3
*NOTE: Properties and application parameters shown throughout this Elastomer
Resistance Guidelines are typical. Your specific application should not be
undertaken without independent study and evaluation for suitability. For
specific application recommendations consult with TEADIT. Failure to select
proper sealing products could result in property damage and/or serious
personal injury. Specifications subject to change without notice; this edition
cancels all previous issues.
56
CHAPTER
4
COMPRESSED NON-ASBESTOS
GASKETS SHEETS
1. TEADIT COMPRESSED NON-ASBESTOS GASKETS SHEETS
Manufactured by vulcanization under pressure of mineral or synthetic fibers
with a combination of elastomers. Because of its low cost compared with performance
it is the product most used to fabricate industrial gaskets. Because of its manufacturing
process it is also known as Compressed Sheet. Sheet Packing covers an ample spectrum
of applications.
Its major characteristics are:
• High resistance to seating stress.
• Low creep relaxation.
• Wide range of operating temperatures and pressures.
• Resistance to an extensive range of chemical products.
2. FIBERS
Fibers provide the structural function and give the high mechanical resistance
characteristic of Compressed Sheet. The most used fibers are Asbestos, Glass, Aramid,
Carbon and Cellulose.
In Asbestos based sheets the problem of personal hazard for the user is
reduced because the fibers are mixed and bonded with rubber. However it is necessary
to use any Asbestos product properly; any scraping, filling or other dust generating
processes should be avoided.
57
3. ELASTOMERS
The Elastomer, vulcanized under pressure with fibers, determines the chemical
resistance of Compressed Sheet. They also give the flexibility and elastic properties.
The most used elastomers are:
• Natural Rubber (NR): a natural product extracted from tropical plants, it
has excellent elasticity, flexibility. It has low resistance to chemical products and high
temperature.
• Styrene-Butadiene Rubber (SBR): also known as synthetic rubber, was
developed as an alternative for natural rubber and has similar properties.
• Chloroprene (CR): better known by its commercial name Neoprene. It offers
excellent resistance to oil, gasoline, and ozone.
• Nitrile Rubber (NBR): better chemical and temperature resistance when
compared to SBR and CR rubbers. It has excellent resistance to oils, gasoline, aliphatic
and aromatic hydrocarbonates as well as animal and vegetable oils.
• Hypalon: it has excellent chemical resistance as well as resistance to acids
and alkali.
4. WIRE MESH
A wire mesh is used to increase the compression resistance. Sheets with wire
mesh are recommended where it is necessary to have high mechanical strength. The
wire mesh is usually made of carbon steel. However for corrosive service it can be of
stainless steel.
Sheet Packing with wire mesh insertion has less sealability because the sheet/
mesh interface increases the leak rate of the gasket. It also makes it more difficult to
cut the gasket. Its use should be avoided.
5. FINISHING
The several styles of Teadit Compressed Sheets are manufactured with three
surface finishes, all of them Teadit branded:
• Natural: produces greater adherence to the flange.
• Graphite: avoids adherence to the flange; it is used when the gasket is
frequently replaced.
• Anti-sticking: if graphite cannot be used, another anti-sticking product
such as silicone is used.
6. SHEET DIMENSIONS
Teadit Compressed Sheets are available in the following sizes:
• 59 in (1500 mm) by 63 in (1600 mm).
• 59 in (1500 mm) by 126 in (3200 mm).
• 118 in (3000 mm) by 126 in (3200 mm).
58
The thickness range is from 1/64 in (0.4 mm) up to 1/8 in (3.2 mm). Some styles also are
available in thickness up to 1/4 in (6.4 mm).
7. PHYSICAL CHARACTERISTICS
Standardization organizations have issued several standards to assure
product consistency and uniformity, as well as to compare products from different
manufacturers. The most common physical tests are shown below:
7.1.1. COMPRESSIBILITY AND RECOVERY
Measured according the ASTM F36A. The compressibility is the thickness
reduction when the material is compressed by a load of 5000 psi (34.5 MPa). It is
expressed as percentage of the original thickness.
The recovery is the increase in thickness after the load removal. It is expressed
as percentage of the compressed thickness. Compressibility indicates the capacity of
the material to flow and fill up flange imperfections. A higher compressibility material
is easier to seat.
The recovery indicates the material capacity to resist pressure and temperature
changes.
7.1.2. SEALABILITY
Sealability is measured according the ASTM F37. It indicates the material’s
sealing performance under controlled conditions with Isooctane at 14.7 psi (0.101
MPa) and a seating stress from 125 psi (0.86 MPa) to 4000 psi (27.58 MPa).
7.1.3. TORQUE RETENTION
The torque retention is measured according the ASTM F38. It indicates how
the material retains the bolt load as a function of time. It is expressed as a percentage
of the initial load. A stable sheet will retain a high residual load. On the opposite, an
unstable sheet will show a continuous loss of load and consequently a loss of
sealability. The test parameters are initial load 3045 psi (21 MPa), temperature 212ºF
(100ºC) for 22 hours.
An increase in the sheet thickness or in the service temperature decreases
the torque retention.
7.1.4. FLUID IMMERSION
It is used to determine changes in the material when in contact with fluids in
controlled conditions of temperature and pressure. The standard used is ASTM F146.
The most used fluids are ASTM No. 3 Petroleum based oil and ASTM Fuel B which is
70% Isooctane and 30% Toluene. After the immersion, the compressibility, recovery,
59
increase in thickness, tensile strength and increase in volume results are compared
with values before the immersion.
7.1.5. TENSILE STRENGTH
The tensile strength is measured according the ASTM F152. It is used as a
quality control parameter in sheet manufacturing. Its values are not directly related to
the gasket sealability.
7.1.6. IGNITION LOSS
Measured according ASTM F495 it indicates the material loss of mass with
the temperature.
7.1.7. PRESSURE X TEMPERATURE DIAGRAMS
There is no internationally recognized standard to measure Compressed Sheet
operational limits of pressure and temperature. The Teadit Research and Development
Laboratory has developed a procedure to determine the maximum recommended
operating pressure as a function of the service temperature. The test fluid is Nitrogen.
8. DESIGN
8.1. OPERATIONAL CONDITIONS
To initiate a gasket design it is necessary to verify the operating conditions.
The service pressure and temperature must be compared with maximum values
recommended for the material to be used.
Then the Service Factor is calculated by multiplying design pressure in psi
by temperature in ºF. The value is then compared with the maximum valves indicated
by the manufacturer.
Because the Service Factor is not constant along the temperature range of
material, Teadit has developed the Pressure x Temperature for its Compressed Sheet.
To verify if the material is adequate for the service conditions the design pressure and
temperature must be within the recommended range. If the operating conditions fall
between the curves other factors such as the product to be sealed and thermal cycle
have to be examined. Consult with Teadit since the material may not be recommended
for the application.
8.2. CHEMICAL RESISTANCE
Before deciding on the use of a specific style Compressed Sheet it is necessary
to verify its chemical resistance to the fluid to be sealed. The Annex 4.2 at the end of
this Chapter shows the compatibility for several products and Teadit sheets.
60
Important: the recommendations of the Annex 4.2 are generic and the operating
conditions of the application must be verified before using a specific material.
8.3. ASME FLANGE GASKET DIMENSIONS
The ASME B16.21 Non-Metallic Gaskets for Pipe Flanges shows gasket
dimensions for use in several ASME standard flanges, including the B16.5 flanges,
the most used in industrial applications. Annexes 4.3 to 4.10 have the gasket dimensions
for ASME flanges. The gaskets can be of two styles: Raised Face or Full Face. It is
recommended to use the style RF whenever possible since it is more economical and
allows greater seating stress with the same bolt load.
8.3.1. RAISED FACE (RF)
Raised face (RF): the outside diameter reaches as far as the bolts (Figure 4.1).
Figure 4.1
8.3.2. FULL FACE (FF)
Full face or flat face (FF): the gasket outside diameter is equal to the flange
outside diameter (Figure 4.2).
Figure 4.2
61
8.4. GASKETS FOR HEAT EXCHANGERS
It is very common to use Compressed Sheet gaskets in Shell and Tube Heat
Exchangers. Due the small flange width of their tongue and groove flange facings, it is
recommended to control the maximum seating pressure, to avoid crushing the gasket.
8.5. DIN FLANGE GASKET DIMENSIONS
Dimensions for DIN Flanges are shown in Annex 4.11.
8.6. NON STANDARD FLANGES
The use of Compressed Sheet gaskets in non-standard flanges is very frequent
as in heat exchangers, reactors and other equipment. In this case, design
recommendations of the Chapter 2 must be carefully observed.
9. MANUFACTURING TOLERANCES
The manufacturing tolerances based on the ASME B16.21 are shown on Table 4.1.
Table 4.1
Manufacturing Tolerances
Dimension
External Diameter
Internal Diameter
Tolerance - mm (in)
Up to 300 mm (12")
+0
-1.5 (0.06)
More than 300 mm (12")
+0
-3.0 (0.12)
Up to 300 mm (12")
± 1.5 (0.06)
More than 300 mm (12")
± 3.0 (0.12)
Bolt Circle
Bolt holes center to center
± 1.5 (0.06)
± 0.8 (0.03)
10. LARGE DIAMETER GASKETS
When the gasket dimensions are larger than the sheet or when manufacturing
in sections is recommended for economical reasons, two kinds of splicing are used:
dovetail and bevelled.
10.1. DOVE-TAIL GASKETS
This splice is more frequently used in industrial applications. It can be used
to make gaskets of almost any size or thickness (Figure 4.3). Each section of male and
female is adjusted in such a way as to have a minimum gap between the mating parts.
It is recommended that the gasket is produced as follows:
62
Gaskets with a flange width ( L ) equal or less than 8" (200 mm):
A = B = C = (.3 a .4 ) L
Gaskets with a flange width ( L ) more than 8" (200 mm):
A = (.15 to .2 ) L
B = (.15 to .25 ) L
C = (.25 to .3 ) L
Figure 4.3
10.2. BEVELLED SPLICE
When the seating stress is not adequate for dove tailed gaskets, bevelled
and glued splices can be used (Figure 4.4). Due to manufacturing difficulty, this style
of splicing can only be used for gaskets with a minimum thickness of 1/8 in (3.2 mm).
Figure 4.4
63
11. GASKET THICKNESS
The ASME Code recommends three thicknesses for industrial applications:
1/32 in (0.8 mm), 1/16 in (1.6 mm) and 1/8 in (3.2 mm).
To specify the gasket thickness it is necessary to know the roughness of the
flange sealing surface. As a general rule it is recommended that the gasket should be as
thin as possible but capable of filling out flange irregularities. Experience recommends the
thickness to be equal to four times the groove depth. Thickness above 1/8 in (3.2 mm)
must be used only when strictly necessary. In very worn out, twisted or in large dimension
flanges, thickness of up to 1/4 in (6.4 mm) can be used.
In smooth or polished flanges the minimum possible thickness should be used.
But because there are no grooves or irregularities to “bite” the gasket, it can be expelled
by the radial force.
12. BOLT LOAD
The bolt load must be calculated according to recommendations in Chapter 2 of
this book. The bolt load should not produce an excessive seating stress crushing the
gasket. At the room temperature the Maximum Seating Stress is 30,000 psi (210 MPa) for
1/16 “ (1.6 mm) thick gaskets. The maximum bolt load reduces as the thickness increases.
Table 4.2 shows the Gasket Constants for ASME calculations.
Table 4.2
Gasket Constants
Style
1/16”
m
1/8”
1/16”
y (psi)
1/8”
Gb (MPa)
a
Gs (MPa)
NA 1001
2
2
3500
3500
0.697
0.45
1 x 10-4
NA 1080
3.2
3.8
3500
5000
7.4
0.264
0.0179
NA 1081
2.2
2.2
4000
4000
20
0.203
0.0124
NA 1100
2.9
4.1
3500
3500
0.903
0.44
5.4 x 10-3
13. GASKET FINISH
Natural finish is used the most. The use of anti-sticking compounds such as
graphite, silicone, oils or greases decrease the friction with the flanges making sealing
more difficult and decreasing resistance to high pressure.
A graphite finish should be used only when removal of the gasket is frequent.
Graphite finish on both sides is used for high temperature service. The graphite
increases the superficial heat resistance.
64
14. FINISH OF THE FLANGE SEALING SURFACE
The flange surface finish in contact with the gasket should be rough to “bite”
the gasket. Either concentric or phonographic serrated grooves recommended by the
ASME B16.5 or MSS SP-6 Standards, usually found in commercial flanges, are
acceptable. They are made with a rounded tip tool with a radius of 1/16 in (1.6 mm) or
greater, with 45 to 55 grooves per inch. The resulting roughness is 125 min (3.2 mm) Ra
to 250 min (6.3 mm) Ra.
Concentric 90 degree “V” grooves with a pitch of .025" (0.6 mm) to 0.040 in
(1.0 mm) are also acceptable.
Flanges with phonographic grooves are more difficult to seal. A leak path
may result if the seating stress does not flow the gasket material up to the root of the
grooves.
Radial tool marks or scratches are difficult to seal and must be avoided.
15. STORAGE
Sheet Packing as well as finished gaskets should not be stored for long periods
of time. The elastomer used as a binder ages changing its physical characteristics.
A dry cool place without direct solar light should be used for storage. Direct
contact with water, oil and chemicals should to be avoided. Sheets and gaskets must
be kept preferably flat, without folds or wrinkles. Also it is recommended not to hang
or roll them in order to prevent permanent deformations.
16. TEADIT COMPRESSED NON-ASBESTOS GASKET SHEETS
Teadit Compressed Non Asbestos Gasket Sheets for industrial applications
available at the time of the publication of this book are shown in this Section. Being a
product in continuous development new formulations are often offered, please consult
with Teadit for special application requirements.
16.1. NA 1001 NBR, Aramid Fiber Sheet
Style NA-1001 is a compressed non-asbestos sheet gasket produced from a
combination of aramid and other fibers and bonded with Nitrile Rubber (NBR).
It has numerous applications in the process industries and in water and
wastewater industries. Style NA1001 is suitable for service handling the
following general media categories: mild acids; alkalies; water; brine; air;
industrial gases; animal and vegetable oils; petroleum and derivates; neutral
solutions and refrigerants
Color: green or white.
ASTM line call out - F104: F712120E22M5.
65
NA 1001 Pressure x Temperature diagram
16.1. NA 1080 SBR, Aramid Fiber Sheet
Style NA-1080 is a compressed non-asbestos gasket sheet produced from aramid
fibers, reinforced fillers and bonded with styrene butadiene rubber (SBR). Style
NA1080 is a high quality general service sheet product with excellent sealability
and creep relaxation characteristics. It is especially recommended for hot water
and steam service. In addition, Style NA1080 is suitable for service handling the
following general media categories: mild acids; diluted alkalies; water; brine;
saturated steam; air; industrial gases; neutral solutions and refrigerants
Color: white.
ASTM line call out - F104: F712940E44M5.
NA 1080 Pressure x Temperature diagram
66
16.1. NA 1081 NBR, Aramid Fiber Sheet
Style NA1081 is a compressed non-asbestos gasket sheet produced from a
combination of aramid fiber, inorganic fillers and bonded with Nitrile Rubber
(NBR). Style NA1081 has numerous applications in the process industries
handling media like: mild acids and alkalis, water, hydrocarbons, oils, gasoline,
steam, air, industrial gases, general chemicals, neutral solutions.
Color: blue.
ASTM line call out - F104: F712120E23M5
NA 1081 Pressure x Temperature diagram
16.1. NA 1082 NBR, Aramid Fiber Sheet
Style NA1082 is a compressed non-asbestos sheet gasket sheet produced from
a combination of aramid, inert and reinforced fillers and bonded with Nitrile
Rubber (NBR). Style NA1082 is a high performance sheet that has numerous
applications in the process industries handling media like: mild acids and alkalis,
water, hydrocarbons, oils, gasoline, steam, air, industrial gases, general
chemicals, neutral solutions.
Color: gray.
ASTM line call out - F104: F712120E12M5
NA 1082 Pressure x Temperature diagram
67
16.1. NA 1085 Hypalon, Aramid Fiber Sheet
Style NA1085 is a compressed non-asbestos sheet gasket sheet produced from
a combination of aramid fibers, reinforced fillers, PTFE and bonded with
Hypalon® rubber. Style NA1085 is a severe service non-asbestos sheet that is
specifically formulated to provide an effective seal against most acids in the
process industries. Style NA 1085 is suitable for service handling the following
general media categories: mild acids, strong acids, alkalies, water, brine, air.
Color: cobalt blue.
ASTM line call out - F104: F712000E00M5
NA 1085 Pressure x Temperature diagram
68
16.1. NA 1100 NBR, Carbon Fiber Sheet
Style NA-1100 is a compressed non-asbestos gasket sheet produced from
Carbon fibers and Graphite bonded with Nitrile Rubber (NBR). Style NA 1100 is
a premium grade, multi-service gasket sheet, designed to handle the extremes of
pressure and temperature, and it cuts very easily and cleanly. The versatility of
this sheet enables a plant to standardize on one sheet for a multitude of
applications and avoid the confusion of having to choose from several different
sheets. NA1100 is suitable for service handling the following general media
categories: mild acids, alkalies,water, brine, saturated steam, solvents, neutral
solutions, refrigerants, air, industrial gases, oils, petroleum and derivatives
Color: black.
ASTM line call out - F104: F712120E23M6.
NA 1100 Pressure x Temperature diagram
69
Continuous
Service
Maximum
Pressure Limit
Continuous
Service
Density
Compressibility – ASTM F36A - %
Recovery – minimum - ASTM F36A - %
psi
Tensile Strain Across Grain ASTM F152
Sealability –
MPa
ASTM F37 – ml/h
ASTM IRM 903
Fuel B
ASTM IRM 903
Weight Increase – max
ASTM F 146 - %
Fuel B
Creep Relaxation ASTM F 38 - %
Thickness Increase –
max – ASTM F 146 - %
NA 1100
Maximum
NA 1082
Temperature Limit
F
C
o
F
o
C
o
F
o
C
psi
bar
psi
bar
lb/ft 3
g/cm 3
o
NA 1081
o
Minimum
NA 1080
Physical Properties
NA 1001
Annex 4.1
Physical Properties – Teadit Compressed Non-Asbestos Sheet Materials*
-40
-40
750
400
460
240
1595
110
725
50
109
1.75
7-17
45
1670
11.5
0.25
12
10
15
15
25
-40
-40
720
380
520
270
1015
70
725
50
122
1.96
7-17
45
2030
14
0.25
40
20
30
30
22
-40
-40
750
400
500
260
1595
110
725
50
120
1.92
7-17
50
1820
12.5
0.2
15
15
15
15
22
-40
-40
750
400
500
260
1595
110
725
50
122
1.95
5-15
50
1740
12
0.2
15
10
15
10
20
-40
-40
840
450
520
270
1900
130
1015
70
103
1.65
5-15
50
2175
15
0.2
15
15
15
15
22
*NOTE: Values shown throughout this Compressed Non Asbestos Sheets Physical
Properties Table are typical. Your specific application should not be undertaken
without independent study and evaluation for suitability. For specific application
recommendations consult with TEADIT. Failure to select proper sealing
products could result in property damage and/or serious personal injury.
Specifications subject to change without notice; this edition cancels all previous
issues.
70
NA 1085
Annex 4.1 (Continued)
Physical properties – Teadit Compressed Non-Asbestos Sheet Materials*
Physical Properties
o
Minimum
Temperature Limit
Maximum
Continuous
Service
Maximum
Pressure Limit
Continuous
Service
Density
F
C
o
F
o
C
o
F
o
C
psi
bar
psi
bar
lb/ft 3
g/cm 3
o
Compressibility – ASTM F36A - %
Recovery – minimum - ASTM F36A - %
psi
Tensile Strain Across Grain ASTM F152
Sealability –
MPa
ASTM F37 – ml/h
H 2SO 4 @ 25% concentr.
HCl @ 25% concentr.
HNO 3 @ 25% concentr.
H 2SO 4 @ 25% concentr.
Weight Increase
HCl @ 25% concentr.
with acids –
max - %
HNO 3 @ 25% concentr.
Creep Relaxation ASTM F 38 - %
Thickness
Increase with
acids – max - %
-40
-40
460
240
390
200
1015
70
725
50
106
1.70
5-15
40
2030
14
0.2
6
5
6
6
5
6
26
*NOTE: Values shown throughout this Compressed Non Asbestos Sheets Physical
Properties Table are typical. Your specific application should not be undertaken
without independent study and evaluation for suitability. For specific application
recommendations consult with TEADIT. Failure to select proper sealing
products could result in property damage and/or serious personal injury.
Specifications subject to change without notice; this edition cancels all previous
issues.
71
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Acetaldehyde
B
B
C
B
Acetamide
A
C
B
A
Acetic Acid (T< 90ºC)
A
A
A
A
Acetic Acid (Te” 90ºC)
C
C
A
C
Acetone
C
B
B
C
Acetylene
A
A
B
A
Adipic Acid
A
B
A
A
Air
A
A
A
A
Aluminum Acetate
A
A
A
A
Aluminum Chloride
A
A
A
A
Aluminum Sulfate
A
B
A
A
Ammonia – Cold (Gas)
A
A
A
A
Ammonia – Hot (Gas)
C
C
B
C
Ammonium Carbonate
C
A
C
C
Ammonium Chloride
A
A
A
A
Ammonium Hydroxide 30% (T<50ºC)
A
C
A
A
Amyl Acetate
B
B
C
B
Aniline
C
B
C
C
Barium Chloride
A
A
A
A
Benzene
C
C
C
C
Fluid
* Please see note at the end of this table.
72
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Benzoic Acid
B
B
B
B
Boiler Feeder Water
A
A
A
A
Boric Acid
A
A
A
A
Brines
A
A
A
A
Butadiene
C
C
B
C
Butane
A
C
A
A
Butanone (MEK)
C
C
C
C
Butyl Acetate
B
C
C
B
Butyl Alcohol (Butanol)
A
A
A
A
Calcium Chloride
A
A
A
A
Calcium Hydroxide (T<50ºC)
A
A
A
A
Calcium Hypochlorite
B
C
A
B
Carbon Dioxide
A
A
A
A
Carbon Disulfide
C
C
C
C
Carbon Tetrachloride
B
C
C
B
Castor Oil
A
A
A
A
Chlorine (Dry)
B
B
B
B
Chlorine (Wet)
C
C
C
C
Chlorine Dioxide
C
C
C
C
Chloroform
C
C
C
C
Chromic Acid
C
C
C
C
Fluid
* Please see note at the end of this table.
73
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Citric Acid
A
A
A
A
Condensate
A
A
A
A
Copper Sulfate (T<50ºC)
A
A
A
A
Creosote
A
C
C
A
Cresol
B
C
C
B
Cyclohexane
A
C
C
A
Cyclohexanone
C
C
C
C
Cyclohexyl Alcohol
A
C
B
A
Decane
A
C
C
A
Diesel Oil
A
C
B
A
Dimethylformamide
C
C
C
C
Dowtherm
C
C
C
C
Ethane
B
B
B
B
Ethyl Acetate
C
C
C
C
Ethyl Alcohol (Ethanol)
A
A
A
A
Ethyl Chloride
B
C
C
B
Ethyl Ether
B
C
B
B
Ethylene
A
B
C
A
Ethylene Glycol
A
A
A
A
Formaldehyde
A
B
B
A
Formic Acid
B
A
A
B
Fluid
* Please see note at the end of this table.
74
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Freon 12
A
A
A
A
Freon 22
C
A
A
C
Freon 32
A
A
A
A
Gasoline
A
C
C
A
Glycerin
A
A
A
A
Glycol
A
A
A
A
Grease
A
C
C
A
Heptane
A
C
B
A
Hexane
A
C
A
A
Hydraulic Oil – Petroleum Base
A
C
B
A
Hydrochloric Acid 10%
A
C
A
A
Hydrochloric Acid 37%
C
C
A
C
Hydrofluoric Acid
C
C
C
C
Hydrogen
A
A
A
A
Hydrogen Peroxide <30%
A
B
B
A
Isooctane
A
C
A
A
Isopropyl Alcohol
A
A
A
A
Kerosene
A
C
C
A
Fluid
* Please see note at the end of this table.
75
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Lactic Acid 50%
A
A
A
A
Magnesium Chloride
A
A
A
A
Magnesium Hydroxide (T<50ºC)
B
B
A
B
Magnesium Sulfate
A
A
A
A
Maleic Acid
A
C
C
A
Methane
A
C
B
A
Methyl Alcohol (Methanol)
A
A
A
A
Methyl Chloride
C
C
C
C
Mineral Oil
A
C
B
A
Naphtha
A
C
C
A
Natural Gas - GLP
A
B
A
A
Nitric Acid ≤50% (T<50ºC)
C
C
A
C
Nitric Acid >50%
C
C
C
C
Nitrobenzene
C
C
C
C
Nitrogen
A
A
A
A
Octane
A
C
C
A
Oleic Acid
A
C
B
A
Oxalic Acid
B
B
B
B
Oxygen
C
C
B
C
Ozone
C
C
A
C
Fluid
* Please see note at the end of this table.
76
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Palmitic Acid
A
B
B
A
Pentane
A
C
B
A
Perchloroethylene
B
C
C
B
Petroleum
A
B
B
A
Petroleum Ether
A
C
A
A
Phenol
C
C
C
C
Phosphoric Acid
B
C
C
B
Potassium Acetate
A
B
C
A
Potassium Chloride
A
A
A
A
Potassium Dichromate
A
B
A
A
Potassium Hydroxide (T<50ºC)
B
B
A
B
Potassium Nitrate
A
B
A
A
Potassium Permanganate
A
B
B
A
Propane
A
C
B
A
Propylene
C
C
C
C
Pyridine
C
C
C
C
Sea Water
A
A
A
A
Silicone Oil
A
A
A
A
Sodium Bicarbonate
A
B
A
A
Sodium Bisulfite
A
A
A
A
Sodium Carbonate
A
A
A
A
Sodium Chloride (T<50ºC)
A
A
A
A
Sodium Hydroxide (T≥50ºC)
C
C
C
C
Sodium Hydroxide (T<50ºC)
B
B
A
B
Fluid
* Please see note at the end of this table.
77
Annex 4.2
Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable
B: Consult with TEADIT
C: Not recommended
NA1001
NA1080
NA1085
NA1081
NA1082
NA1100
Sodium Silicate
A
A
A
A
Sodium Sulfate
A
A
A
A
Sodium Sulfide
A
A
A
A
Steam
A
A
B
A
Stearic Acid
A
A
B
A
Styrene
C
C
C
C
Sulfur Dioxide
C
B
A
C
Sulfuric Acid, oleum
C
C
C
C
Sulfuric Acid d” 90%
C
C
A
C
Sulfuric Acid 95%
C
C
B
C
Sulfurous Acid
B
B
A
B
Tannic Acid
A
A
A
A
Tartaric Acid
A
A
A
A
Tetrachloroethene
B
C
C
B
Toluene
C
C
C
C
Transformer Oil
A
C
B
A
Trichlorotrifluoroethane
A
C
C
A
Triethanolamine – TEA
B
B
A
B
Turpentine
A
C
C
A
Water
A
A
A
A
Xylene
C
C
C
C
Fluid
*NOTE: Properties and application parameters shown throughout this Compressed Non Asbestos
Sheets Chemical Compatibility Chart are typical. Your specific application should not
be undertaken without independent study and evaluation for suitability. For specific
application recommendations consult with TEADIT. Failure to select proper sealing
products could result in property damage and/or serious personal injury. Specifications
subject to change without notice; this edition cancels all previous issues.
78
Annex 4.3
FF and RF gasket dimensions per ASME B16.21 for ASME 16.5 flanges
Pressure Class 150 and 300 psi - dimensions in inches
Outside Diameter
Bolt Circle
No. of Bolts
Hole Diameter
Nominal
Inside
Style
Diameter
Diameter 150 psi 300 psi 150 psi 300 psi 150 psi 300 psi 150 psi 300 psi
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
3 1/2
4
5
6
8
10
12
14
16
18
20
24
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
0.84
1.06
1.31
1.66
1.91
2.38
2.88
3.50
4.00
4.50
5.56
6.62
8.62
10.75
12.75
14.00
16.00
18.00
20.00
24.00
3.50
1.88
3.88
2.25
4.25
2.62
4.63
3.00
5.00
3 .38
6.00
4.12
7.00
4.88
7.50
5.38
8.50
6.38
9.00
6.88
10.00
7.75
11.00
8.75
13.50
11.00
16.00
13.38
19.00
16.13
21.00
17.75
23.50
20.25
25.00
21.62
27.50
23.88
32.00
28.25
3.75
2.12
4.62
2.62
4.88
2.88
5.25
3.25
6.12
3.75
6.50
4.38
7.50
5.12
8.25
5.88
9.00
6.50
10.00
7.12
11.00
8.50
12.50
9.88
15.00
12.12
17.50
14.25
20.50
16.62
23.00
19.12
25.50
21.25
28.00
23.50
30.50
25.75
36.00
30.50
2.38
2.62
4
4
0.62
0.62
2.75
3.25
4
4
0.62
0.75
3.12
3.50
4
4
0.62
0.75
3.50
3.88
4
4
0.62
0.75
3.88
4.50
4
4
0.62
0.88
4.75
5.00
4
8
0.75
0.75
5.50
5.88
4
8
0.75
0.88
6.00
6.62
4
8
0.75
0.88
7.00
7.25
8
8
0.75
0.88
7.50
7.88
8
8
0.75
0.88
8.50
9.25
8
8
0.88
0.88
9.50
10.62
8
12
0.88
0.88
11.75
13.00
8
12
0.88
0.88
14.25
15.25
12
16
1.00
1.12
17.00
17.75
12
16
1.00
1.25
18.75
20.25
12
20
1.12
1.25
21.25
22.50
16
20
1.12
1.38
22.75
24.75
16
24
1.25
1.38
25.00
27.00
20
24
1.25
1.38
29.50
32.00
20
24
1.38
1.62
79
RF Gasket dimensions per ASME B16.21 for flanges ASME B16.5
Pressure Class 400, 600 and 900 psi - dimensions in inches
Nominal
Diameter
Outside Diameter
Inside
Diameter
400
600
900
1
/2
0.84
2.12
2.12
2.50
3
/4
1.06
2.62
2.62
2.75
1
1.31
2.88
2.88
3.12
1
1 /4
1.66
3.25
3.25
3.50
1
1 /2
1.91
3.75
3.75
3.88
2
2.38
4.38
4.38
5.62
1
2 /2
2.88
5.12
5.12
6.50
3
3.50
5.88
5.88
6.62
1
3 /2
4.00
6.38
6.38
-
4
4.50
7.00
7.62
8.12
5
5.56
8.38
9.50
9.75
6
6.62
9.75
10.50
11.38
8
8.62
12.00
12.62
14.12
10
10.75
14.12
15.75
17.12
12
12.75
16.50
18.00
19.62
14
14.00
19.00
19.38
20.50
16
16.00
21.12
22.25
22.62
18
18.00
23.38
24.12
25.12
20
20.00
25.50
26.88
27.50
24
24.00
30.25
31.12
33.00
80
Annex 4.5
FF Gasket dimensions per ASME B16.21 for flanges ASME B16.24
Cast Copper Alloy Flanges, Classes 150 and 300 psi - dimensions in inches
Pressure Class 150
Pressure Class 300
Nominal Inside
Bolt
Bolt Outside No. of Hole
Diameter Diam. Outside No. of Hole
Diameter Bolts Diam Circle Diameter Bolts Diam Circle
1
/2
0.84
3.50
4
0.62
2.38
3.75
4
0.62
2.62
3
/4
1.06
3.88
4
0.62
2.75
4.62
4
0.75
3.25
1
1.31
4.25
4
0.62
3.12
4.88
4
0.75
3.50
1
1 /4
1.66
4.62
4
0.62
3.50
5.25
4
0.75
3.88
1
1 /2
1.91
5.00
4
0.62
3.88
6.12
4
0.88
4.50
2
2.38
6.00
4
0.75
4.75
6.50
8
0.75
5.00
1
2 /2
2.88
7.00
4
0.75
5.50
7.50
8
0.88
5.88
3
3.50
7.50
4
0.75
6.00
8.25
8
0.88
6.62
1
3 /2
4.00
8.50
8
0.75
7.00
9.00
8
0.88
7.25
4
4.50
9.00
8
0.75
7.50
10.00
8
0.88
7.88
5
5.56
10.00
8
0.88
8.50
11.00
8
0.88
9.25
6
6.62
11.00
8
0.88
9.50
12.50
12
0.88
10.63
8
8.62
13.50
8
0.88
11.75
15.00
12
1.00
13.00
10
10.75
16.00
12
1.00
14.25
-
-
-
-
12
12.75
19.00
12
1.00
17.00
-
-
-
-
81
Annex 4.6
RF Gaskets per ASME B16.21 for flanges ASME B16.47 Series A
Classes 150, 300, 400 and 600 psi - Dimensions in inches
Nominal
Diameter
Outside Diameter
Inside
Diameter
150
300
400
600
22.00
26.00
27.75
27.63
28.88
26
26.00
30.50
32.88
32.75
34.12
28
28.00
32.75
35.38
35.12
36.00
30
30.00
34.75
37.50
37.25
38.25
32
32.00
37.00
39.62
39.50
40.25
34
34.00
39.00
41.62
41.50
42.25
36
36.00
41.25
44.00
44.00
44.50
38
38.00
43.75
41.50
42.26
43.50
40
40.00
45.75
43.88
44.58
45.50
42
42.00
48.00
45.88
46.38
48.00
44
44.00
50.25
48.00
48.50
50.00
46
46.00
52.25
50.12
50.75
52.26
48
48.00
54.50
52.12
53.00
54.75
50
50.00
56.50
54.25
55.25
57.00
52
52.00
58.75
56.25
57.26
59.00
54
54.00
61.00
58.75
59.75
61.25
56
56.00
63.25
60.75
61.75
63.50
58
58.00
65.50
62.75
63.75
65.50
60
60.00
67.50
64.75
66.25
67.75
22
(1)
NOTE: The 22” flange is for reference only. It does not belong to ASME B 16.47
82
Annex 4.7
RF Gaskets per ASME B16.21 for flanges ASME B16.47 Series B
Pressure Class 75, 150, 300, 400 and 600 psi - dimensions in inches
Nominal
Inside
Diameter Diameter
Outside Diameter
75
150
300
400
600
26
26.00
27.88
28.56
30.38
29.38
30.12
28
28.00
29.88
30.56
32.50
31.50
32.25
30
30.00
31.88
32.56
34.88
33.75
34.62
32
32.00
33.88
34.69
37.00
35.88
36.75
34
34.00
35.88
36.81
39.12
37.88
39.25
36
36.00
38.31
38.88
41.25
40.25
41.25
38
38.00
40.31
41.12
43.25
-
-
40
40.00
42.31
43.12
45.25
-
-
42
42.00
44.31
45.12
47.25
-
-
44
44.00
46.50
47.12
49.25
-
-
46
46.00
48.50
49.44
51.88
-
-
48
48.00
50.50
51.44
53.88
-
-
50
50.00
52.50
53.44
55.88
-
-
52
52.00
54.62
55.44
57.88
-
-
54
54.00
56.62
57.62
61.25
-
-
56
56.00
58.88
59.62
62.75
-
-
58
58.00
60.88
62.19
65.19
-
-
60
60.00
62.88
64.19
67.12
-
-
83
Annex 4.8
FF Gasket dimensions per ASME B16.21 for flanges MSS SP-51
Class 150LW - dimensions in inches
Nominal
Diameter
Inside
Diameter
Outside
Diameter
Number of
Bolts
Hole
Diameter
Bolt Circle
Diameter
1
/4
0.56
2.50
4
0.44
1.69
3
/8
0.69
2.50
4
0.44
1.69
1
/2
0.84
3.50
4
0.62
2.38
3
/4
1.06
3.88
4
0.62
2.75
1
1.31
4.25
4
0.62
3.12
1
1 /4
1.66
4.62
4
0.62
3.50
1
1 /2
1.91
5.00
4
0.62
3.88
2
2.38
6.00
4
0.75
4.75
1
2 /2
2.88
7.00
4
0.75
5.50
3
3.50
7.50
4
0.75
6.00
4
4.50
9.00
8
0.75
7.50
5
5.56
10.00
8
0.88
8.50
6
6.62
11.00
8
0.88
9.50
8
8.62
13.60
8
0.88
11.75
10
10.75
16.00
12
1.00
14.25
12
12.75
19.00
12
1.00
17.00
14
14.00
21.00
12
1.12
18.75
16
16.00
23.50
16
1.12
21.25
18
18.00
25.00
16
1.25
22.75
20
20.00
27.50
20
1.25
25.00
24
24.00
32.00
20
1.38
29.50
84
Annex 4.9
Gasket dimensions per ASME B16.21 for ASME B16.1
Class 25 Cast Iron Flanges - dimensions in inches
Juntas FF
RF gaskets
Nominal
Diameter
Inside
Diameter
4
4.50
6.88
9.00
8
0.75
7.50
5
5.56
7.88
10.00
8
0.75
8.50
6
6.62
8.88
11.00
8
0.75
9.50
Outside
Outside Number of
Hole
Diameter Diameter
Bolts
Diameter
Bolt
Circle
8
8.62
11.12
13.50
8
0.75
11.75
10
10.75
13.63
16.00
12
0.75
14.25
12
12.75
16.38
19.00
12
0.75
17.00
14
14.00
18.00
21.00
12
0.88
18.75
16
16.00
20.50
23.50
16
0.88
21.25
18
18.00
22.00
25.00
16
0.88
22.75
20
20.00
24.25
27.50
20
0.88
25.00
24
24.00
28.75
32.00
20
0.88
29.50
30
30.00
35.12
38.75
28
1.00
36.00
36
36.00
41.88
46.00
32
1.00
42.75
42
42.00
48.50
53.00
36
1.12
49.50
48
48.00
55.00
59.50
44
1.12
56.00
54
54.00
61.75
66.25
44
1.12
62.75
60
60.00
68.12
73.00
52
1.25
69.25
72
72.00
81.38
86.50
60
1.25
82.50
84
84.00
94.25
99.75
64
1.38
95.50
113.25
68
1.38
108.50
96
96.00
107.25
85
Annex 4.10
Gasket dimensions per ASME B16.21 for ASME B16.1
Class 125 Cast Iron Flanges - dimensions in inches
Juntas FF
RF gaskets
Nominal
Diameter
Inside
Diameter
1
1.31
2.62
4.25
4
0.62
3.12
1¼
1.66
3.00
4.62
4
0.62
3.50
1½
1.91
3.38
5.00
4
0.62
3.88
2
2.38
4.12
6.00
4
0.75
4.75
2½
2.88
4.88
7.00
4
0.75
5.50
3
3.50
5.38
7.50
4
0.75
6.00
3½
4.00
6.38
8.50
8
0.75
7.00
4
4.50
6.88
9.00
8
0.75
7.50
5
5.56
7.75
10.00
8
0.88
8.50
6
6.62
8.75
11.00
8
0.88
9.50
Outside
Outside Number of
Hole
Diameter Diameter
Bolts
Diameter
Bolt
Circle
8
8.62
11.00
13.50
8
0.88
11.75
10
10.75
13.38
16.00
12
1.00
14.25
12
12.75
16.12
19.00
12
1.00
17.00
14
14.00
17.75
21.00
12
1.12
18.75
16
16.00
20.25
23.50
16
1.12
21.25
18
18.00
21.62
25.00
16
1.25
22.75
20
20.00
23.88
27.50
20
1.25
25.00
24
24.00
28.25
32.00
20
1.38
29.50
30
30.00
34.75
38.75
28
1.38
36.00
36
36.00
41.25
46.00
32
1.62
42.75
42
42.00
48.00
53.00
36
1.62
49.50
48
48.00
54.50
59.50
44
1.62
56.00
86
Annex 4.11
RF Gasket dimensions per DIN 2690 – dimensions in mm
DN
4
6
8
10
15
20
25
32
40
50
65
80
100
125
150
175
200
250
300
350
400
450
500
600
700
800
900
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
Inside
Diameter
6
10
14
18
22
28
35
43
49
61
77
90
115
141
169
195
220
274
325
368
420
470
520
620
720
820
920
1020
1220
1420
1620
1820
2020
2220
2420
2620
2820
3020
3220
3420
3620
3820
4020
1 and 2.5
Use
Class
PN 6
1290
1490
1700
1900
2100
2305
2505
2705
2920
3120
3320
3520
3730
3930
4130
Outside Diameter – PN Class
16
10
25
6
30
28
33
38
43
53
Use Class PN 40
63
75
85
95
115
132
162
152
Use
192
182
Class
218
207
PN 16
248
237
255
273
262
285
328
330
318
342
378
385
373
402
438
445
423
458
490
497
473
515
540
557
528
565
595
618
578
625
695
735
680
730
810
805
785
830
915
910
890
940
1015
1010
990
1040
1120
1125
1090
1150
1340
1340
1305
1360
1545
1540
1520
1575
1770
1760
1720
1795
1970
1960
1930
2000
2180
2165
2135
2230
2380
2375
2345
2590
2585
2555
2790
2785
2760
3010
2970
3225
3170
3380
3590
3800
87
40
38
43
45
50
60
70
82
92
107
127
142
168
195
225
267
292
353
418
475
547
572
628
745
850
970
1080
1190
1395
1615
1830
-
88
CHAPTER
5
PTFE GASKETS
1. POLYTETRAFLUORETHYLENE (PTFE)
Polymer with exceptional chemical resistance, Polytetrafluorethylene – PTFE,
is the most widely used plastic for industrial sealing. The only products that chemically
attack PTFE are liquid alkaline metals and free fluorine.
Sintering or extruding PTFE, pure or mixed with other materials, obtains gasket
products, which are used in services where it is necessary to have a high chemical
resistance. There are materials with distinct physical properties to meet the needs of
each application. As with any fluid sealing material there is some overlapping between
each other. Several materials can be used successfully in the same application. The
most popular materials, with specific applications, characteristics and advantages are
discussed in the following paragraphs.
The PTFE also has excellent properties for electrical insulation, anti-stick,
impact resistance and low friction coefficient.
2. STYLES OF PTFE SHEETS
PTFE gaskets are used in services where it is necessary to have a high chemical
resistance. There are materials with distinct physical properties to meet the needs of
each application. As with any fluid sealing material there is some overlapping between
each other. Several materials can be used successfully in the same application. The
most popular materials, with specific applications, characteristics and advantages are
discussed in the following paragraphs.
89
2.1. MOLDED SINTERED PTFE SHEET
The Molded Sintered PTFE sheets were the first products introduced in the
market. They are manufactured from virgin or reprocessed PTFE resin, without fillers,
in a process of molding, compressing and sintering. As any plastic product the PTFE
exhibits a characteristic of creep when subjected a compression force. This
characteristic is very detrimental to the gasket performance since it requires frequent
retightening of the gasket to avoid or reduce leaks. This creep behavior is increased
with the temperature. The main advantages are the low cost, ample market availability
and high chemical resistance.
2.2. SKIVED PTFE SHEET
They are manufactured from virgin or reprocessed PTFE resin, without fillers,
in a process of skiving a sintered PTFE billet. This process was developed to overcome
manufacturing deficiencies of the Molded Process, however its products have the
same creep behavior problems.
2.3. MOLDED OR SKIVED FILLED PTFE SHEET
To reduce the creep behavior of Molded or Skived PTFE sheets mineral fillers
or fibers are added to reduce it. However, due to the manufacturing process (molding
or skiving) this reduction is not enough to produce a long-term effective seal.
2.4. RESTRUCTURED FILLED PTFE SHEET
To reduce the creep a new manufacturing process was developed to produce
Filled PTFE sheets. The material is subjected to a lamination before sintering, creating
a highly fibrillated structure. Creep at both room and high temperature is substantially
reduced. The first material in the market using this technology was the Gylon. To meet
the chemical service needs several mineral or artificial fillers are used, like Barite,
Mineral and Synthetic Silica, Barium Sulphate or Hollow Glass Micro-Spheres. Each
filler has an specific service application but there is a major overlapping of all of them
for normal applications. The most used fillers are:
• Barite: mineral used to produce sheets for strong caustic service. It is also
considered FDA compliant. It seems to be the most commonly used sheet,
it has a wide range of service applications including strong acids and
general chemical products.
• Mineral Silica: used to produce sheets for strong acidic service. Is also
used as a general service sheet since it has a broad range of applications
including mild caustic solutions.
• Hollow Glass Micro-Spheres: this filler produces a sheet with a high
compressibility for use with fragile or glass lined flanges replacing PTFE
envelope gaskets. It is not recommended for either strong hot caustic service.
90
• Synthetic Silica: it is used by some manufactures as a substitute for Glass
Micro-spheres since it yields sheets with compressibility closer to it.
2.5. EXPANDED PTFE
As an alternative to overcome the creep of PTFE is the hot expansion of it
before sintering. Gasket products expanded in one direction (cords or tapes) or biaxially (sheets) can be produced. Expanded PTFE has a high chemical resistance; it
also exhibit a very high compressibility and is ideal for use with fragile or glass lined
flanges. Most Expanded PTFE products in the market do not have fillers. Its main
drawback is the handling and installation of large gaskets or when it is not possible to
separate the flanges. It is often used as a replacement for the Hollow Glass MicroSpheres sheet.
3. TEALON® RESTRUCTURED FILLED PTFE SHEET
Tealon® gasket sheets were developed to meet the highest demands for PTFE
gaskets. Its lamination process before sintering creates a highly fibrillated structure,
which combined with a selected choice of fillers, results in a product with reduced
creep at both room and high temperature. To meet the chemical service needs the
fillers are: Barite, Mineral Silica and Hollow Glass Micro-Spheres.
TEALON® is a trademark of E.I. DuPont De Nemours and Company and is
used under license by Teadit.
3.1. TEADIT TEALON® STYLE 1570 SHEETS
Tealon® 1570 is produced with virgin Teflon resin filled with Hollow Glass
Micro-Spheres. The Table 5.1 shows the characteristics of Style 1570 Sheets.
Due to its filler carachteristics this product exhibits high compressibility and
is recommended for use in fragile or lined flanges, for service handling strong acids,
moderate caustic, chlorine dioxide, gases, solvents, water, steam, hydrocarbons and
chemical products. It is not recommended for strong and hot caustic media since it
can attack the Hollow Glass Micro-Spheres.
It is available in sheets 59" x 59" (1500 mm x 1500 mm), thickness range 1/16"
(1.6 mm) to 1/4" (6.4 mm), blue dyed.
3.2. TEADIT TEALON® STYLE 1580 SHEETS
Tealon® 1580 is produced with virgin PTFE resin filled with Barite. The Table
5.1 shows the characteristics of Style 1580 Sheets.
Due to its exceptional resistance it is recommended for strong and hot caustic
service, solvents, gases, water, steam, hydrocarbons and chemical products. It also
meets the requirements of the Food and Drug Administration (FDA) for use in food
91
and pharmaceutical applications. It has no dyes and can be used when contamination
is an issue.
It is available in sheets 59" x 59" (1500 mm x 1500 mm), thickness range 1/16"
(1.6 mm) to 1/4" (6.4 mm).
3.3. TEADIT TEALON® STYLE 1590 SHEETS
Tealon® 1590 is produced with virgin PTFE resin filled with Mineral Silica.
The Table 5.1 shows the characteristics of Style TF1590 Sheets.
Tealon® 1590 is General Service Sheet recommended for service handling strong
acids (except hydrofluoric), moderate caustic, gases, solvents, water, steam,
hydrocarbons and chemical products.
It is available in sheets 60" x 60" (1500 mm x 1600 mm), thickness range 1/16"
(1.5 mm) to 1/4" (6.4 mm), fawn dyed.
TEALON Style
Physical Chracteristics
o
Minimum Temperature
Maximum Temperature
Maximum Pressure
C
F
o
C
o
F
bar
psi
o
pH Range
Test Method
1570
1580
1590
-
-210
-350
260
500
55
800
-210
-350
260
500
83
1200
-210
-350
260
500
83
1200
0 - 14
0 - 14
12 000
8 600
350 000
250 000
4 - 10
0 - 14
12 000
8 600
350 000
250 000
7 - 12
40
14
2000
1.70
106
40
140
2000
2.90
181
140
2000
2.10
131
ASTM F 38
40
11
18
ASTM F 37 A
0.12
0.04
0.20
< 0.015
< 0.015
< 0.015
-
Compressibility, %
ASTM F 36 A
12 000
8 600
350 000
250 000
30-50
Recovery, %
ASTM F 36 A
30
1.5 mm thick
3 mm thick
o
psi x F 1/16" thick
1/8" mm thick
bar x oC
P x T Factor
Tensile Strenght
Specific Gravity
MPa
psi
g/cm3
lb/cu.ft
Creep Relaxation, %
Sealability, ml/hr ( .7 bar ) 1000 psi
Gas Permeability, cm3/min
ASTM Callout
-
ASTM 152
ASTM D 792
DIN 3535
ASTM
92
F456999A9B7 F451999A9 F451999A9B4
E99M6
E99M6
B2E99M6
3.4. TEALON® PERFORMANCE TESTS
3.4.1. HOT COMPRESSION TEST
Gaskets produced from Tealon® and from skived PTFE sheets were subjected
to a compression stress of 10 MPa (1500 psi) at 260o C (500o F) for 1 hour. The Figure
5.1 shows the test result. It can clearly be seen that the Tealon gasket has retained its
shape. Due to its high creep behavior the skived PTFE has lost its initial shape.
Figure 5.1
3.4.2. HOT CAUSTIC SODA IMMERSION
To verify the performance samples of Tealon were immersed in Caustic Soda,
33% concentration at 110ºC (230ºF), for 24 days. Figure 5.2 shows the weight change.
93
The 1580 Barite filled product showed the lowest change of the tested sheets.
The 1590 Silica filled sheet on the other hand showed severe weight loss. A visual
inspection of the samples after 24 days of immersion showed the Silica filled sheets
had some discoloration and pitting. The 1580 filled sheets showed no evidence of
chemical attack and for this reason is the recommended product for caustic media.
3.4.3. SULPHURIC ACID IMMERSION
To verify the performance in acidic services samples of Tealon® Restructured
Sheets were immersed in Sulfuric Acid, 20% concentration at 85o C (185o F), for 8 days.
Figure 5.3 shows the weight change.
Figure 5.3
Both 1580 Barite and 1590 Silica filled sheets had only a small weight increase
under these test conditions. A visual inspection of the samples showed no evidence
of chemical attack.
3.4..4. PRESSURE LOSS WITH THERMAL CYCLING
Gaskets made of Tealon® TF1570 and PTFE Skived Sheet were tested under
thermal cycling conditions.The objective of the test was to compare the pressure loss
(leak rate) of both gaskets. The Test Protocol used is as follows:
•
Install the gasket with a seating stress of 35 MPa (5000 psi).
94
•
•
•
•
•
•
•
•
•
Wait 30 minutes for the initial relaxation and increase the seating stress
again to 35 MPa (5000 psi).
Increase the temperature to 200º C (392º F).
Pressurize the Test Bench with 42 bar (600 psi). The gas inlet is then closed
for the remaining of the test.
The temperature is kept constant at 200º C (392º F) for 4 hours.
Turn the heating system off and let the Test Bench cool down.
When the temperature reaches 30º C (86º F) it is increased to 200º C (392º F).
The temperature is kept constant at 200º C (392º F) for 30 minutes.
This cycle is repeated 2 times.
The pressure, temperature and seating stress are recorded throughout the test.
The test results are shown in Figures 5.4 and 5.5.
Figure 5.4
Figure 5.5
95
This test is a good example of the difference between a skived sheet and
restructured PTFE sheets like Tealon®. As shown in Figure 5.5, the PTFE Skived Sheet
loses 44% of its initial seating stress as the gaskets thermocycle. This loss of seating
stress is the cause of the higher pressure loss for the PTFE Skived Sheet gasket as
shown in Figure 5.4 and is typical for this kind of product. Restructured PTFE products
like Tealon®, due to its fibrillated structure, have a better retention of the initial seating
stress and maintain a higher sealability.
3.4.5. HOT BLOW OUT TEST (HOBT-2)
To verfy the pressure resistance at elevated temperatures samples of Tealon®
were tested at the TTRL (Tigthness Testing and Research Laboratory of the University
of Montreal, Canada and by the CETIM (Centre de Industries Mechaniques), Nantes,
France. A summary of the test protocol known as HOBT-2 is as follows:
•
•
•
•
•
Flanges ASME B16.5 DN 3"- Class 150 psi.
Test Media: Helium.
Test Pressure: 435 psi.
Seating Stress: 5000 psi (34.5 MPa).
Test procedure: install gasket and pressurize the test bench. Increse the
temperature until the gasket blows out or it reaches 360º C (680º F).
Test results are as follows:
• TF1570:
• TF1580: reached 313º C (595º F)
• TF1590: the test reached its maximum temperature of 360º C (680º F) without
a gasket failure.
3.4.6. HOT GAS SERVICE
Tealon® gaskets have been approved by the DVGW – Deutscher Verein des
Gasund Wasserfaches e.V. (Germany) per DIN 3535 for hot gas service.
3.4.7. OXYGEN SERVICE
Tealon® 1580 has been approved by the Bundesansalt für Materialforschung
und –prüfung (BAM), Berlin, Germany, for Oxygen service in pressures up to 1200 psi
(83 bar) and 250o C (482o F).
3.4.8. TA-LUFT APPROVAL FOR REFINERY AND CHEMICAL SERVICE
Tealon® gaskets have been approved by the Staatliche Materialprüfungsanstalt –
Universität Stuttgart (MPA), Germany, according to the VDI 2440, for service in
Refineries, Petrochemical and Chemical plants. The maximum allowed leak rate is
10 -4 mbar-l/(s-m). The test results are shown in Table 5.2:
96
Table 5.2
Tealon® TA-Luft Test Results
Style
Leak Rate - mbar·l/(s·m)
1570
3.7·10-6
1580
5.9·10-7
1590
1.1·10-6
3.5. TEALON® CHEMICAL COMPATIBILITY
Annex 5.1 shows the Chemical Compatibility of the Tealon® sheets with several
chemical products.
3.6. BOLTING CALCULATIONS
The Contants for ASME calculations for (1/16") 1.5 mm gasket thickness are
shown in Table 5.3.
Table 5.3
ASME Gasket Constants
Style
m
y - psi
Gb - MPa
a
Gs - MPa
Maximum Gasket
Stress – MPa (psi)
1570
2
1500
244
0.31
1.28 x 10-2
1580
2
1800
114
0.447
1.6 x 10-3
1590
4.4
2500
260
0.351
6.3
276 (40 000)
276 (40 000)
276 (40 000)
4. EXPANDED PTFE
The exceptional properties which distinguish the expanded PTFE products
are the result of a special stretching process which produces a highly fibrilated
microstructure with millions of fibrils connected with each other. This gives the material
its unique strength and pressure resistance, without the cold flow and creep
characteristics of the sintered PTFE.
97
Expanded PTFE Products have outstanding plastic malleability and flexibility;
they conform easily to irregular and rough surfaces. At the same time they withstand
high flange loads and high internal pressures.
4.1. SERVICE CHARACTERISTICS
The most important service characteristics are as follows:
• Pure PTFE without fillers or additives for better chemical resistance, pH
ranges from 0 to 14. Not recommended for molten alkali and elemental fluorine)
• Temperature range 400o F (–240o C) to 500o F (+270o C), for continuous
service and up to 590o F (310o C) for short periods.
• Pressure range from full vacuum to 2900 psi (200 bar).
• Low creep not requiring frequent retightening of bolts like sintered PTFE.
• High compressibility recommended for fragile flange materials like ceramic,
glass or plastic.
• Conforms easily to irregular and rough surfaces. .
• Physiologically harmless up to 500o F (+270o C). It has no smell and is
tasteless.
• It is non-toxic and does not contaminate.
• Microorganisms or fungi do not influence it.
• Approved by the FDA (Food and Drug Administration – USA) for use with
foods and drugs.
• It contains no extractable substances.
• Unlimited shelf life, it is non-aging.
• Atmospheric agents like sunlight, ozone and ultraviolet light (UV) do not
attack it.
4.2. APPROVALS
Teadit Expanded PTFE products have been approved by several international
organizations for use with gas, potable water, foods and oxygen:
• BAM Tgb. No. 6228/89 4-2346: for use in steel, copper and copper alloys
flat faced or tongue and groove flanges, in oxygen service in pressures up
to 1500 psi (100 bar) and 195o F (90o C).
• DVGW Reg. No. G88e089: for gas line service with pressures up to 240 psi
(16 bar) and temperatures from 14o F (–10o C) up to 120o F (+50o C).
• FMPA Reg. No. V/91 2242 Gör/Gö: for food products service.
• British Oxygen Corporation (BOC) Reg. No. 1592 4188/92: for use in gaseous
and liquid oxygen service.
• British Water Research Council (WRC) Reg. No. MVK/9012502: for cold
and hot potable water service.
• TA-Luft: Teadit 24SH sheets have been approved by the Staatliche
Materialprüfungsanstalt – Universität Stuttgart (MPA), Germany, according
to the VDI 2440, for service in Refineries, Petrochemical and Chemical plants.
The leak rate was: 2.6·10-7 mbar·l/(s·m).
98
4.3. TEADIT STYLE 24B JOINT SEALANT
The most common form of Expanded PTFE is a tape with an adhesive strip on
one side. This tape is placed over the sealing surface of one of the flanges. The
adhesive strip backing makes the installation very easy as shown in Figure 5.6, even
for irregular shaped flanges.
After seating, Expanded PTFE gaskets are reduced to a very thin cross section
with high tensile strength. This very thin cross section reduces the gasket tendency
to blowout increasing its pressure resistance.
Figure 5.6
For standard size flanges the size recommendations are in Table 5.4. For nonstandard flanges the recommended width is 1/3 to 1/2 of the flange sealing surface.
For flanges with scratches, tool marks and other irregularities choose the thickest
possible size.
Table 5.4
Size Recommendations
Flange Nominal Diameter - in
Up to 1/2
¾ to 1 1/2
2 to 4
5 to 8
10 to 16
18 to 24
24 to 36
36 and up
Style 24B size - in
1/8
3/16
1/4
3/8
1/2
5/8
3/4
1
99
4.4. EXPANDED PTFE TAPES 24BB AND SHEETS 24 SH
Sheets and tapes are manufactured by expanding virgin PTFE using a
proprietary process that produces a uniform and highly fibrilated microstructure with
equal tensile strength in all directions. The resulting product exhibits characteristics
significantly different than conventional PTFE. It is softer and more flexible, conforming
easily to irregular and rough surfaces. It is also easier to compress and has a reduced
cold flow and creep. It is ideally suited to cut or punch gaskets, for flanges with a
narrow sealing area or where a defined gasket width after seating is needed.
Tapes are supplied with or without a self-adhesive backing strip to facilitate
easy installation.
Table 5.5
24 BB Tape Standard Sizes – feet per roll
Thickness
in
1/64
1/32
1/16
1/8
1/2
100
50
25
25
3/4
100
50
25
25
1
100
50
25
25
Width - in
2
100
50
25
25
4
NA
50
25
25
6
NA
50
25
25
8
NA
50
25
25
Available 24 SH sheet size is 60" x 60" (1500 mm x 1500 mm), thickness 1/32"
(0.8 mm), 1/16" (1.6 mm), 3/32" (2.4 mm), 1/8" (3.2 mm), 3/16" (4.8 mm) and 1/4" (6.4 mm).
4.5. GASKET PARAMETERS
The parameters for gasket design are shown in Table 5.6.
Table 5.6
Gasket Constants
Characteristic
m
y (psi)
Gb (MPa)
a
Gs (psi)
Maximum Seating Stress (MPa)
24 B Joint Sealant
2
2 800
8.786
0.193
1.862 E-14
150
100
24 SH Sheet
2
2 800
2.945
0.313
2.621 E-5
150
24BB Tape
2
2 800
2.945
0.313
2.621 E-5
150
The Figure 5.7 shows the minimum seating stress to achieve a level of
sealability of 0.01 mg/sec-m with Nitrogen. Higher seating pressures than indicated
reduce the leakage to less than 0.01 mg per second per meter of gasket length.
Figure 5.7
4.6. CHEMICAL COMPATIBILITY
The Annex 5.1 shows the chemical compatibility of Teadit Expanded PTFE
with several chemical products.
5. SINTERED PTFE SHEETS
Teadit has available three basic styles of Sintered PTFE sheets: virgin,
mechanical grade and glass reinforced.
5.1. VIRGIN PTFE STYLE 1500 SHEET
The Teadit Style 1500 Virgin PTFE Sheets are manufactured from Virgin PTFE
polymer. They are particularly recommended for applications in the food and beverage
industry where high purity materials are required. It is also used where contamination
or discoloration of flow media cannot be tolerated.
Thicknesses are 1/64", 1/32", 1/16", 3/32", 1/8", 3/16", 1/4". Sheet sizes are
48" x 48", 60" x 60" and 48" or 60" wide continuous rolls.
101
5.2. GLASS FILLED PTFE STYLE 1525 SHEET
The Teadit Style 1525 PTFE Sheets are filled with 25% Glass Fibers by weight.
The filled material significantly reduces cold flow and creep and increases wear
resistance compared to unfilled PTFE sheet. Style 1525 can handle a very broad range
of chemicals with the exception of molten alkali metals and elemental fluorine.
5.3. MECHANICAL GRADE PTFE STYLE 1550 SHEET
The Teadit Style 1550 Mechanical Grade PTFE Sheets are particularly
recommended for applications in the industrial process industries where high purity
materials are not required. It is more economical than virgin PTFE sheet.
Thicknesses are 1/64", 1/32", 1/16", 3/32", 1/8", 3/16", 1/4". Sheet sizes are
48" x 48", 60" x 60" and 48" or 60" wide continuous rolls.
Thicknesses are 1/64", 1/32", 1/16", 3/32", 1/8", 3/16", 1/4". Sheet sizes are
48" x 48" or 48" wide continuous rolls.
6. PTFE ENVELOPE GASKETS
PTFE Envelope gaskets are manufactured from a Compressed Sheet gasket
core with a PTFE protection cover. They combine the mechanical strength, resilience
and bolt load retention of Compressed Gasket Sheet with the chemical resistance of
PTFE. They are used in equipment with glass; ceramic or glass coated steel flanges.
Maximum service temperature is 500ºF (260ºC), the limit for PTFE. A Beater Addition or
Rubber core can also be used.
6.1. STYLE 933-V
It is the most common and economical style (Figure 5.8). Its total thickness is
limited to approximately 1/8 in (3.2 mm). Due to the high cost of PTFE the envelope is
normally manufactured in raised face dimensions. In some applications to help the
assembly of the gasket the sheet core can be made with the same drilling as the flange.
102
Figure 5.8
6.2. TYLE 933-U
When a gasket capable of absorbing more irregularities or with higher resiliency
corrugated stainless steel core is added to the core as shown in Figure 5.9.
Figure 5.9
103
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Abietic Acid
Acetaldehyde
Acetamide
Acetic Acid (Crude,Glacial,Pure)
Acetic Anhydride
Acetone
Acetonitrile
Acetophenone
2-Acetylaminofluorene
Acetylene
Acrolein
Acrylamide
Acrylic Acid
Acrylic Anhydride
Acrylonitrile
Air
Allyl Acetate
Allyl Chloride
Allyl Methacrylate
Aluminum Chloride
Aluminum Fluoride
Aluminum Hydroxide (Solid)
Aluminum Nitrate
Aluminum Sulfate
Alums
4-Aminodiphenyl
Ammonia, Liquid or Gas
Ammonium Chloride
Ammonium Hydroxide
Ammonium Nitrate
Ammonium Phosphate, Monobasic
Ammonium Phosphate, Dibasic
Ammonium Phosphate, Tribasic
Ammonium Sulfate
TF1570
A
A
A
A
A
A
A
A
A
A
B
B
B
A
B
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
104
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
B
B
B
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
B
B
B
A
B
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Amyl Acetate
Amyl Alcohol
Aniline, Aniline Oil
Aniline Dyes
o-Anisidine
Aqua Regia
Aroclors
Asphalt
Aviation Gasoline
Barium Chloride
Barium Hydroxide
Barium Sulfide
Baygon
Beer
Benzaldehyde
Benzene, Benzol
Benzidine
Benzoic Acid
Benzonitrile
Benzotrichloride
Benzoyl Chloride
Benzyl Alcohol
Benzyl Chloride
Biphenyl
Bis(2-chloroethyl)ether
Bis(chloromethyl)ether
Bis(2-ethylhexyl)phthalate
Black Sulfate Liquor
Blast Furnace Gas
Bleach (Sodium Hyprochlorite)
Boiler Feed Water
Bórax
Boric Acid
Brine (Sodium Chloride)
TF1570
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
* See note at the end of the table
105
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Bromine
Bromine Trifluoride
Bromoform
Bromomethane
Butadiene
Butane
2-Butanone
Butyl Acetate
Butyl Alcohol,Butanol
n-Butyl Amine
tert-Butyl Amine
Butyl Methacrylate
Butyric Acid
Calcium Bisulfite
Calcium Chloride
Calcium Cyanamide
Calcium Hydroxide
Calcium Hypochlorite
Calcium Nitrate
Calflo AF
Calflo FG
Calflo HTF
Calflo LT
Cane Sugar Liquors
Caprolactam
Captan
Carbaryl
Carbolic Acid,Phenol
Carbon Dioxide,Dry or Wet
Carbon Disulfide
Carbon Monoxide
Carbon Tetrachloride
Carbonic Acid
Carbonyl Sulfide
TF1570
A
C
A
A
B
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
106
C: not recommended
TF1580
A
C
A
A
B
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
C
A
A
B
A
A
A
A
A
A
B
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Castor Oil
Catechol
Cetane (Hexadecane)
China Wood Oil
Chloramben
Chlorazotic Acid (Aqua Regia)
Chlordane
Chlorinated Solvents,Dry or Wet
Chlorine, Dry or Wet
Chlorine Dioxide
Chlorine Trifluoride
Chloroacetic Acid
2-Chloroacetophenone
Chloroazotic Acid (Aqua Regia)
Chlorobenzene
Chlorobenzilate
Chloroethane
Chloroethylene
Chloroform
Chloromethyl Methyl Ether
Chloronitrous Acid (Aqua Regia)
Chloroprene
Chlorosulfonic Acid
Chrome Plating Solutions
Chromic Acid
Chromic Anhydride
Chromium Trioxide
Citric Acid
Coke Oven Gas
Copper Chloride
Copper Sulfate
Corn Oil
Cotton Seed Oil
Creosote
TF1570
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
107
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Cresols, Cresylic Acid
Crotonic Acid
Crude Oil
Cumene
Cyclohexane
Cyclohexanone
2,4-D, Salts and Esters
Detergent Solutions
Diazomethane
Dibenzofuran
Dibenzylether
1,2-Dibromo-3-chloropropane
Dibromoethane
Dibutyl Phthalate
Dibutyl Sebacate
o-Dichlorobenzene
1,4-Dichlorobenzene
3,3-Dichlorobenzidene
Dichloroethane (1,1 or 1,2)
1,1-Dichloroethylene
Dichloroethyl Ether
Dichloromethane
1,2-Dichloropropane
1,3-Dichloropropene
Dichlorvos
Diesel Oil
Diethanolamine
N,N-Diethylaniline
Diethyl Carbonate
Diethyl Sulfate
3,3-Dimethoxybenzidene
Dimethylaminoazobenzene
N,N-Dimethyl Aniline
3,3-Dimethylbenzidine
TF1570
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
108
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
TF1570
Product
Dimethyl Carbamoyl Chloride
A
Dimethyl Ether
A
Dimethylformamide
A
Dimethyl Hydrazine, Unsymmetrical
A
Dimethyl Phthalate
A
Dimethyl Sulfate
A
4,6-Dinitro-o-Cresol and Salts
A
2,4-Dinitrophenol
A
2,4-Dinitrotoluene
A
Dioxane
A
1,2-Diphenylhydrazine
A
Diphyl DT
A
Dowfrost
A
Dowfrost HD
A
Dowtherm 4000
A
Dowtherm A
A
Dowtherm E
A
Dowtherm G
A
Dowtherm HT
A
Dowtherm J
A
Dowtherm Q
A
Dowtherm SR-1
A
Epichlorohydrin
A
1,2-Epoxybutane
A
Ethane
A
Ethers
A
Ethyl Acetate
A
Ethyl Acrylate
B
Ethyl Alcohol
A
Ethylbenzene
A
Ethyl Carbamate
A
Ethyl Cellulose
A
Ethyl Chloride
A
Ethyl Ether
A
* See note at the end of the table
109
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Ethyl Hexoate
Ethylene
Ethylene Bromide
Ethylene Dibromide
Ethylene Dichloride
Ethylene Glycol
Ethyleneimine
Ethylene Oxide
Ethylene Thiourea
Ethylidine Chloride
Ferric Chloride
Ferric Phosphate
Ferric Sulfate
Fluorine, Gas
Fluorine, Liquid
Fluorine Dioxide
Formaldehyde
Formic Acid
Fuel Oil
Fuel Oil, Acid
Furfural
Gasoline, Refined
Sour
Gelatin
Glucose
Glue, Protein Base
Glycerine, Glycerol
Glycol
Grain Alcohol
Grease, Petroleum Base
Green Sulfate Liquor
Heptachlor
Heptane
Hexachlorobenzene
TF1570
A
A
A
A
A
A
B
B
A
A
A
A
A
C
C
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
* See note at the end of the table
110
C: not recommended
TF1580
A
A
A
A
A
A
A
B
A
A
A
A
A
C
C
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
B
B
A
A
A
A
A
C
C
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
C
C
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Hexachlorobutadiene
Hexachlorocyclopentadiene
Hexachloroethane
Hexadecane
Hexamethylene Diisocyanate
Hexamethylphosphoramide
Hexane
Hexone
Hydraulic Oil, Mineral
Synthetic
Hydrazine
Hydrobromic Acid
Hydrochloric Acid
Hydrocyanic Acid
Hydrofluoric Acid, Anhydrous
Hydrofluorosilicic Acid
Hydrofluosilicic Acid
Hydrogen
Hydrogen Bromide
Hydrogen Fluoride
Hydrogen Peroxide,10-90%
Hydrogen Sulfide,Dry or Wet
Hydroquinone
Iodine Pentafluoride
Iodomethane
Isobutane
Isooctane
Isophorone
Isopropyl Alcohol
Jet Fuels (JP Types)
Kerosene
Lacquer Solvents
Lacquers
TF1570
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
C
C
A
A
C
A
A
A
B
A
A
A
A
A
A
A
A
A
* See note at the end of the table
111
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
C
A
A
A
B
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
C
C
A
A
C
A
A
A
B
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Lactic Acid, 150°F and below
Above 150°F
Lime Saltpeter (Calcium Nitrates)
Lindane
Linseed Oil
Lithium Bromide
Lithium, Elemental
Lubricating Oils,Mineral or Petroleum Types
Lubricating Oils, Refined
Lubricating Oils, Sour
Lye
Magnesium Chloride
Magnesium Hydroxide
Magnesium Sulfate
Maleic Acid
Maleic Anhydride
Mercuric Chloride
Mercury
Methane
Methanol, Methyl Alcohol
Methoxychlor
Methylacrylic Acid
Methyl Alcohol
2-Methylaziridine
Methyl Bromide
Methyl Chloride
Methyl Chloroform
4,4 Methylene Bis (2-chloroaniline)
Methylene Chloride
4,4-Methylene Dianiline
Methylene Diphenyldiisocyanate
Methyl Ethyl Ketone
Methyl Hydrazine
TF1570
A
A
A
A
A
A
C
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
* See note at the end of the table
112
C: not recommended
TF1580
A
A
A
A
A
A
C
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
C
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Methyl Iodide
Methyl Isobutyl Ketone (MIBK)
Methyl Isocyanate
Methyl Methacrylate
N-Methyl-2-Pyrrolidone
Methyl Tert.Butyl Ether (MTBE)
Milk
Mineral Oils
Mobiltherm 600
Mobiltherm 603
Mobiltherm 605
Mobiltherm Light
Molten Alkali Metals
Monomethylamine
MultiTherm 100
MultiTherm 503
MultiTherm IG-2
MultiTherm PG-1
Muriatic Acid
Naphtha
Naphthalene
Naphthols
Natural Gas
Nickel Chloride
Nickel Sulfate
Nitric Acid, Less than 30%
Above 0,3
Crude
Red Fuming
Nitrobenzene
4-Nitrobiphenyl
2-Nitro-Butanol
Nitrocalcite (Calcium Nitrate)
Nitrogen
TF1570
A
A
A
B
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
113
C: not recommended
TF1580
A
A
A
B
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
B
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Nitrogen Tetroxide
Nitrohydrochloric Acid (Aqua Regia)
Nitromethane
2-Nitro-2-Methyl Propanol
Nitromuriatic Acid (Aqua Regia)
4-Nitrophenol
2-Nitropropane
N-Nitrosodimethylamine
N-Nitroso-N-Methylurea
N-Nitrosomorpholine
Norge Niter (Calcium Nitrate)
Norwegian Saltpeter (Calcium Nitrate)
N-Octadecyl Alcohol
Octane
Oil, Petroleum
Oils, Animal and Vegetable
Oleic Acid
Oleum
Orthodichlorobenzene
Oxalic Acid
Oxygen, Gas
Ozone
Palmitic Acid
Paraffin
Paratherm HE
Paratherm NF
Parathion
Paraxylene
Pentachloronitrobenzene
Pentachlorophenol
Pentane
Perchloric Acid
Perchloroethylene
Petroleum Oils,Crude
Refined
TF1570
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
114
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Phenol
p-Phenylenediamine
Phosgene
Phosphate Esters
Phosphine
Phosphoric Acid,Crude
Pure, < 45%
Pure, > 45%, >150°F
Pure, > 45%, > 150°F
Phosphorus, Elemental
Phosphorus Pentachloride
Phthalic Acid
Phthalic Anhydride
Picric Acid, Molten
Picric Acid, Water Solution
Pinene
Piperidine
Polyacrylonitrile
Polychlorinated Biphenyls
Potash, Potassium Carbonate
Potassium Acetate
Potassium Bichromate
Potassium Chromate, Red
Potassium Cyanide
Potassium Dichromate
Potassium, Elemental
Potassium Hydroxide
Potassium Nitrate
Potassium Permanganate
Potassium Sulfate
Producer Gas
Propane
1,3-Propane Sultone
Beta-Propiolactone
TF1570
A
A
A
A
A
C
A
B
B
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
C
B
A
A
A
A
A
A
A
* See note at the end of the table
115
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
C
B
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
C
A
B
C
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
C
C
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Propionaldehyde
Propoxur (Baygon)
Propyl Nitrate
Propylene
Propylene Dichloride
Propylene Oxide
1,2-Propylenimine
Prussic Acid, Hydrocyanic Acid
Pyridine
Quinoline
Quinone
Refrigerant type 10
11
12
13
13B1
21
22
23
31
32
112
113
Refrigerant type 114
114B2
115
123
124
125
134a
141b
142b
143a
152a
TF1570
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
116
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
TF1570
Product
Refrigerant type 218
A
290
A
500
A
502
A
503
A
C316
A
C318
A
HP62
A
HP80
A
HP81
A
Salt Water
A
Saltpeter, Potassium Nitrate
A
2,4-D Salts and Esters
A
Sewage
A
Silver Nitrate
A
Skydrols
A
Soap Solutions
A
Soda Ash, Sodium Carbonate
A
Sodium Bicarbonate, Baking Soda
A
Sodium Bisulfate, Dry
A
Sodium Bisulfite
A
Sodium Chlorate
A
Sodium Chloride
A
Sodium Cyanide
C
Sodium, Elemental
C
Sodium Hydroxide
B
Sodium Hypochlorite
A
Sodium Metaborate Peroxyhydrate
A
Sodium Metaphosphate
A
Sodium Nitrate
A
Sodium Perborate
A
Sodium Peroxide
A
Sodium Phosphate, Monobasic
A
Sodium Phosphate, Dibasic
B
* See note at the end of the table
117
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
C
C
A
A
B
A
A
A
A
B
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Sodium Phosphate, Tribasic
Sodium Silicate
Sodium Sulfate
Sodium Sulfide
Sodium Superoxide
Sodium Thiosulfate, Hypo
Soybean Oil10
Stannic Chloride
Steam
Stearic Acid
Stoddard Solvent
Styrene
Styrene Oxide
Sulfur Chloride
Sulfur Dioxide
Sulfur, Molten
Sulfur Trioxide, Dry or Wet
Sulfuric Acid, 10%, 150°F and below
10%, Above 150°F
10-75%, 500°F and below
75-98%, 150°F and below
75-98%, 150°F to 500°F
Sulfuric Acid, Fuming
Sulfurous Acid
Syltherm 800
Syltherm XLT
Tannic Acid
Tar
Tartaric Acid
2,3,7,8-TCDB-p-Dioxin
Tertiary ButylAmine
Tetrabromoethane
Tetrachlorethane
Tetrachloroethylene
TF1570
B
B
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
B
B
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
118
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
B
B
C
A
A
A
A
A
A
A
A
A
A
A
TF1590
C
B
A
A
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
Product
Tetrahydrofuran, THF
Therminol 44
Therminol 55
Therminol 59
Therminol 60
Therminol 66
Therminol 75
Therminol D12
Therminol LT
Therminol VP-1
Therminol XP
Thionyl Chloride
Titanium Sulfate
Titanium Tetrachloride
Toluene
2,4-Toluenediamine
2,4-Toluenediisocyanate
Toluene Sulfonic Acid
o-Toluidine
Toxaphine
Transformer Oil (Mineral Type)
Transmission Fluid A
Trichloroacetic Acid
1,2,4- Trichlorobenzene
1,1,2-Trichloroethane
Trichloroethylene
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
Tricresylphosphate
Triethanolamine
Triethyl Aluminum
Triethylamine
Trifluralin
2,2,4-Trimethylpentane
TF1570
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
* See note at the end of the table
119
C: not recommended
TF1580
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Annex 5.1
Tealon Chemical Compatibility Chart*
A: recommended
B: consult with Teadit
TF1570
Product
Tung Oil
A
Turpentine
A
UCON Heat Transfer Fluid 500
A
UCON Process Fluid WS
A
Varnish
A
Vinegar10
A
Vinyl Acetate
B
Vinyl Bromide
B
Vinyl Chloride
B
Vinylidene Chloride
B
Vinyl Methacrylate
A
Water, Acid Mine, with Oxidizing Salt
A
No Oxidizing Salts
A
Water, Distilled
A
Water, Distilled Return Condensate
A
Water, Distilled Seawater
A
Water, Distilled Tap
A
Whiskey and Wines
A
Wood Alcohol
A
Xceltherm 550
A
Xceltherm 600
A
Xceltherm MK1
A
Xceltyherm XT
A
Xylene
A
Zinc Chloride
A
Zinc Sulfate
A
C: not recommended
TF1580
A
A
A
A
A
A
B
B
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TF1590
A
A
A
A
A
A
B
B
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
SH/24BB
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
NOTE: Properties and application parameters shown throughout this Tealon Chemical
Compatibility Chart are typical. Your specific application should not be undertaken
without independent study and evaluation for suitability. For specific application
recommendations consult with TEADIT. Failure to select proper sealing products
could result in property damage and/or serious personal injury. Specifications
subject to change without notice; this edition cancels all previous issues.
120
CHAPTER
6
MATERIALS FOR
METALLIC GASKETS
1. CORROSION
On specifying the material for a metallic gasket, we must analyze the metal or
alloy properties and its reactions under stress and temperature. Special attention
must be given to:
• Stress Corrosion: stainless steel 18-8 can show stress corrosion in the
presence of certain fluids. The Annex 6.1 shows products that can cause
stress corrosion in the most frequently used alloys for industrial gaskets.
• Intergranular Corrosion: some chemical products can precipitate carbides
in austenitic stainless steel in temperatures between 790o F (420 o C) and
1490o F (810o C). This precipitation is known as Intergranular Corrosion.
The Annex 6.2 shows products, which induce Intergranular Corrosion.
• Fluid Compatibility: the gasket should resist deterioration or corrosive
action by the sealed product and at the same time avoid its
contamination. Annex 6.3 presents recommendations for most frequently
used metallic gasket materials.
Following are the most widely used alloys in manufacturing industrial gaskets,
their major characteristics, temperature limits and approximate Brinell hardness (HB).
2. CARBON STEEL
Material frequently used in manufacturing jacketed gaskets and Ring Joints.
Due to its low resistance to corrosion it should not be used in water, diluted acids or
121
saline solutions. It may be used in alkalis and concentrated acids. Temperature limit:
900o F (500o C). Hardness: 90 to 120 HB.
3. STAINLESS STEEL AISI 304
Alloy with 18% Cr and 8% Ni is the material most used in the manufacturing
of industrial gaskets due to its excellent resistance to corrosion, low cost and
availability in the market. Its maximum operating temperature is 1400o F (760o C). Due to
Stress and Intergranular Corrosion, its continuous service temperature is limited to
790o F (420o C). Hardness: 160 HB.
4. STAINLESS STEEL AISI 304L
It has the same resistance to corrosion as the AISI 304. Since its Carbon
content is limited to 0.03%, it has less Intergranular Carbon precipitation and therefore
less Intergranular Corrosion. Its operational limit for continuous service is 1400o F
(760o C). It is susceptible to Stress Corrosion. Hardness: 160 HB.
5. STAINLESS STEEL AISI 316
This alloy with 18% Ni, 13% Cr and 2% Mo, offers excellent resistance to
corrosion. It can have carbonate precipitation at temperatures between 860o F (460o C)
and 1650o F (900o C), under severe corrosion conditions. Maximum recommended
temperature for continuous service is 1400o F (760o C). Hardness: 160 HB.
6. STAINLESS STEEL AISI 316L
It has the same chemical composition as the AISI 316 but its Carbon content
is limited to 0.03%, which inhibits the Intergranular Carbon precipitation and
consequently, the Intergranular Corrosion. The maximum service temperature is 1400o
F (760o C). Hardness: 160 HB.
7. STAINLESS STEEL AISI 321
Austenitic stainless steel alloy with 18% Cr and 10% Ni stabilized with Ti,
which reduces the Intergranular Carbon precipitation and also the Intergranular
Corrosion. It can be used in temperatures up to 1500o F (815o C). Hardness: 160 HB.
8. STAINLESS STEEL AISI 347
Alloy similar to the AISI 304 stabilized with Cb and Ta to reduce carbonate
precipitation and Intergranular Corrosion. It is subject to Stress Corrosion. Has good
performance in high temperature corrosive service. Maximum temperature: 1550o F
(815o C). Hardness: 160 HB.
122
9. MONEL
Alloy with 67% Ni and 30% Cu, it offers excellent resistance to the majority of
acids and alkalis, except to extremely oxidant acids. Subject to stress corrosion and
therefore should not be used in the presence of fluorine-silicon acid and Mercury. In
combination with PTFE, it is used frequently in Spiral Wound gaskets for severe
corrosion services. Operating maximum temperature: 1500o F (815o C). Hardness: 95 HB.
10. NICKEL 200
Alloy with 99% Ni, offers great resistance to caustic solutions, even thought
it does not have the same global resistance of the Monel. It is also used in Spiral
Wound and jacketed gaskets for special applications. Maximum operating temperature:
1400o F (760o C). Hardness: 110 HB.
11. COPPER
Material often used in small dimension gaskets, where the maximum seating
stress is limited. Maximum operating temperature: 500o F (260o C). Hardness: 80 HB.
12. ALUMINUM
Due to its excellent resistance to corrosion and easy handling it is very often
used in manufacturing gaskets. Maximum service temperature: 860o F (460o C). Hardness:
35 HB.
13. INCONEL
Alloy with 70% Ni, 15% Cr and 7% Fe, it has excellent corrosion resistance
from cryogenic to high temperatures. Temperature limit: 2000o F (1100o C). Hardness:
150 HB.
14. TITANIUM
Metal with excellent corrosion properties in elevated temperatures, oxidant
service, Nitric acid and caustic solutions. Temperature limit: 2000 o F (1100 o C).
Hardness: 215 HB.
Besides these materials the most commonly used in industrial applications
are the ones sometimes recommended as Hastelloy, Carpenter and others, depending
on the operational circumstances. They are not analyzed in this book due the fact that
their application is restricted to very special situations when the use of an alternative
material is not possible.
123
ANNEX 6.1
STRESS CORROSION CHART*
A: Aluminum
B: Brass
C: Carbon Steel
M: Monel
S: Stainless Steel 18-8
N: Nickel
C
X
SERVICE
Ammonium Chloride
Ammonia - diluted
Ammonia – pure
Ammonium Nitrate
Butane + Sulfur Dioxide
Calcium Bromide
Chloridic Acid
Chromic Acid
Cresylic Acid vapor
Cyanogen
Fluorsilisic Acid
Hydrochloric Acid
Hydrogen Chloride + water
Hydrogen Cyanide + water
Hydrogen Sulfide + water
Hydrofluoric Acid
Inorganic Chlorides + water
Inorganic Nitrates
Mercurous Nitrate
Mercury
Nitric Acid diluted
Nitric Acid vapor
Nitric Acid + Magnesium Chloride
Oleum
Organic Chlorides + water
Pickling Acids
Potassium Hydroxide
Potassium Permanganate
Salt water + Oxygen
Silicofluoride Salts
Sodium Hydroxide
Steam
Sulfate Liquor (white)
Sulfide Liquor
Sulfuric Acid + Nitric Acid
Sulfur Compounds
S
B
M
N
A
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
124
ANNEX 6.2
PRODUCTS THAT CAN INDUCE INTERGRANULAR CORROSION IN
AUSTENIC STAINLESS STEELS
PRODUCT
Acetic Acid
Acetic Acid + Salicylic Acid
Ammonium Nitrate
Ammonium Sulfate
Ammonium Sulfate + Sulfuric Acid
Beet Juice
Cyanidric Acid
Cyanidric Acid + Sulfur Dioxide
Calcium Nitrate
Chromic Acid
Chromium Chloride
Copper Sulfate
Crude Oil
Fatty Acids
Ferric Chloride
Ferric Sulfate
Formic Acid
Hydrocyanic Acid
Hydrocyanic Acid + Sulfur Dioxide
Hydrocyanic Acid + Hydrofluoric Acid
Lactic Acid
Lactic Acid + Nitric Acid
Maleic Acid
Nitric Acid + Hydrochloric Acid
Nitric Acid + Hydrofluoric Acid
Oxalic Acid
Phenol + Naphthenic Acid
Phosphoric Acid
Phthalic Acid
Salt spray
Sea Water
Silver Nitrate + Acetic Acid
Sodium Bisulfate
Sodium Hydroxide + Sodium Sulfide
Sodium Hypochlorite
Sulfide Cooking Liquor
Sulfide Digester Acid
125
ANNEX 6.2 (Continued)
PRODUCTS THAT CAN INDUCE INTERGRANULAR CORROSION IN
AUSTENIC STAINLESS STEELS
PRODUCT
Sulfamic Acid
Sulfur Dioxide + water
Sulfuric Acid
Sulfuric Acid + Acetic Acid
Sulfuric Acid + Copper Sulfate
Sulfuric Acid + Ferrous Sulfate
Sulfuric Acid + Methanol
Sulfuric Acid + Nitric Acid
Sulfurous Acid
Water + Starch + Sulfur Dioxide
Water + Aluminum Sulfate
126
ANNEX 6.3
CORROSION RESISTANCE OF GASKET METALS*
S:
- :
M:
4:
Satisfactory
No Information
Monel
304 Stainless Steel
U: Unsatisfactory
C: Copper
N: Nickel
6: 316 Stainless Steel
SERVICE
Acetic Acid, Pure
Acetic Anhydride
Acetone
Acetylene
Air
Aluminum Chloride
Aluminum Sulphate
Alums
Ammonia, Cold
Ammonium Chloride
Ammonium Hydroxide
Ammonium Nitrate
Ammonium Phosphate
Ammonium Sulphate
Amyl Acetate
Amyl Alcohol
Aniline
Asphalt
Barium Chloride
Barium Hydroxide
Barium Sulphide
Beer
Beet Sugar, Liquors
Benzene
Benzine
Black Sulphate Liquor
Blast Furnace Gas
Borax
Boric Acid
Bromine
Butane
Butanol
C
F
U
S
S
F
F
F
U
U
U
F
F
F
S
U
S
U
U
S
S
S
S
F
U
F
F
U
S
* Please see note at the end of this table.
127
A
S
S
S
S
S
U
S
U
F
F
F
F
U
U
U
S
S
S
S
F
S
S
-
F: Fair
A: Aluminum
S: Iron and Carbon Steel
7: 347 Stainless Steel
M
S
S
S
S
S
S
F
F
S
F
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
N
F
S
F
S
S
S
S
S
-
S
U
S
S
S
F
U
U
S
S
S
U
S
S
S
S
S
S
S
S
S
S
U
U
S
S
4
F
F
S
S
S
U
F
F
S
F
S
S
S
S
S
S
S
F
S
S
S
S
S
S
S
S
S
U
-
6
F
F
S
S
U
F
F
S
F
S
S
S
S
S
S
S
S
S
S
S
S
S
S
U
S
-
7
F
S
S
F
F
F
S
S
S
S
S
S
S
S
S
U
-
ANNEX 6.3 (Continued)
CORROSION RESISTANCE OF GASKET METALS*
SERVICE
Butyl Acetate
Calcium Bisulphide
Calcium Chloride
Calcium Hydroxide
Caliche Liquors
Cane Sugar Liquors
Carbolic Acid
Carbon Dioxide
Dry
Wet
Carbon Bisulphide
Carbon Monoxide, Hot
Carbon Tetrachloride
Castor Oil
Chlorine
Chlorinated Solvents
Dry
Wet
Dry
Wet
Chloroacetic Acid
Chlorosulphonic Acid
Chromic Acid
Citric Acid
Coke Oven Gas
Copper Chloride
Copper Sulphate
Corn Oil
Cotton Seed Oil
Creosote
Cresylic Acid
Dowtherm
A
E
Ethers
Ethyl Acetate
Ethyl Cellulose
Ethyl Chloride
Ethylene Glycol
Ferric Chloride
Ferric Sulphate
C
S
U
S
S
U
S
F
U
U
S
U
S
U
U
U
S
S
S
S
U
S
S
S
S
S
U
U
* Please see note at the end of this table.
128
A
S
S
S
S
F
S
S
S
U
S
U
U
U
S
U
U
S
S
S
S
S
U
S
F
S
U
U
M
U
F
S
S
S
S
S
S
S
S
S
S
U
S
S
F
F
S
S
F
S
S
S
S
F
S
S
S
S
S
U
U
N
S
F
S
S
U
U
S
U
S
S
S
S
S
F
S
S
S
S
U
S
U
U
U
S
F
U
S
S
S
F
S
S
S
S
S
S
U
U
4
S
F
S
S
S
S
S
S
S
S
S
U
S
U
F
S
U
S
S
S
S
S
S
S
U
F
6
S
S
F
S
S
S
S
S
S
S
U
S
S
S
U
S
S
S
S
S
S
S
S
U
S
7
S
S
S
U
S
U
-
ANNEX 6.3 (Continued)
CORROSION RESISTANCE OF GASKET METALS*
SERVICE
Formaldehyde
Formic Acid
Freon
Fuel Oil
Furfural
Gasoline
Gelatin
Glucose
Glue
Glycerol, Glycerin
Green Sulphate Liquor
Hydrobromic Acid
Hydrochloric Acid
Hydrocyanic Acid
Cold
Hydrofluoric Acid
Hot
Less than 65%
More than 65%
Less than 65%
More than 65%
Hydrofluosilicic Acid
Hydrogen, Cold
Hydrogen Peroxide
Hydrogen Sulphide
Dry Cold
Hot
Wet Cold
Hot
Kerosene
Lacquers, Lacquer Solvents
Lactic Acid, Cold
Linseed Oil
Lubricating Oils, Refined
Magnesium Chloride
Magnesium Hydroxide
Magnesium Sulphate
Mercuric Chloride
Mercury
Methanol
Methyl Chloride
Milk
* Please see note at the end of this table.
C
F
F
S
S
S
S
S
F
U
F
U
F
S
U
U
U
U
U
S
S
S
F
U
S
U
U
S
S
129
A
F
U
S
S
S
S
S
S
S
U
U
U
U
U
U
S
S
S
S
S
S
S
S
S
U
U
U
U
S
S
M
S
S
S
S
S
S
S
S
S
S
S
F
S
S
S
F
S
U
S
U
S
S
S
S
S
F
S
S
U
S
S
S
S
N
U
U
F
S
U
S
U
S
F
S
U
S
S
F
U
S
S
S
S
S
S
S
U
U
U
F
U
U
S
U
S
U
U
S
U
S
S
F
S
S
S
S
S
S
4
S
F
S
S
S
S
S
S
S
U
S
U
U
U
U
U
S
S
S
S
S
S
S
S
F
S
S
U
S
S
-
6
S
F
S
S
S
S
S
S
U
S
U
U
U
U
U
S
S
S
S
S
S
F
S
F
S
S
U
S
S
S
7
U
U
U
U
U
S
S
S
S
F
S
U
-
ANNEX 6.3 (Continued)
CORROSION RESISTANCE OF GASKET METALS*
SERVICE
Mineral Oils
Natural Gas
Nickel Chloride
Nickel Sulphate
Nitric Acid
Concentrated
Diluted
Nitrobenzene
Oleic Acid
Oleum Spirits
Oxalic Acid
Oxygen
Cold
Hot 260 a 540ºC
Palmitic Acid
Petroleum Oils > 500F
Phosphoric Acid
Less than 45%
More than 45%, Cold
Picric Acid, Molten
Potassium Chloride
Potassium Cyanide
Potassium Hydroxide
Potassium Sulphate
Propane
Seawater
Sewage
Soap Solutions
Sodium Bicarbonate
Sodium Bisulphate
Sodium Carbonate
Sodium Chloride
Sodium Cyanide
Sodium Hydroxide
Sodium Hypochlorite
Sodium Metaphosphate
Sodium Nitrate
Sodium Perborate
Sodium Peroxide
C
S
U
U
U
U
F
U
S
S
U
S
U
F
F
U
S
U
U
S
F
F
U
U
F
-
* Please see note at the end of this table.
130
A
S
S
U
U
S
U
S
S
S
S
S
U
F
U
U
S
U
F
U
U
U
U
U
U
S
S
S
S
M
S
S
U
U
S
S
S
S
S
S
U
F
F
U
S
S
S
S
S
S
S
S
S
S
S
S
F
S
S
S
S
S
N
U
U
S
U
U
S
S
S
S
S
S
S
S
S
S
S
S
S
S
U
U
S
S
S
S
S
S
U
U
S
S
S
S
S
F
S
U
S
S
S
S
U
S
-
4
S
S
F
S
F
S
S
S
S
S
S
S
S
S
S
S
F
F
S
F
F
S
S
S
F
F
U
S
F
S
S
6
S
S
F
S
F
S
S
S
S
S
S
S
S
S
S
S
S
F
F
S
F
F
S
S
S
S
F
U
S
S
S
7
S
-
ANNEX 6.3 (Continued)
CORROSION RESISTANCE OF GASKET METALS*
SERVICE
Monobasic
Sodium Phosphate
Dibasic
Tribasic
Sodium Silicate
Sodium Sulphate
Sodium Sulphide
Sodium Thiosulphate
Soybean Oil
Stannic Chloride
Steam <200ºC
Stearic Acid
Sulphur
Sulphur Chloride
Sulphur Dioxide, dry
Sulphur Trioxide, dry
Less than 10%
10% to 75%
Sulphuric Acid
75% to 95%
Fuming
Sulphurous Acid
Tannic Acid
Tar
Tartaric Acid
Toluene
Trichloroethylene
Turpentine
Vinegar
Water
Whiskey and Wines
Zinc Chloride
Zinc Sulphate
Cold
Hot
Cold
Hot
Cold
Hot
C
S
U
S
U
U
U
S
U
U
S
S
U
U
U
U
U
U
S
S
S
U
U
A
S
S
U
U
U
U
U
S
S
S
S
U
U
U
S
S
S
S
S
U
-
M
S
S
S
S
S
F
U
S
S
U
S
S
U
U
S
S
S
S
S
S
S
S
S
N
S
S
S
S
S
F
U
S
S
U
S
U
U
U
U
U
S
S
-
S
S
S
S
S
S
S
S
S
U
U
U
U
F
S
S
S
S
S
U
-
4
S
S
S
S
S
S
F
S
S
F
U
U
U
S
U
U
F
S
S
S
F
S
F
U
S
6
S
S
S
S
S
S
S
S
S
S
F
S
F
F
F
U
S
U
F
F
F
S
S
S
S
U
S
7
S
S
S
-
*NOTE: Properties and application parameters shown throughout this Corrosion Resistance of Gasket
Metals Chart are typical. Your specific application should not be undertaken without independent
study and evaluation for suitability. For specific application recommendations consult with TEADIT.
Failure to select proper sealing products could result in property damage and/or serious personal injury.
Specifications subject to change without notice; this edition cancels all previous issues
131
132
CHAPTER
7
SPIRAL WOUND
GASKETS
1. SPIRAL WOUND GASKETS
Spiral Wound gaskets are made of a preformed metallic strip and a soft filler
wound together under pressure (Figure 7.1). When the gasket is seated, the filler
flows, filling up the imperfections of the flanges. The metal strip holds the filler, giving
mechanical resistance and resiliency to the gasket. Its “V” shape acts as a Chevron
Ring reacting to changes in pressure and temperature.
Spiral wound gaskets can be manufactured in several combinations of
materials, wide range of dimensions and shapes. They are widely utilized covering an
ample range of applications. ASME B16.5 flanges spiral wound gaskets are standardized
and produced in high volumes at a competitive price, when compared with other
gasket styles of same performance.
Figure 7.1
133
This Chapter presents the styles, design values, materials and other
information related to Spiral Wound gaskets.
2. MATERIALS
2.1. METALLIC STRIP
The metallic strip has a standardized thickness of 0.008 in (0.20 mm) and the
width according to the thickness of the gasket. Metals normally available on the
market in strip form are adequate for the manufacture of spiral wound gaskets. However
the most common materials are:
• Stainless steel AISI 304 and 304L: are the most widely used materials as a
result of their price and good resistance to corrosion.
• Stainless steel AISI 316 and 316L for chemical service.
• Stainless steel AISI 321 for high temperature service.
• Monel.
• Nickel 200.
• Inconel.
• Titanium
The characteristics and recommended uses of these materials are in Chapter
6 of this book.
2.2. FILLER
The filler material provides the sealability of the gasket. It is recommended
that the edge of the filler be flush with or above the metal strip. It should never be
below it.
2.2.1. FLEXIBLE GRAPHITE - GRAFLEX®
The characteristics of low permeability, thermal stability, low creep and
chemical resistance of Flexible Graphite makes it an excelent filler for spiral-wond gaskets.
In neutral or reducing services, it can be used from 330ºF (-200ºC) up to
5430ºF (3000ºC). Flexible graphite has very good chemical resistance. It can be used in
services with organic and inorganic acids and bases, solvents, hot wax and oils. It is
not recommended for extremely oxidizing compounds, such as concentrated nitric and
sulfuric acids, chromium and permanganate solutions, chlorine acid and liquid alkaline
metals. Temperatures above 660º F (450º C) in oxidizing services, including air, degrades
the material. In this case, it is necessary to encapsulate the gasket, protecting the
flexible graphite from direct contact with the oxidizing medium.
134
Flexible Graphite can be used in oxygen, in any concentration, up to 930º F
(500º C) as long as the sealing element is completely enclosed between the flanges.
The operational temperature limit for steam and hydrocarbons rich in hydrogen
is 1200º F (650º C). Flue gas service should be avoided at this temperature.
According to tests by The Pressure Vessel Research Committee (PVRC)
Flexible Graphite filled spiral wound gaskets are fire-safe. Its use is recommended in
refineries, chemical plants and services with flammable media.
2.2.2. PTFE
PTFE is used as a filler when higher chemical resistance is needed. The service
temperature range is from cryogenic up to 500º F (260º C). PTFE filled gaskets should
be confined in a grooved flange or with an inner reinforcing ring to increase its
mechanical resistance and avoid inward buckling of the winding.
2.2.3. MICA-GRAPHITE
A chlorite, graphite and cellulose based Beater Addition sealing paper with a
NBR latex binder. Due to its similar sealability and overall performance it has been
used as an Asbestos paper replacement in services up to 450º F (232º C). Above this
temperature it degrades. This material is not considered fire-safe. It is not recommended
for use in refineries, chemical plants or any service with flammable media where a firesafe gasket is required.
2.3. GUIDE RING
The guide ring, since it does not come into direct contact with contained
fluid, is normally made of carbon steel AISI 1010/1020. In extremely aggressive services
they can be made of the same material as the metal strip. Carbon steel guide rings are
electro-plated or painted to avoid corrosion.
3. GASKET DENSITY
In the process of manufacturing the gasket, the metallic strip and the filler are
wound together under pressure. Gaskets of different densities can be made by
combining this winding pressure and the thickness of the filler. As a general rule
gaskets of higher density are used with higher pressures as they have higher seating
stress.
4. GASKET DIMENSIONS
The gasket designed for non-standard flanges should be made in such a way
that the winding is always in contact with the sealing surface of the flanges. If the
winding is smaller than the inside diameter or larger than the outside diameter of the
135
flange it can break, losing its sealability. If the winding protrudes into the inside
diameter, pieces of the gasket can be carried out by the fluid, damaging the equipment.
The following recommendation should be used in dimensioning non-standard
gaskets.
• Gaskets confined by the inside and outside diameters
• Gasket inside diameter = inside diameter of the groove plus 1/16 in (1.6 mm).
• Outside diameter of the gasket = outside diameter of the groove less 1/16 in (1.6 mm).
• Gaskets confined only by the outside diameter:
• Inside diameter of the gasket = inside diameter of the female plus a minimum
of ¼ in (6.4 mm).
• Outside diameter of the gasket = outside diameter of the male less 1/16 in (1.6 mm).
• Gaskets for raised or flat faced flanges:
• Inside diameter of the gasket = inside diameter of the face plus a minimum of
¼ in (6.4 mm).
• Outside diameter of the gasket = outside diameter of the face less a minimum
of ¼ in (6.4mm).
The gasket outside and inside diameters should be adjusted in order to meet
the seating and operating stress recommendations in Chapter 2 of this book.
5. THICKNESS
The standard manufacturing thickness for spiral wound gaskets are 1/8 in
(3.2 mm), 0.175 in (4.45 mm), 3/16 in (4.76 mm) and ¼ in (6.4 mm).
The recommended thickness after seating should be in accordance with Table 7.1. The
final thickness indicated is what experience demonstrates to be the best for maximum
gasket resiliency.
136
Table 7.1
Gasket Thickness
Manufacturing Thickness - in (mm)
1/8 (3.2)
0.175 (4.45)
3/16 (4.76)
¼ (6.4)
Thickness after Seating - in (mm)
0.90 to 0.100 (2.3 to 2.5)
0.125 to 0.135 (3.2 a 3.4 )
0.125 to 0.145 (3.2 a 3.4)
0.180 to 0.200 (4.6 a 5.1)
6. DIMENSIONAL AND THICKNESS LIMITATIONS
Spiral wound gaskets can be manufactured in diameters ranging from ½ in (12
mm) up to 150 in (3800 mm). Table 7.2 shows maximum diameter and flange width as a
function of the gasket thickness. These limitations are generic and can vary according
to the metallic strip and the filler. Gaskets with dimensions other than shown are
unstable and difficult to manufacture and handle.
Table 7.2
Dimensional Limits
Thickness
in (mm)
1/8 (3.2)
0.175 (4.45)
3/16 (4.76)
¼ (6.4)
Maximum Inside Diameter
in (mm)
40 (1000)
70 (1800)
75 (1900)
150 (3800)
Maximum Width
in (mm)
¾ (19)
1 (25)
1 (25)
1 ¼ (32)
PTFE filled gaskets are less stable and can unwind during shipping and
handling. They have dimensional limits as shown in Table 7.3.
Table 7.3
Dimensional Limits for PTFE Filled Gaskets
Thickness
in (mm)
1/8 (3.2)
0.175 (4.45)
3/16 (4.76)
¼ (6.4)
Maximum Inside Diameter
in (mm)
20 (500)
45 (1100)
45 (1100)
150 (3800)
137
Maximum Width
in (mm)
¾ (19)
1 (25)
1 (25)
1 ¼ (32)
7. MANUFACTURING TOLERANCES
The manufacturing tolerances for the inside and outside diameters of spiral
wound gaskets are indicated in Table 7.4.
Table 7.4
Manufacturing Tolerances
Inside Diameter
in (mm)
Up to 8 (200)
8 to 24 (200 to 600)
24 to 35 (600 to 900)
35 to 60 (900 to 1500)
Over 60 (1500)
Diameter Tolerance – in (mm)
Inside
Outside
± 1/64 (± 0.4)
± 1/32 (± 0.8)
± 1/32 (± 0.8)
+1/16, -1/32 (+ 1.6, - 0.8)
± 3/64 (± 1.2)
± 1/16 (± 1.6)
± 1/16 (± 1.6)
± 3/32 (± 2.4)
± 3/32 (± 2.4)
± 1/8 (± 3.2)
The tolerance of the winding thickness is plus or minus 0.005 in (0.13 mm),
measured across the metallic strip. In gaskets with PTFE filler or with an internal
diameter less than 1 in (25 mm) or with a flange thickness greater than 1 in (25 mm) the
tolerance is plus 0.010 in (0.25 mm) minus 0.005 in (0.13 mm).
8. FINISH OF THE FLANGE SEALING SURFACE
As explained early in this Chapter, spiral wound gaskets depend on the
combined action of both metallic strip and filler for efficient sealing. When the gasket
is compressed, the filler flows, filling up the flange irregularities. The metallic strip
provides mechanical resistance and resiliency. Proper finishing of the sealing surface
is very important for good sealing. A scratched surface will be difficult to seal. A
smooth and polished surface can permit the gasket to inward buckle.
Although most of commercial flange finishes can be used, the experience
indicates that the following are the most appropriate.
Table 7.5
Finish of the Flange Sealing Surface
Media
General use
Dangerous Service and gases
Vacuum service
Flange Sealing Surface Finish - Ra
µm
µ in
6.3
250
3.2
125
2.0
80
Important: The sealing surfaces of flanges cannot have scratches or radial tool marks
going from the inside to the outside diameter. These irregularities make
the sealing very difficult for any style of gasket and especially for spiral
wound gaskets.
138
9. GASKET MAXIMUM SEATING STRESS
The maximum Spiral Wound Gasket Seating Stress (Sg), as explained in
Chapter 2 is 30,000 psi (210 MPa) for all Spiral Wound Gasket Styles, except for Style
913M, which is 43,000 psi (300 MPa). These values are for all filler materials.
10. GASKET STYLES
Spiral wound gaskets are manufactured in several geometrical forms such as
circular, oval, diamond, square, rectangular and others.
Guide rings or inner rings can be incorporated to the gaskets to better meet
specific service requirements.
11. STYLE 911 GASKETS
This is the simplest style of spiral wound gasket, consisting of a circular
winding without guide or inner rings. Spiral wound gaskets Style 911 are mainly used
in tongue and groove (Figure 7.2) or male and female (Figure 7.3) ASME B16.5 flanges.
They are also used in equipment with space and weight limitations.
Figure 7.2
Figure 7.3
11.1. DIMENSIONS
The dimensions of the gaskets for flanges ASME B16.5 are in Annex 7.1 at the
end of this Chapter.
For other applications, when it is necessary to have non-standard dimensions,
the winding should be designed to be totally under compression between the flanges.
The recommendations of Section 4 of this Chapter should be carefully followed.
139
11.2. THICKNESS
The standard thicknesses for style 911 gaskets is 1/8 in (3.2 mm). For large
diameters they can be manufactured in thickness of 3/16 in (4.76 mm) and ¼ in (6.4mm).
11.3. STYLE 911-M
A style 911-M gasket is a sealing winding with an inner ring (Figure 7.4). The
purpose of this ring is to fill out the space between the flanges, avoiding turbulence
in the flow of the fluid or as a protection against corrosion or erosion. It is also used
as a compression limit when the seating stress is greater than 30,000 psi (210 MPa)
and for vacuum rervice.
Gaskets with PTFE filler have a tendency to inward buckle thus the use of an
inner ring is recommended if the gasket is to be installed with a non-confined inside
diameter.
Figure 7.4
11.4. STYLE 911-T
Double jacketed bars are welded into the winding (Figure 7.5). They are used
in shell and tube heat exchangers with several passes. The bars are manufactured in
the same material and are plasma or spot welded to the winding. The thickness of the
bar is normally a little less than the winding to reduce the seating force of the gasket.
Style 911-T has a better sealability than conventional heat exchanger doublejacketed gaskets.
140
Figure 7.5
12. STYLE 913 GASKETS PER ASME B16.20 (API 601)
Gaskets per ASME B16.20 have the winding with an external guide on the
centering ring as shown in Figure 7.6. This solid metallic ring centralizes the gasket on
the flange surface, limits the compression and reinforces the gasket.
Several countries developed dimensional standards for this style of gasket. On
March 30th, 1993 the American Society of Mechanical Engineers (ASME) and the
American National Standards Institute (ANSI) issued a new edition of the ASME B16.20.
This edition includes spiral wound gaskets specifications and dimensions previously
covered by the API 601 which is no longer be published by the American Petroleum
Institute (API).
The ASME B16.20 (API 601) standard is one of the most used, worldwide. Gaskets
manufactured following the recommendations of the ASME B16.20 are produced in
large quantities. They are low priced compared with other gaskets of equivalent
performance. When specifying a metallic gasket they should be the first design option.
The use of another type of metal gasket should only be recommended if required by
the specific application conditions.
12.1. APPLICATION
The ASME B16.20 gaskets were designed for use in ASME B16.5 flanges or
ASME 16.47 (API 605 and MSS SP-44). Therefore, when ordering a spiral wound
gasket for these flanges dimensions are not necessary. It is enough to inform materials
141
for the metallic strip and filler, which should be compatible with the fluid to be sealed,
the nominal diameter and the pressure class of the flange. In Annexes 7.1 to 7.3, at the
end of this Chapter, are the dimensions, manufacturing tolerances for ASME B16.20
gaskets.
Figure 7.6
12.2. MATERIALS
The most common materials are:
• Metallic strip: all metals and alloys in strip can be used for spiral wound
gaskets. Gaskets are commercially available in stainless steels AISI 304,
316, 321 and 347, Monel, Inconel and Nickel.
• Filler: fillers commercially available are Flexible Graphite, Mica-Graphite,
PTFE and Asbestos.
• Guide ring: carbon steel AISI 1010/1020 or for very corrosive service, the
same material of the metallic strip.
• Inner ring: it is normally made with the same material of the metallic strip.
12.3. WINDING
The winding has the following construction:
• At least three initial plies of metallic strip without filler.
• The initial two plies of metallic strip shall be spot-welded circumferentially
with a minimum of three welds spaced at a maximum distance of three inches
(76.2 mm).
142
• The outer windings shall have a minimum of three plies of metallic without
filler, spotwelded circumferentially with a minimum of three welds, the last
being the terminal weld. The distance of the first weld from the terminal
weld shall be no greater than 1.5 in (38.1 mm).
• Up to four additional loose preformed metal windings beyond the terminal
weld may be used to retain the gasket into the guide ring. These free turns
are not included in determining the winding outside diameter.
• The winding thickness is 0.175 in (4.45 mm) plus or minus 0.005 in (0.127 mm)
measured across the metallic strip not including the filler, which may protrude
slightly beyond the metal.
12.4. INNER RING
To avoid an over compression due to high seating stress in high pressure
service it is necessary to use an inner ring as shown in Figure 7.7. It is also used to
reduce turbulence in the flange area. It is normally made of the same material as the
gasket metallic strip and increases substantially the gasket cost.
Its use is also mandatory in services with abrasive fluids. In high corrosive
services like Fluoridic Acid (HF) a PTFE inner ring is used to reduce the contact of the
gasket and inner surface of the flange with the fluid.
PTFE filled gaskets can inward buckle due to the low compressibility of the
PTFE. This buckling reduces the sealability of the gasket. It is mandatory to use inner
rings in PTFE filled gaskets regardless of size and pressure class.
Flexible Graphite gaskets can also have a tendency to inward buckle and it is
recommended to use inner rings. It is alo recommended to use inner rings for vacuam service.
Inner rings are mandatory for gaskets NPS 24 and larger class 900, NPS 12 and
larger class 1500 and NPS 4 and larger class 2500.
Inner ring thickness shall be 0.112 in (2.85 mm) to 0.131 in (3.33 mm). The
Annexes 7.1 to 7.3 have the inner ring dimensions as per the ASME B16.20.
Figure 7.7
143
12.5. IDENTIFICATION
The guide ring is permanently marked with lettering at least 1/8 in (3.2 mm)
height with the following information:
• Manufacturer’s name or trademark.
• Flange size (NPS).
• Pressure class.
• Winding metal abbreviation.
• Filler material abbreviation.
• Guide and inner ring metal abbreviation, except that the abbreviation may
be omitted when carbon steel is used for the guide ring and 304 stainless
steel is used for the inner ring.
• Standard identification: ASME B16.20.
• Flange identification for ASME B16.47 gaskets. For ASME B16.5. gaskets
the flange identification is not required.
12.6. COLOR CODING
The outer edge of the guide ring is painted in such a way as to help the
identification of the gasket in stock. The identification of the metallic strip material
should be painted continuously on the outer edge of the guide ring. The filler material
is identified with a minimum of four intermittent stripes equally spaced on the outer
edge of the guide ring. The color-coding is on Tables 7.7 and 7.8
Table 7.7
Metallic Strip Color Coding
Metallic Strip
AISI 304
AISI 316
AISI 347
AISI 321
Monel
Nickel
Carbon Steel
Inconel
Color
Yellow
Green
Blue
Turquoise
Orange
Red
Silver
Gold
Table 7.8
Filler Color Coding
Filler
Asbestos
PTFE
Flexible Graphite
Mica-Graphite
Color
Not painted
White
Gray
Pink
144
13. OTHER STANDARDS
There are several other standards like BS (United Kingdom), DIN (Germany),
JIS (Japan), etc.
Spiral Wound Gasket dimensions for DIN flanges are shown in the Annex 7.7.
14. STYLE 913 GASKET DESIGN
Following, are the recommendations that should be followed to design a style
913 gasket
Figure 7.8
14.1. WINDING
• Inside diameter (IG): equal to the inside diameter of flange raised face plus
a minimum of 1/4 in (6.4 mm).
• Outside diameter (OG): designed to meet the recommendations of seating
and operating stresses recommendations in Chapter 2. The maximum width
should follow the recommendations of Section 6 of this Chapter.
• Thickness (TK): standard manufacturing thickness are .175 in (4.45 mm), 3/
16 in (4.8 mm) and 1/4 in (6.4 mm). Whenever possible .175 in should be used.
• Manufacturing tolerances: are indicated in Section 7 of this Chapter.
145
14.2. GUIDE RING
• Thickness (TR): 1/8" (3,2mm).
• Inside diameter (IR): equal to the outside diameter of the winding minus
1/8 in (3.2 mm).
• Outside diameter (OR): equal to the bolt circle diameter minus the diameter
of the bolt.
• Manufacturing tolerance: of the outside diameter of the guide ring is plus
or minus 1/32 in (0.8 mm).
• Dimensional limitations: as a result of the manufacturing process limitations
and the stability of the winding, there are limitations. Minimum widths for
guide rings are according to indications on Table 7.9.
Table 7.9
Guide Ring Dimensional Limitations
Minimum Width in ( mm )
3/8 (10)
1/2 (12)
5/8 (16)
3/4 (20)
Guide Ring Inside Diameter in ( mm )
Up to 10 (250)
10 to 24 (250 to 600)
24 to 60 (600 to 1500)
60 (1500) or greater
14.3. INNER RING
As already mentioned, it is used to minimize turbulence in the gasket area,
avoid corrosion or erosion of the winding. In gaskets with PTFE filler, it avoids inward
buckling of the winding.
14.4. GASKETS WITH DOUBLE JACKETED BARS
Similar to the style 911-T with double-jacketed bars used in shell and tube
heat exchangers.
14.5. GUIDE RING WITH BOLT HOLES
To help the fitting on the equipment the guide ring can be manufactured with
the same overall diameter and drilling of the flanges.
15. STYLE 914
Style 914 spiral wound gaskets are windings in non-circular forms like oval,
rectangular and square with rounded corners, diamond, oblong or pear shaped as
shown in Figure 7.9.
146
Figure 7.9
15.1. APPLICATION
Style 914 gaskets are used in boiler handholes and manholes, equipment,
engine head-gaskets and exhaust systems.
15.2. DESIGNING
There is no specific standard for this type of gasket, depending on the design
calculations it can be made using the recommendations of the ASME Code.
When ordering 914 gaskets due to its odd shapes it is always necessary to
provide complete specifications, a drawing or a sample.
15.3. THICKNESS
The thickness available for style 914 gaskets are 1/8 in (3.2 mm), 0.175 in
(4.45 mm), 3/16 in (4.76 mm) and 1/4 in (6.4 mm).
147
15.4. GASKETS FOR BOILERS HANDHOLES AND MANHOLES
The majority of boiler manufacturers use the same size of manholes and
handholes in their equipment. Therefore even not being standardized some oval gaskets
are considered standard in the industry. The dimensions of these gaskets are shown
in Annex 7.4.
Figure 7.10
148
Annex 7.1
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
Nominal
Diameter
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
4
5
6
8
10
12
14
16
18
20
24
Gasket Outside Diameter per Pressure Class - inches
150, 300, 400, 600
1.25
1.56
1.88
2.38
2.75
3.38
3.88
4.75
5.88
7.00
8.25
10.38
12.50
14.75
16.00
18.25
20.75
22.75
27.00
149
900, 1500, 2500
1.25
1.56
1.88
2.38
2.75
3.38
3.88
4.75
5.88
7.00
8.25
10.13
12.25
14.50
15.75
18.00
20.50
22.50
26.75
Annex 7.1 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
Nominal
Diameter
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
4
5
6
8
10
12
14
16
18
20
24
Gasket Inside Diameter per Pressure Class - inches
150
0.75
1.00
1.25
1.88
2.13
2.75
3.25
4.00
5.00
6.13
7.19
9.19
11.31
13.38
14.63
16.63
18.69
20.69
24.75
300
0.75
1.00
1.25
1.88
2.13
2.75
3.25
4.00
5.00
6.13
7.19
9.19
11.31
13.38
14.63
16.63
18.69
29.69
24.75
400
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
4.75
5.81
6.88
8.88
10.81
12.88
14.25
16.25
18.50
20.50
24.75
600
0.75
1.00
1.25
1.88
2.13
2.75
3.25
4.00
4.75
5.81
6.88
8.88
10.81
12.88
14.25
16.25
18.50
20.50
24.75
900
(1)
(1)
(1)
(1)
(1)
(1)
(1)
3.75
4.75
5.81
6.88
8.75
10.88
12.75
14.00
16.25
18.25
20.50
24.75
1500
0.75
1.00
1.25
1.56
1.88
2.31
2.75
3.63
4.63
5.63
6.75
8.50
10.50
12.75
14.25
16.00
18.25
20.25
24.25
2500
0.75
1.00
1.25
1.56
1.88
2.31
2.75
3.63
4.63
5.63
6.75
8.50
10.63
12.50
(1)
(1)
(1)
(1)
(1)
Notes: 1. There are no Class 400 gaskets NPS ½ through NPS 3 (use Class 600), Class
900 gaskets NPS ½ through NPS 2 ½ (use Class 1500) and Class 2500 flanges
NPS 14 or larger.
2. Inner Rings are required for all PTFE filled gaskets and for Class 900 gaskets,
NPS 24; Class 1500 gaskets NPS 12 through NPS 24; and Class 2500, NPS 4
through NPS 12.
3. Tolerance in inches:
• Winding thickness:
± 0.005" – measured across the metallic
portion of the gasket not including the filler,
which may protrude slightly beyond the metal.
• Gasket outside diameter:
from ½” to 8"
: ± 0.03"
from 10" to 24" : + 0.06" – 0.003"
• Gasket inside diameter:
from ½” to 8"
: ± 0.016"
from 10" to 24" : ± 0.03"
150
Annex 7.1 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
Nominal
Diameter
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
4
5
6
8
10
12
14
16
18
20
24
Guide Ring Outside Diameter per Pressure Class - inches
150
1.88
2.25
2.63
3.00
3.38
4.13
4.88
5.38
6.88
7.75
8.75
11.00
13.38
16.13
17.75
20.25
21.63
23.88
28.25
300
2.13
2.63
2.88
3.25
3.75
4.38
5.13
5.88
7.13
8.50
9.88
12.13
14.25
16.63
19.13
21.25
23.50
25.75
30.50
400
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
7.00
8.38
9.75
12.00
14.13
16.50
19.00
21.13
23.38
25.50
30.25
600
2.13
2.63
2.88
3.25
3.75
4.38
5.13
5.88
7.63
9.50
10.50
12.63
15.75
18.00
19.38
22.25
24.13
26.88
31.13
900
(1)
(1)
(1)
(1)
(1)
(1)
(1)
6.63
8.13
9.75
11.38
14.13
17.13
19.63
20.50
22.63
25.13
27.50
33.00
1500
2.50
2.75
3.13
3.50
3.88
5.63
6.50
6.88
8.25
10.00
11.13
13.88
17.13
20.50
22.75
25.25
27.75
29.75
35.50
2500
2.75
3.00
3.38
4.13
4.63
5.75
6.63
7.75
9.25
11.00
12.50
15.25
18.75
21.63
(1)
(1)
(1)
(1)
(1)
NOTES: 1. There are no Class 400 gaskets NPS ½ through NPS 3 (use Class 600), Class
900 gaskets NPS ½ through NPS 2 ½ (use Class 1500) and Class 2500 flanges
NPS 14 or larger.
2. Guide Ring outside diameter tolerance: ± 0.03"
151
Annex 7.1 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
Nominal
Diameter
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
4
5
6
8
10
12
14
16
18
20
24
Inner Ring Inside Diameter per Pressure Class - inches
150
0.56
0.81
1.06
1.50
1.75
2.19
2.62
3.19
4.19
5.19
6.19
8.50
10.56
12.50
13.75
15.75
17.69
19.69
23.75
300
0.56
0.81
1.06
1.50
1.75
2.19
2.62
3.19
4.19
5.19
6.19
8.50
10.56
12.50
13.75
15.75
17.69
19.69
23.75
400
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
4.19
5.19
6.19
8.25
10.25
12.50
13.75
15.75
17.69
19.69
23.75
600
0.56
0.81
1.06
1.50
1.75
2.19
2.62
3.19
4.19
5.19
6.19
8.25
10.25
12.50
13.75
15.75
17.69
19.69
23.75
900
(1)
(1)
(1)
(1)
(1)
(1)
(1)
3.19
4.19
5.19
6.19
7.75
9.69
11.50
12.63
14.75
16.75
19.00
23.25
1500
0.56
0.81
1.06
1.31
1.63
2.06
2.50
3.19
4.19
5.19
6.19
7.75
9.69
11.50
12.63
14.50
16.75
18.75
22.75
2500
0.56
0.81
1.06
1.31
1.63
2.06
2.50
3.19
4.19
5.19
6.19
7.75
9.69
11.50
(1)
(1)
(1)
(1)
(1)
NOTES: 1. There are no Class 400 gaskets NPS ½ through NPS 3 (use Class 600), Class
900 gaskets NPS ½ through NPS 2 ½ (use Class 1500) and Class 2500
flanges NPS 14 or larger.
2. Inner Ring thickness: 0.117" to 0.131".
3. Inner Ring Inside diameter tolerance: from 1¼” to 3": ± 0.03
4" and larger: ± 0.06
152
Annex 7.2
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series A
Gasket Dimensions per Pressure Class - inches
Nominal
Diameter
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
DI
26.50
28.50
30.50
32.50
34.50
36.50
38.50
40.50
42.50
44.50
46.50
48.50
50.50
52.50
54.50
56.50
58.50
60.50
150
DE
27.75
29.75
31.75
33.88
35.88
38.13
40.13
42.13
44.25
46.38
48.38
50.38
52.50
54.50
56.50
58.50
60.50
62.50
DA
30.50
32.75
34.75
37.00
39.00
41.25
43.75
45.75
48.00
50.25
52.25
54.50
56.50
58.75
61.00
63.25
65.50
67.50
DI
27.00
29.00
31.25
33.50
35.50
37.63
38.50
40.25
42.25
44.50
46.38
48.63
51.00
53.00
55.25
57.25
59.50
61.50
153
300
DE
29.00
31.00
33.25
35.50
37.50
39.63
40.00
42.13
44.13
46.50
48.38
50.63
53.00
55.00
57.25
59.25
61.50
63.50
DA
32.88
35.38
37.50
39.63
41.63
44.00
41.50
43.88
45.88
48.00
50.13
52.13
54.25
56.25
58.75
60.75
62.75
64.75
DI
27.00
29.00
31.25
33.50
35.50
37.63
38.25
40.38
42.38
44.50
47.00
49.00
51.00
53.00
55.25
57.25
59.25
61.75
400
DE
29.00
31.00
33.25
35.50
37.50
39.63
40.25
42.38
44.38
46.50
49.00
51.00
53.00
55.00
57.25
59.25
61.25
63.75
DA
32.75
35.13
37.25
39.50
41.50
44.00
42.25
44.38
46.38
48.50
50.75
53.00
55.25
57.25
59.75
61.75
63.75
66.25
Annex 7.2 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series A
Gasket Dimensions per Pressure Class - inches
Nominal
Diameter
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
DI
27.00
29.00
31.25
33.50
35.50
37.63
39.00
41.25
43.50
45.75
47.75
50.00
52.00
54.00
56.25
58.25
60.50
62.75
600
DE
29.00
31.00
33.25
35.50
37.50
39.63
41.00
43.25
45.50
47.75
49.75
52.00
54.00
56.00
58.25
60.25
62.50
64.75
DA
34.13
36.00
38.25
40.25
42.25
44.50
43.50
45.50
48.00
50.00
52.25
54.75
57.00
59.00
61.25
63.50
65.50
68.25
DI
27.00
29.00
31.25
33.50
35.50
37.75
40.75
43.25
45.25
47.50
50.00
52.00
900
DE
29.00
31.00
33.25
35.50
37.50
39.75
42.75
45.25
47.25
49.50
52.00
54.00
DA
34.75
37.25
39.75
42.25
44.75
47.25
47.25
49.25
51.25
53.88
56.50
58.50
There are no Class 900 flanges
NPS 50 and larger
1. Inner Rings are required for all PTFE filled gaskets and for Class 900, NPS 26 through
NPS 48.
2. Tolerance in inches:
± 0.005" – measured across the metallic portion of the
gasket not including the filler, which may protrude
slightly beyond the metal.
• Gasket outside diameter: ± 0.06"
• Winding thickness:
• Gasket inside diameter:
from 26" to 34" : ± 0.03"
36" and larger : ± 0.05"
• Guide Ring outside diameter : ± 0.03"
154
Annex 7.2 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series A
Nominal
Diameter
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
Inner Ring Inside Diameter per Pressure Class - inches
150
25.75
27.75
29.75
31.75
33.75
35.75
37.75
39.75
41.75
43.75
45.75
47.75
49.75
51.75
53.50
55.50
57.50
59.50
300
25.75
27.75
29.75
31.75
33.75
35.75
37.50
39.50
41.50
43.50
45.38
47.63
49.00
52.00
53.25
55.25
57.00
60.00
400
26.00
28.00
29.75
32.00
34.00
36.13
37.50
39.38
41.38
43.50
46.00
47.50
49.50
51.50
53.25
55.25
57.25
59.75
Tolerances:
Inner Ring thickness: 0.117" to 0.131".
Inner Ring Inside diameter tolerance: ± 0.12".
155
600
25.50
27.50
29.75
32.00
34.00
36.13
37.50
39.75
42.00
43.75
45.75
48.00
50.00
52.00
54.25
56.25
58.00
60.25
900
26.00
28.00
30.00
32.00
34.00
36.25
39.75
41.75
43.75
45.50
48.00
50.00
There are
no Class
900 flanges
NPS 50 and
larger.
Annex 7.3
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series B
Gasket Dimensions per Pressure Class - inches
Nominal
Diameter
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
DI
26.50
28.50
30.50
32.50
34.50
36.50
38.37
40.25
42.50
44.25
46.50
48.50
50.50
52.50
54.50
56.88
59.07
61.31
150
DE
27.70
29.50
31.50
33.50
35.75
37.75
39.75
41.88
43.88
45.88
48.19
50.00
52.19
54.19
56.00
58.18
60.19
62.44
DA
28.56
30.56
32.56
34.69
36.81
38.88
41.13
43.13
45.13
47.13
49.44
51.44
53.44
55.44
57.63
59.63
62.19
64.19
DI
26.50
28.50
30.50
32.50
34.50
36.50
39.75
41.75
43.75
45.75
47.88
49.75
51.88
53.88
55.25
58.25
60.44
62.56
156
300
DE
28.00
30.00
32.00
34.00
36.00
38.00
41.25
43.25
45.25
47.25
49.38
51.63
53.38
55.38
57.25
60.00
61.94
64.19
DA
30.38
32.50
34.88
37.00
39.13
41.25
43.25
45.25
47.25
49.25
51.88
53.88
55.88
57.88
60.25
62.75
65.19
67.19
DI
26.25
28.13
30.13
32.00
34.13
36.13
38.25
40.38
42.38
44.50
47.00
49.00
51.00
53.00
55.25
57.25
59.25
61.75
400
DE
27.50
29.50
31.75
33.88
35.88
38.00
40.25
42.38
44.38
46.50
49.00
51.00
53.00
55.00
57.25
59.25
61.25
63.75
DA
29.38
31.50
33.75
35.88
37.88
40.25
42.25
44.38
46.38
48.50
50.75
53.00
55.25
57.25
59.75
61.75
63.75
66.25
Annex 7.3 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series B
Gasket Dimensions per Pressure Class - inches
Nominal
Diameter
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
DI
26.13
27.75
30.63
32.75
35.00
37.00
39.00
41.25
43.50
45.75
47.75
50.00
52.00
54.00
56.25
58.25
60.50
62.75
600
DE
28.13
29.75
32.63
34.75
37.00
39.00
41.00
43.25
45.50
47.75
49.75
52.00
54.00
56.00
58.25
60.25
62.50
64.75
DA
30.13
32.25
34.63
36.75
39.25
41.25
43.50
45.50
48.00
50.00
52.25
54.75
57.00
59.00
61.25
63.50
65.50
68.25
DI
27.25
29.25
31.75
34.00
36.25
37.25
40.75
43.25
45.25
47.50
50.00
52.00
900
DE
29.50
31.50
33.75
36.00
38.25
39.25
42.75
45.25
47.25
49.50
52.00
54.00
DA
33.00
35.50
37.75
40.00
42.25
44.25
47.25
49.25
51.25
53.88
56.50
58.50
There are no Class 900 flanges
NPS 50 and larger.
1. Inner Rings are required for all PTFE filled gaskets and for Class 900, NPS 26 through
NPS 48.
2. Tolerance in inches:
± 0.005" – measured across the metallic portion of the
gasket not including the filler, which may protrude
slightly beyond the metal.
Gasket outside diameter: ± 0.06"
Winding thickness:
Gasket inside diameter:
from 26" to 34" : ± 0.03"
36" and larger : ± 0.05"
Guide Ring outside diameter: ± 0.03"
157
Annex 7.3 (Continued)
Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series B
Nominal
Diameter
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
Inner Ring Inside Diameter per Pressure Class - inches
150
25.75
27.75
29.75
31.75
33.75
35.75
37.75
39.75
41.75
43.75
45.75
47.75
49.75
51.75
53.50
55.50
57.50
59.50
300
25.75
27.75
29.75
31.75
33.75
35.75
37.50
39.50
41.50
43.50
45.38
47.63
49.00
52.00
53.25
55.25
57.00
60.00
400
26.00
28.00
29.75
32.00
34.00
36.13
37.50
39.38
41.38
43.50
46.00
47.50
49.50
51.50
53.25
55.25
57.25
59.75
Tolerances:
Inner Ring thickness: 0.117" to 0.131".
Inner Ring Inside diameter tolerance: ± 0.12".
158
600
25.50
27.50
29.75
32.00
34.00
36.13
37.50
39.75
42.00
43.75
45.75
48.00
50.00
52.00
54.25
56.25
58.00
60.25
900
26.00
28.00
30.25
32.00
34.00
36.25
39.75
41.75
43.75
45.50
48.00
50.00
There are
no Class
900 flanges
NPS 50 and
larger.
Annex 7.4
Style 914 Spiral Wound Gaskets
Inside Dimensions - in
A
B
11
14
11
14
11
14
11
15
11
15
11
15
11
15
11
15
11
15
11 ¼
15 ½
12
16
12
16
12
16
12
16
12
16
12
16
12
16
12
16
Width - W - in
Thickness - E - in
3/4
1
1 ¼
½
¾
¾
1
1 ¼
1 ¼
¾
5/16
½
¾
7/8
1
1
1 ¼
1 1/4
3/16
3/16
3/16
3/16
3/16
¼
3/16
3/16
¼
3/16
3/16
3/16
3/16
3/16
3/16
¼
3/16
1/4
159
Annex 7.5
Style 911 for Tongue and Groove Flanges
Nominal
Diameter
½
¾
1
1¼
1½
2
2½
3
3½
4
5
6
8
10
12
14
16
18
20
24
Gasket Dimensions - in
Small
Large
Ee
1 3 /8
1 11/16
2
2 ½
2 7 /8
3 5 /8
4 1 /8
5
5 ½
6 3/16
7 5/16
8 ½
10 5/8
12 ¾
15
16 ¼
18 ½
21
23
27 ¼
Ie
1
1 5/16
1 ½
1 7/ 8
2 1/8
2 7/ 8
3 3/ 8
4 ¼
4 ¾
5 3/16
6 5/16
7 ½
9 3/ 8
11 ¼
13 ½
14 ¾
17
19 ¼
21
25 ¼
Standard thickness: 3.2 mm (1/8").
160
Ie
1
1 5/16
1 ½
1 7 /8
2 1 /8
2 7 /8
3 3 /8
4 ¼
4 ¾
5 3/16
6 5/16
7 ½
9 3 /8
11 ¼
13 ½
14 ¾
16 ¾
19 ¼
21
25 ¼
Ee
1 3 /8
1 11/16
1 7 /8
2 ¼
2 ½
3 ¼
3 ¾
4 5 /8
5 1/8
5 11/16
6 13/16
8
10
12
14 ¼
15 ½
17 5/8
20 1/8
22
26 ¼
Annex 7.6
Style 911 for Male and Female ASME B16.5 Flanges
Nominal
Diameter
¼
½
¾
1
1¼
1½
2
2½
3
3½
4
5
6
8
10
12
14
16
18
20
24
Gasket Dimensions - inches
Class 2500 psi
Class 150 to 1500 psi
Ee
Ee
Ie
Ie
1
½
13
1 3/ 8
1 3/8
/16
1
1 11/16
1 1/16
1 11/16
1 5/16
2
1 ¼
2
1 ½
2 ½
1 5/8
2 ½
1 7/8
2 7/ 8
1 7/8
2 7/8
2 1/8
5
3
7
3 /8
2 /8
3 5/8
2 /8
1
3
4 /8
3
4 1/8
3 /8
5
3 ¾
5
4 ¼
5 ½
4 ¾
3
3
6 /16
4 ¾
6 3/16
5 /16
5
5
7 /16
5 ¾
7 5/16
6 /16
8 ½
6 ¾
8 ½
7 ½
10 5/8
8 ¾
10 5/8
9 3/8
12 ¾
10 ¾
12 ¾
11 ¼
13
15
15
13 ½
16 ¼
14 ¾
18 ½
17
21
19 ¼
23
21
27 ¼
25 ¼
Standard thickness: 3.2 mm (1/8").
161
Annex 7.7
Gasket Dimensions for Styles 913 and 913M per DIN 2699
DN
D1
D2
D3 – Pressure
Class -bar
10
15
20
25
32
40
50
65
80
100
125
150
175
200
250
300
350
400
450
500
600
700
800
900
1000
16
20
28
35
43
50
61
77
90
115
140
167
191
215
267
318
360
410
460
510
610
710
810
910
1010
24
28
36
43
51
58
73
89
102
127
152
179
203
227
279
330
380
430
480
530
630
730
830
930
1030
2 to 64 100 to 250
36
40
50
57
67
74
91
109
111
122
126
147
151
174
178
201
205
229
235
253
259
307
315
358
366
410
418
462
470
516
566
628
666
770
874
974
1078
D4 – Pressure Class - bar
25
254
284
340
400
457
514
624
731
822
942
1042
1154
162
40
46
51
61
71
82
92
107
127
142
168
194
224
265
290
352
417
474
546
628
63
113
138
148
174
210
247
277
309
364
424
486
543
100
287
391
458
160
56
61
250
67
72
82
83
103
119
144
154
180
217
257
284
324
388
458
109
124
154
170
202
242
284
316
358
442
CHAPTER
8
JACKETED GASKETS
1. DESCRIPTION
A Jacketed Gasket is comprised of a soft pliable core inside a metallic jacket
as shown in Figure 8.1. This Chapter covers several styles and applications.
Figure 8.1
163
2. METALLIC JACKET
Almost any metal or alloy found in sheet form can be used as a jacket; its
choice must take into consideration the fluid to be sealed as explained in Chapter 6 of
this book. The metallic jacket is 0.016 in (0.4 mm) to 0.024 in (0.6 mm) thick.
3. FILLER
The standard filler material is Flexible Graphite. Other fillers like ceramic,
asbestos, mica-graphite, PTFE or another metal can be used.
4. DESIGN
The following recommendations are based on successful practical applications:
• Gaskets confined by the inside and outside diameters:
• Gasket inside diameter = groove inside diameter plus 1/16 in (1.6 mm).
• Gasket outside diameter = groove outside diameter less 1/16 in (1.6 mm).
• Gaskets confined by outside diameter:
• Gasket inside diameter = flange inside diameter plus a minimum of 1/8 in (3.2 mm).
• Gasket outside diameter = groove outside diameter less 1/16 in (1.6 mm).
• Non confined gaskets:
• Gasket inside diameter = flange inside diameter plus 1/8 in (3.2 mm).
• Gasket outside diameter = bolt circle diameter less bolt diameter.
• Gasket width: to have adequate seating stress, the design recommendations
of Chapter 2 should be followed.
5. STYLES AND APPLICATIONS
5.1. STYLE 920
The style 920 is a round single jacket gasket as shown in Figure 8.2. Used in
applications where the seating stress and width are limited. It can be manufactured in
circular or oval shape. The maximum gasket width is 1/4 (6.4 mm) and the standard
thickness is 3/32 in (2.4 mm).
164
Figure 8.2
5.2. STYLE 923
The style 923 is a flat double jacket gasket as shown in Figure 8.3. Its most
typical applications are as pipe flange gaskets and in Heat Exchangers. ASME B16.20
shows the gasket dimensions for ANSI B16.5 flanges. The standard thickness is 1/8 in
(3.2 mm). Section 7 of this Chapter deals with the gaskets for Heat Exchangers.
Style 923 gaskets are also used in large size reactors in chemical plants. Another
important use is for flanges in the large, low pressure ducting in Steel Mill Blast
Furnaces. To compensate for distortions and irregularities of these flanges gaskets
have the thickness from 5/32 in (4 mm) to 1/4 in (6 mm).
Figure 8.3
165
5.3. STYLE 926
Similar to style 923 but the metallic jacket is corrugated as shown in Figure
8.4. The corrugations act as a labyrinth increasing the sealability. For ASME B16.5
flanges, the gasket dimensions are also covered by the ASME B16.20 standard.
Figure 8.4
5.4. STYLE 929
Similar to style 926 with a grooved metallic filler (Figure 8.5). Used in
applications where it is necessary to have a gasket without non-metallic materials,
temperature limits and chemical resistance depend upon of the metal only
Figure 8.5
166
6. GASKETS FOR HEAT EXCHANGERS
6.1. HEAT EXCHANGERS
There are several kinds of Heat Exchangers, some of them so incorporated in
our life style that we hardly notice them, like car radiators or home heating units. All of
them transfer heat from one fluid to the other, cooling (radiator) or heating (home
heating), according to the process needs.
In industry there are several kinds of Heat Exchangers, some have specific
names like radiators, boilers, chillers, etc. However when we refer to a Heat Exchanger
generically we may be referring to any of them. However the term Heat Exchanger, in
most process industries is referred to as the “Shell and Tube Heat Exchanger”. As the
name implies, it is equipment that has a “shell” and a bundle of “ tubes”. One of the
fluids flows inside the shell and outside the tubes and the other fluid inside the tubes.
6.2. TEMA STANDARD
The great majority of the Shell and Tube Heat Exchangers are manufactured
following the recommendations of the “Standards of the Tubular Exchanger
Manufactures Association – TEMA”, which sets the guidelines for design,
construction, testing, installation and maintenance of this equipment. The TEMA
Standard defines three classes of Heat Exchangers:
• Class R: are designed for the generally severe requirements of Petroleum and related
processing applications. For this service double jacketed metal (Teadit Style 923, 926
or 927) or solid metal (Teadit Style 940, 941 or 942) gaskets shall be used for internal
floating head joints, all joints for pressure of 300 psi and over, and for all joints in
contact with hydrocarbons.
• Class B: are designed for the chemical process service. For this service double
jacketed metal (Teadit Style 923, 926 or 927) or solid metal (Teadit Style 940, 941 or 942)
gaskets shall be used for internal floating head joints, all joints for pressure of 300 psi
and over. For 300 psi and lower, composition gaskets may be used for external joints,
unless temperature and the corrosive nature of the contained fluid indicates otherwise.
• Class C: are designed for the generally moderate requirements of commercial and
general process applications. Gasket selection follows the same requirements of Class
B service.
6.3. GASKETS STYLE 923
Style 923 is the gasket used most in shell and tube heat exchangers. It can be
manufactured in a wide range of sizes, shapes and with bars for heat exchangers with
several passages. The primary seal is at the inside diameter where there is a higher
gasket density after seating. The outside of the gasket is also denser after seating and
acts as a secondary seal. A nubbin of 1/64 in (0.4mm) height and 1/8 in (3.2 mm) width
can be machined on the face of the flange to increase gasket sealability. Figure 8.6
shows the gasket and how it should be installed in Tongue and Groove flanges.
167
Figure 8.6
To increase the gasket sealability a 1/64" (0.4 m) high by 1/8" (3.2 mm) wide
nubbin is machined on the flange surface. This nubbin pressing where the gasket is
thinner increases the seating stress in this area. The Figure 8.7 shows how a gasket is
installed in a flange with a nubbin.
Figure 8.7
168
6.4. MATERIALS
Gaskets for heat exchangers can be manufactured in almost any metal or alloy
available in sheets of 0.016 in (0.4 mm) to 0.020 in (0.5 mm) thick. The choice of jacket
material should take into account the operating conditions and the recommendations
in Chapter 6 of this book. The standard filler is Flexible Graphite.
6.5. GASKETS WITH INTEGRAL BARS
Traditionally double-jacketed gaskets for heat exchangers are manufactured
with integral bars as shown in the Figure 8.8. There is a radius of concordance between
the bars and the inside diameter of the gasket.
Figure 8.8
169
6.6. GASKETS WITH WELDED BARS
Gaskets with welded bars (Figure 8.9) avoid one of the greatest problems of
conventional gaskets, which are the cracks in the radius of concordance area as shown
in Figure 8.8.
The gasket material can crack due to the stresses during the forming of the
radius. The primary seal as explained in Section 1 is broken. The secondary seal
provides all the sealing.
The greater area of the “radius of concordance” region decreases the gasket
seating stress and thus reduces the sealability in the radius region.
Gaskets with welded bars as shown in Figure 8.9 have been developed to
overcome the above deficiencies. The primary and secondary seal are 360º around the
gasket. The gasket has a greater sealability, reducing leaks to the environment around
the equipment.
The bar seal between the heat exchanger passes. There is a small leak path at
the end of each bar. However due to the low pressure differential, these leaks do not
change the overall performance of the equipment.
The bars are Plasma or TIG welded with spot welds at each end. This way the
bars are attached without reducing the gasket sealability. These welds should be soft
and small to avoid areas of increased resistance to seating.
Figure 8.9
170
6.7. DESIGN
The Annex 8.1 shows the most common shapes of gaskets for heat exchangers.
The normal dimensions for heat exchanger gaskets are:
• Gasket and bar width: 3/8 in (10 mm), 1/2 in (12.7 mm) and 5/8 in (15.9 mm).
• Gasket thickness: 3.2 mm (1/8 pol).
• Assembly gap: to allow the seating and assembly of the gasket it is
recommended there be a gap of 1/8 in (3.2 mm) between the gasket and its
groove.
Table 8.1
Radius of Concordance
Gasket Material
Aluminum
Copper
Carbon Steel
Stainless Steel
Nickel
Radius of Concordance minimum - mm
6
8
10
12
10
6.8. MANUFACTURING TOLERANCES
Gaskets have to follow the recommendation of Tables 8.2 and Figure 8.10.
Table 8.2
Manufacturing Tolerances
Tolerance - in
Characteristic
± 1/16 (average)
± 1/16
5/32
1/16
Gaskets without bars
Gaskets with bars
Gaskets without bars
Outside Diameter Eccentricity Gaskets with bars
Outside Diameter (A)
Width (B)
Thickness (E)
Overlap (S)
Partition Bar Width (C)
+0.0, -1/32
+1/32, 0.0
Equal to or larger than 1/8
+0.0, -1/32
Partition Bar Location (F)
± 1/32
171
Figure 8.10
6.9. PARTITION BAR WELDING
Partitions are welded in such a way it does not protrude beyond the gasket
sealing surface, as shown in figures 8.11.
Figure 8.11
172
7. STYLE 927 GASKETS FOR HEAT EXCHANGERS
Style 927 gaskets are manufactured covering both sides of a Style 923 gasket
with Flexible Graphite Corrugated Tape, as shown in Figure 8.12. The gasket
construction follows the recommendations of Section 6 of this Chapter.
The Flexible Graphite cover increases the gasket sealability, especially if the
flange sealing surfaces have pitting, tool marks or other small irregularities often
found in these kinds of equipment.
The Style 927 gaskets combine the welded bar construction advantages with
the excellent sealability of the Flexible Graphite, which fill up the small irregularities,
providing a high sealability seal. It is recommended to use them if the operational
conditions are suitable.
Corrugated Flexible
Graphite Tape
Style 923 Gasket
Figure 8.12
173
Annex 8.1
Schedule of Standard Heat Exchanger Gaskets
174
Annex 8.1 (Continued)
Schedule of Standard Heat Exchanger Gaskets
175
Annex 8.1 (Continued)
Schedule of Standard Heat Exchanger Gaskets
176
CHAPTER
9
METALLIC GASKETS
1. METALLIC GASKETS
Metallic gaskets can be divided into two principal categories: Flat gaskets
and Ring-Joint gaskets as shown in Figure 9.1. Both are manufactured from a metal or
alloy without a soft filler.
Figure 9.1
2. FLAT METALLIC GASKETS
Defined as gaskets of relatively small thickness compared with its width.
They are normally produced from a sheet with or without a machined sealing surface.
To have an effective seal, the flange must force the gasket material; therefore
the gasket must always be softer than the flange.
177
3. MATERIALS
Any material available in sheet that can be cut, machined, or stamped can be
used. The recommendations in Chapter 6 of this book should be followed to specify
the material of the gasket.
To manufacture gaskets larger than the maximum sheet size, it is necessary to
weld the gasket. This welding must not be harder than the flange material or it will
damage the sealing surface.
4. FINISH OF THE FLANGE SEALING SURFACE
For better performance, the use of flanges with a fine finish is recommended.
The roughness should be 63 µin Ra (1.6 µm Ra). Under no circumstances should the
finish exceed 125 µin Ra (3.2 µm Ra). Scratches or radial tool marks are practically
impossible to seal with metallic gaskets.
5. STYLES OF FLAT METALLIC GASKETS
5.1. STYLE 940
The style 940 (Figure 9.2) is a metallic gasket that has a smooth sealing surface
and can be manufactured practically in any shape. Their typical applications are in
valves, heat exchangers, hydraulic presses and tongue and groove flanges. The strong
points are mechanical and chemical attack resistance and they can be used in elevated
temperature and pressure service.
The width of the gasket sealing surface should be at least equal to 1.5 times
its thickness.
Figure 9.2
178
These gaskets depending upon their material have high maximum seating
stress. The values for the maximum and minimum seating stress are shown in Table 9.1.
Table 9.1
Seating Stress for Style 940 Gaskets
Seating Stress
psi
Material
Soft Iron
AISI 1006/1008
AISI 1010/1020
AISI 304/316/321
AISI 309
Nickel
Copper
Aluminum
Mínimum
34000
34000
38500
48600
58000
27500
19600
0000
Máximum
76000
76000
87000
109000
130000
74000
43500
20300
5.2. STYLE 941
Style 941 is a flat gasket with concentric grooves as shown in Figure 9.3.
They combine the advantage of the style 940 with a reduced area of contact
with the flange to increase the seating stress.
Used when a metallic gasket is required but the available seating force is not
enough to seal a style 940. Minimum manufacturing thickness: 3/64 in (1.2 mm).
Figure 9.3
179
5.3. STYLE 943
If the service requires the use of style 941 but the flanges need to be protected to
avoid being damaged, the 941 gasket can be jacketed as shown in (Figure 9.4).
Figure 9.4
5.4. STYLE 900
Style 900 is a corrugated metal gasket as shown in Figure 9.5. They are used
in low pressure applications where there are limitations of weight and space. The
thickness of the sheet should be 0.010 in (0.25 mm) to 0.04 in (1 mm) depending on the
metal and number of corrugations. Due to the thickness of the sheet, the force required
to seat the gasket is greatly reduced when compared with gasket styles 940 and 941.
A minimum of 3 corrugations is necessary to obtain satisfactory sealing. A
small flat area on the inside and outside diameters of the gasket is recommended to
increase its mechanical strength. The corrugation pitch can vary between 0.045 in (1.1
mm) to 1/4 in (6.4 mm). The total thickness of the gasket is 40% to 50% of the corrugation
pitch. The metal used determines the service temperature limit. Maximum service
pressure: 500 psi.
Figure 9.5
180
5.5. METALBEST STYLE 905
Metalbest Style 905 is a corrugated gasket style 900 metal core with Flexible
Graphite facings as shown in Figure 9.6. It combines the sealing properties of the
Flexible Graphite with the extrusion resistance of the corrugated metal core. It is
designed to maintain a positive seal through thermo-cycling and shock load conditions.
These gaskets have passed industry fire tests, which are relative indicators of gasket’s
ability to resist fire conditions.
Figure 9.6
Style 905 gaskets can also be manufactured with a cover of Ceramic Fiber felt
(Figure 9.7), for use with large size ducts at high temperature and low pressure like in
Blast Furnaces and gas turbine exhaust. The metal thickness is 0.020 in (0.5 mm) and
the corrugation pitch is 5/32 in (4 mm), 3/16 in (4.8 mm) or 1/4 in (6.4 mm) depending on
the width of the gasket.
Figure 9.7
181
5.5.1. STYLE 905 GASKETS FOR ASME B16.5 FLANGES
Style 905 gaskets with Flexible Graphite facings have gained popularity in the
marketplace in Class 150 and 300 ASME B16.5 flanges due to its ability to seal at low
bolt loads. Style 905 gaskets meet the Fugitive Emissions requirements, have been fire
tested and approved according the requirements of the PVRC Fire Tightness Test
(FITT) procedure and have been sealbility tested per ROTT procedure. The PVRC
design gasket constants 905 Gaskets with Flexible Graphite covering layers are as
follows:
• Gb: 90 psi
• a: 0.547
• Gs: 0.388 psi
The gasket dimensions for ASME are shown in Appendix 9.4. The standard
material for the metal core is 316 Stainless Steel. Other alloys are available upon
request.
5.5.2. STYLE 905 GASKETS FOR HEAT EXCHANGERS
One of the most frequent uses of Style 905 Gaskets are in Shell and Tube Heat
Exchangers, due to their ability of to avoid mechanical shearing problems associated
other gasket types in heavy thermal cycling applications. The standard core material
is 316 Stainless Steel and the covering layer is Flexible Graphite. Other alloys are
available upon request. The gasket thickness before seating is 0.080 in (2 mm) and the
other dimensions, tolerances and shapes follow the indications of the Chapter 6 Section
6 of this book.
182
6. RING-JOINTS
Metallic Ring-Joints are produced according to the standards established by
the American Petroleum Institute (API) and the American Society of Mechanical
Engineers (ASME) for application at elevated temperatures and pressures. A typical
application of Ring-Joints is the “Christmas Trees” used in oil fields (Figure 9.8).
The seal is obtained in a line of contact by a wedge action with high seating
pressures thus, forcing the material to flow. The small sealing area with high contact
pressure results in great reliability. However the contact surfaces of the gasket and
the flange should be carefully finished. Some styles of Ring-Joints are pressure
activated, that is, the greater the pressure the better the sealability. Ring-Joints are
manufactured according the ASME B16.20 and API 6A standards.
Figure 9.8
183
6.1. MATERIALS
The materials should be forged or laminated. Cast materials should not be
used. The Table 9.2 shows the standard materials recommended by the ASME B16.20
for Ring-Joint gaskets.
Table 9.2
Ring-Joints Materials per ASME B16.20
Material
Soft Iron
Carbon Steel
AISI 502
AISI 410
AISI 304
AISI 316
AISI 347
Monel
Nickel
Copper
Maximum
Hardness
Brinell
90
120
130
170
160
160
160
125
120
-
Maximum
Hardness
Rockwell B
56
68
72
86
83
83
83
70
68
-
Maximum
Temperature
o
F (°°C )
538
538
649
704
Note 1
Note 1
Note 1
Note 1
Note 1
Note 1
Material
Code
D
S
F5
S410
S304
S306
S347
M
N
CU
Note1:
Maximum service temperature for styles 950 and 951. For styles BX and RX the
maximum is 250O F (121o C).
6.2. SURFACE FINISH
The gasket sealing surface finish has a maximum roughness of 63 µin Ra (1.6 µm Ra)
for styles 950, 951 and RX and a maximum of 32 µin Ra (0.8 µm Ra) for style BX.
6.3. HARDNESS
The maximum hardness for each gasket material is shown in Table 9.2.
It is recommended that the hardness of the gasket be always less than that of the
flange so as not to damage it. When the materials of the flange and the gasket are
similar, it is recommended to heat treat the gasket to produce a hardness at least 30 HB
less than the flange.
184
6.4. DIMENSIONS AND TOLERANCES
The following standards have the dimensions, tolerances and application
recommendations for Ring-Joints.
• ASME B16.5 – Steel Pipe-Line Flanges
• ASME B16.20 – Metallic Gaskets for Pipe Flanges
• ASME B16.47 – Steel Pipe-Line Flanges
• API 6A – Specification for Wellhead Equipment.
• API 6B – Specification for Wellhead Equipment.
• API 6D – Steel Gate, Plug, Ball and Check Valves for PipeLine Service.
Annexes 9.1, 9.2 and 9.3, at the end of this Chapter have the dimensions for
Ring-Joints per ASME B16.20.
6.5. STYLES
6.5.1. STYLE 950
Style 950, which is frequently referred to as the oval ring, was the gasket that was
initially standardized (Figure 9.9). Later developments resulted in other styles. If the
flange was designed using the older version of the gasket standard, for use with an
oval ring, then it should be used only with style 950 gaskets.
Figure 9.9
185
6.5.2. STYLE 951
Style 951 has an octagonal section as shown on Figure 9.10. Style 951 has
better sealing performance than Style 950 and its use is recommended for new
applications. For this style flanges are manufactured according to new issues of ASME
and API standards and have grooves with a profile designed to work with styles 950
and 951.
Figure 9.10
6.5.3. STYLE RX
Style RX (Figure 9.11) is a pressure-activated gasket. Its shape is designed to
use the fluid pressure to increase the sealability. The outside sealing surface of the
gasket makes the initial contact with the flange seating the gasket. As the internal
pressure of the piping or equipment is increased the contact pressure between gasket
and flange also increases due to the shape of the gasket. High seating pressures are
created increasing the sealability. This design characteristic makes this gasket style
more resistant to vibrations, pressure surges and shocks that occur during oil well
drilling. Style RX is interchangeable with style 950 and 951, using the same flange
grooving.
Figure 9.11
186
6.5.4. STYLE BX
Style BX gasket has a square cross section with bevelled corners as shown in
Figure 9.12. Designed for use only in flanges API 6BX. Style BX is recommended for
pressures from 5000 psi up to 20 000 psi. The average diameter of the gasket is slightly
greater than that of the flange groove. This way when the gasket is seated it stays precompressed by the outside diameter creating a high seating stress.
Figure 9.12
6.5.5. OTHER STYLES
There are several other styles of metallic gaskets such as the lens, delta and
Bridgeman styles, which are outside of the scope of this book due to their restricted
use in specific applications.
187
Annex 9.1
Dimensions for Styles 950 and 951 in inches
Ring
Number
Pitch
Diameter
Width of
Ring
R-11
R-12
R-13
R-14
R-15
R-16
R-17
R-18
R-19
R-20
R-21
R-22
R-23
R-24
R-25
R-26
R-27
R-28
R-29
R-30
R-31
R-32
R-33
R-34
1.344
1.563
1.688
1.750
1.875
2.000
2.250
2.375
2.563
2.688
2.844
3.250
3.250
3.750
4.000
4.000
4.250
4.375
4.500
4.625
4.875
5.000
5.188
5.188
0.250
0.313
0.313
0.313
0.313
0.313
0.313
0.313
0.313
0.313
0.438
0.313
0.438
0.438
0.313
0.438
0.438
0.500
0.313
0.438
0.438
0.500
0.313
0.438
Height of Ring
Oval
Octogonal
B
H
0.44
0.38
0.56
0.50
0.56
0.50
0.56
0.50
0.56
0.50
0.56
0.50
0.56
0.50
0.56
0.50
0.56
0.50
0.56
0.50
0.69
0.63
0.56
0.50
0.69
0.63
0.69
0.63
0.56
0.50
0.69
0.63
0.69
0.63
0.75
0.69
0.56
0.50
0.69
0.63
0.69
0.63
0.75
0.69
0.56
0.50
0.69
0.63
188
Radius
Width
Style 950
Style 951
R
0.170
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.206
0.06
0.305
0.06
0.206
0.06
0.305
0.06
0.305
0.06
0.206
0.06
0.305
0.06
0.305
0.06
0.341
0.06
0.206
0.06
0.305
0.06
0.305
0.06
0.341
0.06
0.206
0.06
0.305
0.06
Annex 9.1 (Continued)
Dimensions for Styles 950 and 951 in inches
Ring
Number
R-35
R-36
R-37
R-38
R-39
R-40
R-41
R-42
R-43
R-44
R-45
R-46
R-47
R-48
R-49
R-50
R-51
R-52
R-53
R-54
R-55
R-56
R-57
R-58
R-59
R-60
R-61
R-62
R-63
R-64
R-65
R-66
R-67
R-68
R-69
R-70
R-71
R-72
R-73
R-74
Pitch
Diameter
P
5.375
5.875
5.875
6.188
6.375
6.750
7.125
7.500
7.625
7.625
8.313
8.313
9.000
9.750
10.625
10.625
11.000
12.000
12.750
12.750
13.500
15.000
15.000
15.000
15.625
16.000
16.500
16.500
16.500
17.875
18.500
18.500
18.500
20.375
21.000
21.000
21.000
22.000
23.000
23.000
Width of
Ring
A
0.438
0.313
0.438
0.625
0.438
0.313
0.438
0.750
0.313
0.438
0.438
0.500
0.750
0.313
0.438
0.625
0.875
0.313
0.438
0.625
1.125
0.313
0.438
0.875
0.313
1.250
0.438
0.625
1.000
0.313
0.438
0.625
1.125
0.313
0.438
0.750
1.125
0.313
0.500
0.750
Height of Ring
Oval
Octogonal
B
H
0.69
0.63
0.56
0.50
0.69
0.63
0.88
0.81
0.69
0.63
0.56
0.50
0.69
0.63
1.00
0.94
0.56
0.50
0.69
0.63
0.69
0.63
0.75
0.69
1.00
0.94
0.56
0.50
0.69
0.63
0.88
0.81
1.13
1.06
0.56
0.50
0.69
0.63
0.88
0.81
1.44
1.38
0.56
0.50
0.69
0.63
1.13
1.06
0.56
0.50
1.56
1.50
0.69
0.63
0.88
0.81
1.31
1.25
0.56
0.50
0.69
0.63
0.88
0.81
1.44
1.38
0.56
0.50
0.69
0.63
1.00
0.94
1.44
1.38
0.56
0.50
0.75
0.69
1.00
0.94
189
Width
Radius
Style 951 Style 950
C
R
0.305
0.06
0.206
0.06
0.305
0.06
0.413
0.06
0.305
0.06
0.206
0.06
0.305
0.06
0.485
0.06
0.206
0.06
0.305
0.06
0.305
0.06
0.341
0.06
0.485
0.06
0.206
0.06
0.305
0.06
0.413
0.06
0.583
0.06
0.206
0.06
0.305
0.06
0.413
0.06
0.780
0.09
0.206
0.06
0.305
0.06
0.583
0.06
0.206
0.06
0.879
0.09
0.305
0.06
0.413
0.06
0.681
0.09
0.206
0.06
0.305
0.06
0.413
0.06
0.780
0.09
0.206
0.06
0.305
0.06
0.485
0.06
0.780
0.09
0.206
0.06
0.341
0.06
0.485
0.06
Annex 9.1 (Continued)
Dimensions for Styles 950 and 951 in inches
Ring
Number
R-74
R-75
R-76
R-77
R-78
R-79
R-80
R-81
R-82
R-84
R-85
R-86
R-87
R-88
R-89
R-90
R-91
R-92
R-93
R-94
R-95
R-96
R-97
R-98
R-99
R-100
R-101
R-102
R-103
R-104
R-105
Pitch
Diameter
P
23.000
23.000
26.500
27.250
27.250
27.250
24.250
25.000
2.250
2.500
3.125
3.563
3.938
4.875
4.500
6.125
10.250
9.000
29.500
31.500
33.750
36.000
38.000
40.250
9.250
29.500
31.500
33.750
36.000
38.000
40.250
Width of
Ring
A
0.750
1.250
0.313
0.625
1.000
1.375
0.313
0.563
0.438
0.438
0.500
0.625
0.625
0.750
0.750
0.875
1.250
0.438
0.750
0.750
0.750
0.875
0.875
0.875
0.438
1.125
1.250
1.250
1.250
1.375
1.375
Height of Ring
Oval
Octogonal
B
H
1.00
0.94
1.56
1.50
0.56
0.50
0.88
0.81
1.31
1.25
1.75
1.63
0.50
0.75
0.63
0.63
0.69
0.81
0.81
0.94
0.94
1.06
1.50
0.69
0.63
0.94
0.94
0.94
1.06
1.06
1.06
0.63
1.38
1.50
1.50
1.50
1.63
1.63
Width
Radius
Style 951 Style 950
C
R
0.485
0.06
0.879
0.09
0.206
0.06
0.413
0.06
0.681
0.09
0.977
0.09
0.206
0.06
0.377
0.06
0.305
0.06
0.305
0.06
0.341
0.06
0.413
0.06
0.413
0.06
0.485
0.06
0.485
0.06
0.583
0.06
0.879
0.09
0.305
0.06
0.485
0.06
0.485
0.06
0.485
0.06
0.583
0.06
0.583
0.06
0.583
0.06
0.305
0.06
0.780
0.09
0.879
0.09
0.879
0.09
0.879
0.09
0.977
0.09
0.977
0.09
Tolerances:
• Pitch Diameter P: ±0.007.
• Width of Ring A: ±0.007.
• Height B and H: +0.05,0-0.02. The variation in height along the Ring cannot
exceed 0.02.
• Width of Flat C: ±0.008.
• Radius R: ±0.02.
• Angle 23o : ± 0.5o.
190
Annex 9.1 (Continued)
Application Data for Styles 950 and 951
Ring
Number
R
R-11
R-12
R-13
R-14
R-15
R-16
R-17
R-18
R-19
R-20
R-21
R-22
R-23
R-24
R-25
R-26
R-27
R-28
R-29
R-30
R-31
R-32
R-33
R-34
R-35
R-36
R-37
R-38
R-39
R-40
R-41
R-42
R-43
R-44
R-45
R-46
R-47
R-48
R-49
R-50
R-51
R-52
R-53
R-54
R-55
R-56
R-57
R-58
150
Pressure Class and Nominal Diameter
ASME B16.5
ASME B16.47 Séries A
API 6B
300
300
900 1500 2500 720 2000 3000 5000 150
900
600
960
600
½
½
½
½
¾
¾
¾
1
1
1
1
¾
1
1
1
1
1¼
1¼
1¼
1
1¼
1¼
1¼
1¼
1½
1½
1½
1½
1½
1½
1½
2
2
2
2
2½
2½
1 ¼
1 ½
1¼
2
1½
2
2
2
2½
2½
2 ½
2
2½
2½
2½
2½
3
3
3
3
3
3
3
3
3 ½
3½
3
3
4
4
4
4
4
4
3½
4
4
4
5
5
5
5
5
5
6
6
6
5
6
5
5
6
6
6
6
6
8
8
8
8
8
8
8
8
8
10
10
10
10
10
10
10
10
10
12
12
12
12
12
191
12
12
12
12
Annex 9.1 (Continued)
Application Data for Styles 950 and 951
Ring
Number
R
R-59
R-60
R-61
R-62
R-63
R-64
R-65
R-66
R-67
R-68
R-69
R-70
R-71
R-72
R-73
R-74
R-75
R-76
R-77
R-78
R-79
R-80
R-81
R-82
R-84
R-85
R-86
R-87
R-88
R-89
R-90
R-91
R-92
R-93
R-94
R-95
R-96
R-97
R-98
R-99
R-100
R-101
R-102
R-103
R-104
R-105
150
Pressure Class and Nominal Diameter
ASME B16.5
ASME B16.47 Séries A
API 6B
300
300
900 1500 2500 720 2000 3000 5000 150
900
600
960
600
14
12
14
14
14
14
14
14
14
14
16
16
16
16
16
16
16
16
16
18
18
18
18
18
18
18
18
18
20
20
20
20
20
20
20
20
20
24
24
24
24
24
24
22
22
1
1½
2
2½
3
4
3½
5
10
26
28
30
32
34
36
8
8
26
28
30
32
34
36
192
Annex 9.2
Dimensions for Style RX in inches
Ring
Number
Outside
Diameter
OD
Width
A
Width
C
Height
CH
Height
H
Radius
R
Hole
D
RX-20
RX-23
RX-24
RX-25
RX-26
RX-27
RX-31
RX-35
RX-37
RX-39
RX-41
RX-44
RX-45
RX-46
RX-47
RX-49
RX-50
RX-53
RX-54
RX-57
RX-63
RX-65
RX-66
3.000
3.672
4.172
4.313
4.406
4.656
5.297
5.797
6.297
6.797
7.547
8.047
8.734
8.750
9.656
11.047
11.156
13.172
13.281
15.422
17.391
18.922
18.031
0.344
0.469
0.469
0.344
0.469
0.469
0.469
0.469
0.469
0.469
0.469
0.469
0.469
0.531
0.781
0.469
0.656
0.469
0.656
0.469
1.063
0.469
0.656
0.182
0.254
0.254
0.182
0.254
0.254
0.254
0.254
0.254
0.254
0.254
0.254
0.254
0.263
0.407
0.254
0.335
0.254
0.335
0.254
0.582
0.254
0.335
0.125
0.167
0.167
0.125
0.167
0.167
0.167
0.167
0.167
0.167
0.167
0.167
0.167
0.188
0.271
0.167
0.208
0.167
0.208
0.167
0.333
0.167
0.208
0.750
1.000
1.000
0.750
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.125
1.625
1.000
1.250
1.000
1.250
1.000
2.000
1.000
1.250
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.09
0.06
0.06
0.06
0.06
0.06
0.09
0.06
0.06
-
193
Annex 9.2 (Continued)
Dimensions for Style RX in inches
Ring
Number
Outside
Diameter
OD
Width
A
Width
C
Height
CH
Height
H
RX-69
RX-70
RX-73
RX-74
RX-82
RX-84
RX-85
RX-86
RX-87
RX-88
RX-89
RX-90
RX-91
RX-99
RX-201
RX-205
RX-210
RX-215
21.422
21.656
23.469
23.656
2.672
2.922
3.547
4.078
4.453
5.484
5.109
6.875
11.297
9.672
2.026
2.453
3.844
5.547
0.469
0.781
0.531
0.781
0.469
0.469
0.531
0.594
0.594
0.688
0.719
0.781
1.188
0.469
0.226
0.219
0.375
0.469
0.254
0.407
0.263
0.407
0.254
0.254
0.263
0.335
0.335
0.407
0.407
0.479
0.780
0.254
0.126
0.120
0.213
0.210
0.167
0.271
0.208
0.271
0.167
0.167
0.167
0.188
0.188
0.208
0.208
0.292
0.297
0.167
0.057
0.072 (2)
0.125 (2)
0.167 (2)
1.000
1.625
1.250
1.625
1.000
1.000
1.000
1.125
1.125
1.250
1.250
1.750
1.781
1.000
0.445
0.437
0.750
1.000
Hole
Radius
D
R
Note 1
0.06
0.09
0.06
0.09
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.09
0.09
0.06
0.02 (3)
0.02 (3)
0.03 (3)
0.06 (3)
0.06
0.06
0.06
0.09
0.09
0.12
0.12
0.12
0.12
-
Notes:
1. For Rings RX-82 to RX-91 only one hole is required
2. The Tolerance for these dimensions is +0, -0.015.
3. The Tolerance for these dimensions is +0.02, - 0.
Tolerances:
• Outside Diameter OD: +0.020, -0.
• Width A: +0.008, -0. The variation of the width cannot exceed 0.004 around
the ring.
• Width C: +0.006, -0.
• Height CH: +0, -0.03.
• Height H: +0.008, -0. The variation of the height cannot exceed 0.004 around
the ring..
• Radius R: ± 0.02.
• Angle de 23o : ± 0.5o.
Hole D: ±0.02.
194
Annex 9.2 (Continued)
Application Data for Style RX
RX Ring
Number
RX-20
RX-23
RX-24
RX-25
RX-26
RX-27
RX-31
RX-35
RX-37
RX-39
RX-41
RX-44
RX-45
RX-46
RX-47
RX-49
RX-50
RX-53
RX-54
RX-57
RX-63
RX-65
RX-66
RX-69
RX-70
RX-73
RX-74
RX-82
RX-84
RX-85
RX-86
RX-87
RX-88
RX-89
RX-90
RX-91
RX-99
RX-201
RX-205
RX-210
RX-215
Pressure Class and Nominal Diameter - API 6B
2900
720 - 960 - 2000
3000
5000
1½
1½
1½
2
2
2
3 1/8
2½
2½
2½
3
3
3
4
4
4
5
5
5
6
6
6
8
8
8
8
10
10
10
12
12
14
16
16
18
18
20
20
1
1½
2
2½
3
4
3½
5
10
8
8
1 3/8
1 13/16
2 9/16
4 1/16
195
Annex 9.3
Dimensions for Style BX in inches
Ring
Number
BX
BX-150
BX-151
BX-152
BX-153
BX-154
BX-155
BX-156
BX-157
BX-158
BX-159
BX-160
BX-161
BX-162
BX-163
BX-164
BX-165
BX-166
BX-167
BX-168
BX-169
BX-170
BX-171
BX-172
BX-303
Nominal
Diameter
Diameter
OD
Height
H
Width
A
1 11/16
1 13/16
2 1/16
2 9/16
3 1/16
4 1/16
7 1/16
9
11
13 5/8
13 5/8
16 5/8
16 5/8
18 3/4
18 3/4
21 1/4
21 1/4
26 3/4
26 3/4
5 1/8
6 5/8
8 9/16
11 5/32
30
2.842
3.008
3.334
3.974
4.600
5.825
9.367
11.593
13.860
16.800
15.850
19.347
18.720
21.896
22.463
24.595
25.198
29.896
30.128
6.831
8.584
10.529
13.113
33.573
0.366
0.379
0.403
0.448
0.488
0.560
0.733
0.826
0.911
1.012
0.938
1.105
0.560
1.185
1.185
1.261
1.261
1.412
1.412
0.624
0.560
0.560
0.560
1.494
0.366
0.379
0.403
0.448
0.488
0.560
0.733
0.826
0.911
1.012
0.541
0.638
0.560
0.684
0.968
0.728
1.029
0.516
0.632
0.509
0.560
0.560
0.560
0.668
196
Diameter Width
C
ODT
2.790
2.954
3.277
3.910
4.531
5.746
9.263
11.476
13.731
16.657
15.717
19.191
18.641
21.728
22.295
24.417
25.020
29.696
29.928
6.743
8.505
10.450
13.034
33.361
0.314
0.325
0.346
0.385
0.419
0.481
0.629
0.709
0.782
0.869
0.408
0.482
0.481
0.516
0.800
0.550
0.851
0.316
0.432
0.421
0.481
0.481
0.481
0.457
Hole
D
(1)
0.06
0.06
0.06
0.06
0.06
0.06
0.12
0.12
0.12
0.12
0.12
0.12
0.06
0.12
0.12
0.12
0.12
0.06
0.06
0.06
0.06
0.06
0.06
0.06
Annex 9.3 (Continued)
Dimensions for Style BX in inches
1. For all Rings only one hole is required.
Tolerances:
• Outside Diameter OD: +0, -0.005.
• Height H: +0.008, -0. . The variation of the height cannot exceed 0.004 around the ring.
• Width A: +0.008, -0. . The variation of the width cannot exceed 0.004 around the ring.
• Diameter ODT: ± 0.002.
• Width C: +0.006, -0.
• Hole D: ±0.02.
• Height CH: +0, -0.03.
• Radius R: de 8% a 12% of Ring height H.
Angle 23o : ± 0.25o.
Application Data for BX Rings
BX Ring
Number
BX-150
BX-151
BX-152
BX-153
BX-154
BX-155
BX-156
BX-157
BX-158
BX-159
BX-160
BX-161
BX-162
BX-163
BX-164
BX-165
BX-166
BX-167
BX-168
BX-169
BX-170
BX-171
BX-172
BX-303
2 000
Pressure Class and Nominal Diameter - API 6BX
3 000
5 000
10 000
15 000
1 11/16
1 11/16
13
1 13/16
1 /16
1
2 1/16
2 /16
9
2 9/16
2 /16
1
3 1/16
3 /16
1
4 1/16
4 /16
1
7 1/16
7 /16
9
9
11
11
13 5/8
13 5/8
5
13 /8
16 ¾
16 ¾
16 ¾
16 ¾
18 ¾
18 ¾
18 ¾
21 1/4
21 1/4
26 ¾
26 ¾
5 1/8
6 5/8
8 9/16
11 5/32
30
30
197
6 5/8
8 9/16
11 5/32
20 000
1 13/16
2 1/16
2 9/16
3 1/16
4 1/16
7 1/16
9
11
13 5/8
Annex 9.4
Style 920 Gasket Dimensions for for ASME B16.5 Flanges in inches
NPS
(in)
Gasket
Inside
Diameter
(in)
1/2
0.84
1.88
3/4
1.06
1
Gasket Outside Diameter (in)
150
1500
2500
2.50
2.50
2.75
2.63
2.75
2.75
3.00
2.88
2.88
3.13
3.13
3.38
3.25
3.25
3.25
3.50
3.50
4.13
3.38
3.75
3.75
3.75
3.88
3.88
4.63
2.38
4.13
4.38
4.38
4.38
5.63
5.63
5.75
2 1/2
2.88
4.88
5.13
5.13
5.13
6.50
6.50
6.63
3
3.50
5.38
5.88
5.88
5.88
6.63
6.88
7.75
3 1/2
4.00
8.50
9.00
4
4.50
6.88
7.13
7.00
7.63
8.13
8.25
9.25
5
5.56
7.75
8.50
8.38
9.50
9.75
10.00
11.00
6
6.62
8.75
9.88
9.75
10.50
11.38
11.13
12.50
8
8.62
11.00
12.13
12.00
12.63
14.13
13.88
15.25
10
10.75
13.38
14.25
14.13
15.75
17.13
17.13
18.75
12
12.75
16.13
16.63
16.50
18.00
19.63
20.50
21.63
14
14.00
17.75
19.13
19.00
19.38
20.50
22.75
16
16.00
20.25
21.25
21.13
22.25
22.63
25.25
18
18.00
21.63
23.50
23.38
24.13
25.13
27.75
20
20.00
23.88
25.75
25.50
26.88
27.50
29.75
24
24.00
28.25
30.50
30.25
31.13
33.00
35.50
300
400
600
2.13
2.13
2.13
2.25
2.63
2.63
1.31
2.63
2.88
1 1/4
1.66
3.00
1 1/2
1.91
2
198
900
CHAPTER
10
CAMPROFILE GASKETS
1. INTRODUCTION
With the continuous advance of the chemical and petrochemical processes, it
is necessary to have gaskets for higher pressures and temperatures, especially for
Shell and Tube Heat Exchangers. The most used gasket type for this equipment is the
Double Jacketed, Teadit Style 923, which is a soft filler with a metallic jacket, as shown
in Figure 8.6.
One of the characteristics of gaskets for Heat Exchangers is that they are
manufactured according to the dimensions of each equipment. There are no
dimensional standards or shapes.
To be used in a high pressure application a gasket must be able to resist high
seating stress, assuring the sealability. The Double Jacketed Gaskets, due to their
design, with a soft core, are capable of filling up the flange irregularities. However,
because of the soft core, they are not recommended for applications where the seating
stress is higher than 250 MPa (36,000 psi).
For applications that require high seating stresses, flat metal gaskets like the
Teadit Style 940 (Figure 9.2) can be used. These gaskets have several manufacturing
and installation difficulties. They are very sensitive to any flange irregularity especially
scratches, pitting or tool marks. Being made from a solid metal or alloy, it is very
difficult to seat and fill up the normal flange irregularities. Due to the large dimensions,
some gaskets are larger than the available sheet stock, it becomes necessary to weld,
and areas of higher hardness are created during the welding process, making it more
difficult to seat the gasket, or damage the flanges.
199
To avoid the flat metal gasket problems, the alternative is to use serrated
metal gaskets, Teadit Style 941, as shown in Figure 9.3, which have the same high
pressure capabilities. The serrated sealing surface creates a high seating stress and
additionally a labyrinth effect. However, the serrated surface, desirable to create a
good seal, can damage the flange surface with circumferential marks.
The Camprofile Gaskets, Teadit Style 942, combine the pressure resistance of
flat metal gaskets with the excellent sealability of the Flexible Graphite (Graflex) or
Expanded PTFE tape (24BB). They have a serrated metal core covered on both sides
with a thin tape of Flexible Graphite or Expanded PTFE, as shown in Figure 10.1.
GRAFLEX OR PTFE TAPE
Figure 10.1
The Teadit Camprofile gaskets have the following characteristics:
• Operating pressure up to 3,700 psi (250 bar).
• Maximum temperature up to 1100o F (600o C).
• Wide range of service.
• Less susceptible to flange imperfections than conventional flat metal
gaskets.
The serrated metal core produces a high seating stress with a low torque. The
thin Flexible Graphite or Expanded PTFE core fills up the flange irregularities and
prevents the serrated finish from damaging the flanges.
2. MATERIALS
2.1. METALLIC CORE
The core material should be chemically and thermally compatible with the
fluid to be sealed. If possible the core metal should be the same as used to manufacture
the flanges to avoid corrosion or differential Thermal Expansion. It is recommended
that the design should follow the recommendations of Chapters 2 and 6 of this book.
200
2.2. SEALING COVER
The most widely used cover material is the Graflex® - Flexible Graphite. For
operational conditions where the Flexible Graphite is not recommended the 24BB
Expanded PTFE tape is used. The Table 10.1 shows the Temperature and Pressure
limits for the cover materials.
Table 10.1
Cover Materials Temperature and Pressure Limits
Material
Graflex®
24BB
Temperature - oF (oC)
min
max
-400 (-240)
-400 (-240)
1200 (650)
520 (270)
Pressure – psi (bar)
3700 (250)
1500 (100)
3. PRESSURE AND TEMPERATURE LIMITS
The Pressure and Temperature range is related to the range of each
component, as indicated in Chapter 6 and Table 10.1. The Service Range is the
combination of the limit for the metal and cover limits. For example a Teadit Camprofile
Style 942 with a Carbon Steel core and Graflex® cover has the following limits:
• Maximum pressure: 3700 psi (250 bar).
• Temperature range F o (oC): -40 to 1200 (-40 to 650)
4. BOLTING CALCULATION
The “m” and “y” values for ASME Code calculation are shown in Table 10.2
and the values for DIN Standard calculation are in Table 10.3.
Table 10.2.
ASME Gasket Factors
m
3.25
3.50
3.50
3.75
3.75
4.25
Material
Aluminum
Copper
Brass
Carbon Steel
Monel
Stainless Steel
201
y
5500
6500
6500
7600
9000
10100
Table 10.3
DIN Gasket Calculation
Material
Alumínio
Cobre
Níquel
AISI 1006/1008
AISI 304/316
AISI 321
AISI 309
Gasket Installation
Factor Seating Stress
- MPa m
1.1
1.1
1.1
1.1
1.1
1.1
1.1
Mín.
σ VU
20
20
20
20
20
20
20
Máx.
σ VO
140
300
510
500
500
500
600
Maximum Operating Stress - MPa
100
200
300
120
270
500
500
500
500
570
93
195
490
495
450
450
530
150
480
315
420
420
500
400
500
600
350
400
240
240
390
460
It is recommended that after the calculations per ASME Code, to verify if the
Maximum Seating and Operational Stress are lower are indicated in Table 10.3 to avoid
crushing the gasket.
5. SURFACE FINISH
The recommended Surface Finish for the flange sealing surfaces is 63 to 80 µin
(1.6 µm a 2.0 µm) Ra. This finish range is known as “smooth finish”.
6. DESIGN AND MANUFACTURING TOLERANCES
The Table 10.4 shows the design recommendations and the Table 10.5 shows
the manufacturing tolerance for Teadit Style 942 gaskets.
Table 10.4
Gasket Design
Type of Flange
Gasket Diameter
Inside
Outside
Tongue and Groove
Groove inside diameter
plus 1/16" (1.6mm)
Groove outside diameter
less 1/16" (1.6mm)
Gaskets confined by
the outside diameter
Flange inside diameter
plus 1/8" (3.2 mm)
Flange outside diameter
less 1/16" (1.6 mm)
Gaskets confined by
the inside diameter
Flange inside diameter
plus 1/16" (1.6 mm)
Flange outside diameter
less 1/8" (3.2 mm)
202
Table 10.5
Manufacturing Tolerances
Gasket Inside
Diameter - in (mm)
Tolerance - in (mm)
Inside
Outside
Up to 20 (500)
+1/32, 0.0 (+0.8 -0.0)
+0.0, -1/32 (+0.0 -0.8)
From 20 (500) to 60 (1500)
+1/16, -0.0 (+1.6 -0.0)
+0.0, -1/16 (+0.0 -1.6)
Larger than 60 (1500)
+3/32, -0.0 (+2.5 -0.0)
+0.0, -3/32 (+0.0 -2.5)
7. SHAPES
The Annex 8.1 shows the most used shapes for Heat Exchanger gaskets. The
partitions are welded to the gasket inside perimeter.
The standard gasket widths (“B” dimension) are 3/8", 1/2", 5/8" and 3/4" (10, 13, 16
and 20 mm).
The standard thickness (dimension “E”) is 5/32" ± 1/128" (4 ±0.2 mm), the
metallic core is 1/8" (3.2 mm) and 1/64" (0.4mm) each non-metallic cover.
8. CAMPROFILE GASKETS FOR ASME B16.5 FLANGES
At the time of this edition there is no current standard for Camprofile gaskest
for ASME B16.5 flanges. Several gasket organizations are working towards this goal.
The most commercialy available configuration is shown in Figure 10.2. The
metallic Sealing Ring is covered with Flexible Graphite or PTFE with a thinner metallic
Centering Ring.
Figura 10.2
203
9. DIMENSIONS NAD TOLERANCES
Gasket Dimensions for ASME B16.5 flanges are shown in Table 10.6 and
Annex 10.1.
Table 10.6
Camprofile Gasket Dimensions
Dimensions (inches)
Characteristic
Minimuum
0.115
0.024
0.015
0.030
Sealing Ring Thickness
Centering Ring Thickness
Cover Thickness
Serrations Depth
Maximum
0.131
0.035
0.030
0.060
9.1. IDENTIFICATION
The centering ring is permanently marked with lettering at least 1/8 in (3.2 mm)
height with the following information:
• Manufacturer’s name or trademark.
• Flange size (NPS).
• Pressure class.
• Sealing Ring metal abbreviation.
• Cover material abbreviation.
• Centering Ring metal abbreviation.
The material code abbreviations are shown in Annex 10.2.
204
Annex 10.1
Camprofile Gasket Dimensions for ASME B16.5 flanges
Sealing Ring
ND
(in)
Outside
Inside
D i a m e t e r Diameter
(in)
(in)
Centering Ring Outside Diameter by Pressure Class (in)
150
300
400
600
900
1500
2500
1/2
0.91
1.31
1.88
2.13
2.13
2.13
2.50
2.50
2.75
3/4
1.13
1.56
2.25
2.63
2.63
2.63
2.75
2.75
3.00
1
1.44
1.87
2.63
2.88
2.88
2.88
3.13
3.13
3.38
1 1/4
1.75
2.37
3.00
3.25
3.25
3.25
3.50
3.50
4.13
1 1/2
2.06
2.75
3.38
3.75
3.75
3.75
3.88
3.88
4.63
2
2.75
3.50
4.13
4.38
4.38
4.38
5.63
5.63
5.75
2 1/2
3.25
4.00
4.88
5.13
5.13
5.13
6.50
6.50
6.63
3
3.87
4.88
5.38
5.88
5.88
5.88
6.63
6.88
7.75
4
4.87
6.06
6.88
7.13
7.00
7.63
8.13
8.25
9.25
5
5.94
7.19
7.75
8.50
8.38
9.50
9.75
10.00
11.00
6
7.00
8.37
8.75
9.88
9.75
10.50
11.38
11.13
12.50
8
9.00
10.50
11.00
12.13
12.00
12.63
14.13
13.88
15.25
10
11.13
12.63
13.38
14.25
14.13
15.75
17.13
17.13
18.75
12
13.37
14.87
16.13
16.63
16.50
18.00
19.63
20.50
21.63
14
14.63
16.13
17.75
19.13
19.00
19.38
20.50
22.75
-
16
16.63
18.38
20.25
21.25
21.13
22.25
22.63
25.25
-
18
18.87
20.87
21.63
23.50
23.38
24.13
25.13
27.75
-
20
20.87
22.87
23.88
25.75
25.50
26.88
27.50
29.75
-
24
24.88
26.87
28.25
30.50
30.25
31.13
33.00
35.50
-
Tolerances:
• Sealing Ring Inside Diameter:
o DN ½” to DN 8": ± 0.03 in
o DN 10" to DN 24": ± 0.06 in
• Sealing Ring Outside Diameter:
o DN ½” a DN 8": ± 0.03 in
o DN 10" a DN 24": ± 0.06 in
• Centering Ring Outside Diameter: ± 0.06 in
205
Anexo 10.2
Códigos dos materiais para Juntas Camprofile para flanges ASME B16.5
Material
Abbreviation
Sealing and Centering Rings
Carbon Steel
CRS
304 SS
304
304 L SS
304 L
309 SS
309
310 SS
310
316 L SS
316 L
317 L SS
317 L
347 SS
347
321 SS
321
430 SS
430
Monel 400
MON
Nickel 200
NI
Titanium
TI
20Cb-3 alloy
A-20
Hastelloy B
HAST B
Hastelloy C
HAST C
Inconel 600
INC 600
Inconel 625
INC 625
Inconel X-750
INX
Incoloy 800
IN 800
Incoloy 825
IN 825
Cover
Graflex - Flexible Graphite
FG
PTFE
PTFE
206
CHAPTER
11
GASKETS FOR
ELECTRICAL INSULATION
1. ELETROCHEMICAL CORROSION
This is the most frequently found type of corrosion. It occurs at room
temperature. It is the result of a reaction of two metals in contact in an aqueous
solution of salts, acids or alkalis. The Figure 11.1 illustrates electrochemical corrosion.
As can be observed, two reactions take place, one at the anode, the other at
the cathode. Anodic reactions are always oxidation and tend to dissolve the metal of
the anode or combine it to form an oxide.
The electrons produced in the anodic reaction participate in the cathodic
reaction. These electrons flow across the metal as an electrical current.
The cathodic reactions are always reductions and normally do not affect the
metal of the cathode, as the majority of the metals cannot be further reduced.
The basis of electrochemical corrosion is the existence of an anodic reaction
where the metal of the anode gives up electrons. The measurement of the tendency of
the metal to give up electrons serves as a basic criterion of corrodibility. This
measurement, expressed in volts in relation to a gaseous hydrogen cell is found in
corrosion manuals.
For Iron the value is 0.44 volts and for Zinc it is 0.76 volts. There is an
electrical current from Zinc to Iron, from the higher potential to the lower. Zinc is the
anode and is corroded.
If for example in place of Zinc in Figure 11.1 we had Copper, of 0.34 volt
potential, we would have corrosion of the iron that has a greater potential.
This way the relation between the electrochemical potentials of metals in contact with
each other is what is going to determine which of them will be corroded. The principle
207
is extensively used and the Zinc plating of carbon steel is one of the most common
examples of the controlled use of electrochemical corrosion.
The Table 11.1 shows the relationship between some metals and alloys.
Table 11.1
Electrolytic Series in Salt Water
Anode (base)
Magnesium
Zinc
Cast Iron
Carbon Steel
304 Stainless Steel
Copper
316 Stainless Steel
Inconel
Titanium
Monel
Gold
Platinum
Cathode (noble)
208
2. CATHODIC PROTECTION
Cathodic protection consists of the controlled use of the electrochemical
corrosion to protect pipelines, tanks and other submerged equipment. Piping or
equipment to be protected should be electrically insulated from the rest of the system
to prevent the flow of galvanic current to a non-protected area.
Zinc anodes are installed in sufficient quantities to absorb the galvanic current.
These anodes are consumed in the process and should be replaced periodically.
The Figure 11.2 illustrates a submerged pipeline protected by a Zinc electrode
insulated from the rest of the system.
Figure 11.2
3. INSULATION SYSTEM FOR FLANGES
Insulation gasket sets are used to insulate the protected area from electrical
contact. Figure 11.3 shows an insulating gasket style E. The components of an
insulation gasket set are:
• Gasket made of an insulating material.
• Insulating sleeves.
• Insulating washers.
The gaskets are dimensioned to be used with ASME B16.5 flanges.
As shown, to prevent electrical currents, which can cause corrosion, the
protected section, must be electrical insulated from the rest of the system.
209
Gasket materials:
• Phenolic Resin reinforced with cotton fabric 1/8" (3.2 mm) thick or Phenolic Resin
0.8" (2 mm) with a 0.02" (0.5 mm) Neoprene coating on each side.
• Compressed Sheet Packing.
3.1. INSULATION GASKETS STYLE E
It has the same outside diameter as the flange to prevent any foreign material
from penetrating between the flanges and making electrical contact. The Figure 11.3
shows a typical system for style E gasket.
Figure 11.3
210
3.2. INSULATION GASKETS STYLE F
It is designed in such a way that its external diameter touches the protection
sleeves of the bolts. They are more economic than style E. It is necessary to protect
the flanges adequately whenever there is a risk of foreign material penetrating between
them. Figure 11.4 shows a typical system with gasket style F.
Figure 11.4
3.3. GASKETS STYLES RJD 950 AND 951
The style 950 and 951 insulation gaskets are manufactured for use in flanges
for Ring-Joints. The style RJD 950 has an oval shape and the style RJD 951 an octagonal
shape. The gasket dimensions are according the ASME B16.20. It is necessary to
211
adequately protect the flanges whenever there is a risk of foreign materials penetrating
between them. Figure 11.5 shows a typical system with gasket type RJD style 950.
Gasket material: reinforced phenolic resin
3.4. INSULATION SLEEVES
The insulation sleeves can be manufactured with phenolic resin, polyethylene
or polypropylene plastic. The physical properties of the material for phenolic resin
insulation sleeves are the same as for the gasket. Plastic sleeves are highly flexible
and adequate for use in locations of high humidity as they have low water absorption.
The insulation sleeve thickness is 1/32 in (0.8 mm).
212
3.5. INSULATION WASHERS
The insulation washers are manufactured with phenolic resin reinforced with
cotton cloth. They have the same physical characteristics as the phenolic resin gaskets.
Standard thickness is 1/8 in (3.2 mm).
3.6. STEEL WASHERS
To protect the insulation washers against damage steel washers are installed
between them and the nut or the bolt head. The steel washers are manufactured with
electro-plated carbon steel 1/8 in (3.2 mm) thick.
4. SPECIFICATIONS FOR THE GASKET MATERIAL
Material: phenolic resin reinforced with cotton fabric.
Characteristics:
•
•
•
•
•
•
•
•
Dielectric strength ........................... parallel: 5KV/mm perpendicular: 3KV/mm
Resistance to compression ............. 1800 kgf/cm2
Bending strength ............................. 1000 kgf/cm2
Tensile strength ............................... 900 kgf/cm2
Water absorption ............................. 2,40%
Density ............................................. 1,30 g/cm3
Hardness Rockwell M ..................... 103
Maximum temperature ..................... 266o F (130o C)
213
214
CHAPTER
12
INSTALLATION AND
FUGITIVE EMISSIONS
1. INSTALLATION PROCEDURE
To obtain a satisfactory seal, it is necessary that basic procedures be followed
during the gasket installation. These procedures are of fundamental importance for a
successful operation no matter what style of gasket or material used.
a) Inspect the flange-sealing surface. Check for tool marks, dents, scratches
or corrosion. Radial tool marks on the sealing surface are difficult to seal regardless of
the style of gasket. Be sure that the flange finish is adequate for the style of gasket
being used.
b) Inspect the gasket. Verify to be sure that the gasket material is compatible
with the intended service. Check for defects and shipping or storage damage.
c) Inspect and clean bolts, nuts and washers.
d) Lubricate bolt threads and the nut contact surfaces. Do not install bolts
and nuts without lubrication. The lubricant should be compatible with the service
temperature. A good lubricant will provide a better application of the torque and,
consequently, higher precision of the Bolt Load.
e) For Raised Face or Flat Faced flanges installed vertically, start installation
by bolts on the lower part. Install the gasket then the other bolts.
f) For Male and Female or Tongue and Groove flanges, the gasket should be
installed in the center of the groove.
g) Install the bolts and hand tighten them in a cross pattern sequence as
shown in Annex 12.1. Number the bolts to facilitate the tightening order.
215
h) Tighten the bolts approximately 30% of the final torque following the cross
pattern sequence. If the correct tightening sequence is not followed, the flanges can
be misaligned, making it impossible to have uniform seating of the gasket.
i) Repeat step g, elevating the torque to 60% of the final value.
j) Continue tightening in clockwise sequence until the final value is reached.
The same bolt normally has to be tightened several times since as the nearest bolts are
tightened it loses its force. It is recommended that each bolt be tightened with the
final torque value at least 5 times.
k) All gaskets relax after seating. Retightening is recommended at least four
hous after the installation to compensate for relaxation, following the rotational
clockwise pattern.
l) Compressed Non-Asbestos Gaskets should not be retightened after they
have been exposed to high temperatures.
m) All retightening should be performed at ambient temperature and
atmospheric pressure.
2. TORQUE VALUES
The most precise method for obtaining the desired Seating Stress is to apply
the Bolt Load by measuring its tension. However, in practice, this procedure is
cumbersome and of difficult execution. If direct tension measuring is not possible it is
recommended to use hydraulic tools or a torque wrench. The use of manual tools
without torque control is acceptable only in non-critical applications.
Methods to calculate the Bolt Load and the torque values have been shown
in Chapter 2 of this book.
3. ALLOWABLE BOLT STRESS
The ASME Pressure Vessel and Boiler Code, Section VIII, Appendix S deals
with the bolt stress. For example, the designer of the flange should determine the
necessary tightening for the temperature and pressure in the specific operational
conditions, according to the allowable bolt stress at the operating temperature.
Hydrostatic testing, which in the majority of cases is necessary to verify the
system, is done at one and one half times the design pressure. Consequently, a flanged
joint designed in accordance with the ASME Code, which should be hydrostatic tested
with a pressure higher than the design pressure, has to be tightened for the test
conditions.
The ASME Pressure Vessel and Boiler Code, Section VIII, Appendix S
establishes that in order to pass the hydrostatic test, the bolts must be tightened up
to the torque necessary for that purpose. If, in this case, the tension is greater than
what is admissible, bolts made with a higher allowable tension material should be
used observing the following procedure:
216
• Use bolts with allowable tension compatible with the one necessary to
pass the hydrostatic test, following the normal installation procedure for
the gasket.
• After the hydrostatic test is completed, loosen the bolts approximately
50% of the initial tension.
• Replace the bolts used for the test with the originally designed bolts, one
at a time, tightening until reaching the torque of the other bolts.
• After replacing all bolts, tighten them up to the design torque following the
cross pattern sequence.
4. LEAKAGE
One of the most efficient ways to analyze the causes of a leakage is to carefully
analyze the gasket used when such a leakage has taken place as shown below:
• A very corroded gasket: select a material with a better corrosion resistance.
• A very extruded gasket: select a material with a better cold flow resistance
or with a higher seating stress, use a compression limit ring or redesign the
flanges.
• Gasket with a damaged sealing surface: verify the gasket and flange
dimensions. It could be that the gasket has the inside diameter smaller than
the inside diameter of the flange or the outside diameter of the gasket is
larger than the outside diameter of the flange.
• Gasket not seated: select a softer gasket material or reduce the contact area
between gasket and flange.
• Gasket thinner at the outside diameter: indication of a “rotation” or flange
deflection. Change the gasket dimensions in a way that it fits closer to the
bolts to reduce rotational torque. Select a softer gasket that requires a
lower seating stress. Reduce the area of the gasket. Reinforce the flange to
increase its rigidity.
• Gasket irregularly seated: incorrect procedure in tightening the bolts. Make
sure the tightening sequence of the bolts is followed properly.
• Gasket with regularly varying thickness: indication of flanges with excessive
distance between bolts or without sufficient rigidity. Reinforce the flanges,
reduce the distance between bolts or select a softer gasket.
5. MISALIGNED FLANGES
When the flanges are not aligned it is not recommended to align them by
tightening the bolts. Misalignments must be corrected prior to the gasket installation.
Spacers can be used to correct the misalignment as shown in Figure 12.1
217
Figure 12.1
6. LIVE LOADING
Just after the gasket seating, the process of Stress Relaxation starts, which is
the loss of the Bolt Load. The Relaxation process is a characteristic of flanged joints
and occurs with any kind of gasket.
The Relaxation is due to several factors as follows:
• Gasket Relaxation: gaskets are designed to, when seated, fill up the flange
irregularities. As this plastic deformation occurs the flanges get closer,
reducing the Bolt Load. The amount of this deformation depends upon the
gasket style and the operating temperature.
• Bolt Thread Relaxation: when tightened there is a contact between its parts.
There are microscopic points where the stress is higher than the Yield Stress for
their materials. With time, the material flows at these points, reducing the stress.
Studies have shown a reduction of 5% to 10% of the initial stress.
• Relaxation with temperature: bolts used in high temperature have the
tendency to relax with temperature and time. The amount of the relaxation
depends upon the temperature and the time.
• Vibration: under vibration bolts tend to relax. The total loss of the tightening
can occur at severe vibration condition.
218
• Cross Tightening: normally the tightening follows the cross pattern
procedure. When one bolt is tightened the nearest ones lose stress. If
simultaneous hydraulic tools are used to install the gasket this problem is
reduced.
• Thermal Expansion: when the temperature changes from room to operating,
there are several thermal expansions. As the flanges and the gaskets are
closer to the heat source than the bolts there are thermal and consequently
expansion gradients. The same problem occurs when the system is turned
off. These thermal changes relax the flanged joint.
• Thermal Cycle: when the system operates with thermal cycle or is frequently
turned off, the relaxation due to the thermal changes is greater.
To compensate for the loss of stress due to the Relaxation, the system
elasticity has to be increased. This can be achieved with longer bolts and sleeves or
with spring washers, as shown in Figure 12.2.
The use of longer bolts and sleeves is not recommended since to be effective
is necessary to have very long bolts, which is not always possible.
The most common system is the use of spring washers, known as Live Loading
or Constant Load.
Figure 12.2
6.1. LIVE LOADING
To compensate for the Relaxation, Teadit has developed the Live Loading
System of spring washers specially designed for use in flange applications, as shown
in Figure 12.3.
219
Figure 12.3
Before deciding to use a Live Loading System it is necessary to study the
need for it. It increases the installation costs and should be used only when needed.
The Live Loading System does not solve sealing problems, however, as it
maintains the Bolt Load, it reduces problems in critical applications.
Live Loading is recommended for the following conditions:
•
•
•
•
•
•
Products that can cause extensive environmental damage or loss of lives.
Systems with thermal cycling or operating temperature fluctuations.
When the ratio of the bolt length to its diameter is less than three.
Systems with vibrations.
When the gasket or flange materials have a high tendency to relaxation.
When there is a history of system leakage.
The Teadit Live Loading System is available for three levels of bolt stress as
shown in Annex 12.1. When tightened with the torque shown the bolt achieves the
stress level of 414 MPa (60,000 psi), 310 MPa (45,000 psi) or 207 MPa (30,000 psi). The
Bolt Load at this stress level is also shown.
The Spring Washers are manufactured with alloy steel ASTM A681 type H13,
oil finish for use with carbon steel bolts. The recommended temperature is from room
to 1100o F (590o C).
For corrosive applications the Spring Washers can also be manufactured
with Stainless Steel ASTM A693 type 17-P7 for temperatures of – 400 o F (–240 o C) to
220
550o F (290o C). Can also be manufactured with Inconel 718 (ASTM B637) for
temperatures – 400o F (-240o C) to 1100o F (590o C).
The gaskets are installed as shown in Figure 12.3, with one spring on each
side of the flange. The spring must have its higher side towards the bolt as indicated;
if it is not installed in this way the Bolt Load can be lower than indicated. When the
torque is achieved the spring will be flat.
For equipment such as Heat Exchangers, that operate under thermal cycle
more than one spring on each side may be needed. Please consult with Teadit for
these applications.
7. FUGITIVE EMISSIONS
To assure the life of future generations it has become necessary to reduce the
pollutants released into the environment. Additionally the loss of chemical products
into the environment is a cost to the industry.
The great majority of pollutants like the Oxides of Carbon, Nitrogen and Sulfur
are the result of burning of fossil fuels or the evaporation of Hydrocarbons. Their
emissions are part of the industrial process and are subject to specific controls.
However, there are undesirable losses in pump shafts, valve stems and flanges,
which in normal condition should not happen. These losses are known as Fugitive
Emissions. It has been estimated that in the USA, the Fugitive Emissions are in the
order of 300,000 tons per year. Most of the time it is necessary to have special equipment
to detect them.
The control of the Fugitive Emissions is also a benefit to the plant safety.
Non detected leaks are a major cause of fire and explosions in plants and oil refineries.
The USA was one of the first countries to control Fugitive Emissions with the
1990 Clean Air Act (CAA), which was a cooperation between the industry and the
Environmental Protection Agency (EPA). The CAA defined the list of Volatile Hazardous
Air Pollutants (VHAP). If any product has more than 5% of a VHAP in its composition
it has to be controlled.
To monitor the Fugitive Emissions the EPA has published the Reference
Method 21, which uses an Organic Vapor Analyzer (OVA). This equipment, calibrated
for Methane, measures the concentration in parts per million (ppm) of the product.
The OVA, pumps the gas through a sensor to determine its concentration.
Flanges, valve stems, pump and agitator’s shafts and any other equipment
that can cause a leak are subject to monitoring. For flanges, the maximum concentration,
measured according to the EPA Method 21 is 500 ppm. There has been a trend towards
reducing this value to 100 ppm.
For flanges, a first measurement must be done at about 1 meter (1 yard) from
the source, in a direction against the prevailing wind. Then at about 1 centimeter
(1/2 in) going around it. The value to be taken is the difference between the initial
value and the highest value closer to the flange. If the difference is higher than 500
ppm the flange is considered as leaking and must be repaired.
221
The EPA Method 21 is a “go-no go” kind of measurement, it determines if the
flange is leaking or not. However, it does not give a quantitative value of the leaking.
To obtain a quantitative value the equipment must be encapsulated, which is
costly and not always possible.
The EPA has developed several studies to correlate the value in ppm and the
flow per unit of time. The Chemical Manufactures Association (CMA) and the Society
of Tribologists and Lubrication Engineers have also done studies and arrived at similar
results. The leakage in grams per hour can be established as:
Leakage = 0.02784 (SV 0.733) g / hour
Where SV is the value measured in parts per million.
The value obtained by this equation gives an approximate quantity of the
product being released to the environment. For example if there is a leakage of 5,000
ppm we have:
Leakage = 0.02784 (SV 0.733) = 0.02784 (50000.733) = 14.322 g / hour
222
Annex 12.1
Tightening Sequence
223
224
Annex 12.2
Teadit Live Loading System
Bolt Nominal
Diameter
inches
1/2
5/8
3/4
7/8
1
1 1/8
1 1/4
1 3/8
1 1/2
1 5/8
1 3/4
1 7/8
2
2 1/4
2 1/2
2 3/4
3
A - mm
Teadit
Part Number
Free
ACX00008060
ACX00008045
ACX00008030
ACX00010060
ACX00010045
ACX00010030
ACX00012060
ACX00012045
ACX00012030
ACX00014060
ACX00014045
ACX00014030
ACX00016060
ACX00016045
ACX00016030
ACX00018060
ACX00018045
ACX00018030
ACX00020060
ACX00020045
ACX00020030
ACX00022060
ACX00022045
ACX00022030
ACX00024060
ACX00024045
ACX00024030
ACX00026060
ACX00026045
ACX00026030
ACX00028060
ACX00028045
ACX00028060
ACX00030060
ACX00030045
ACX00030030
ACX00032060
ACX00032045
ACX00032030
ACX00036060
ACX00036045
ACX00036060
ACX00040060
ACX00040045
ACX00040030
ACX00044060
ACX00044045
ACX00044030
ACX00048060
ACX00048045
ACX00048030
6.7
3.9
3.4
5.4
4.7
4.0
6.5
5.7
4.8
7.6
6.7
5.7
8.7
7.7
6.5
9.9
8.7
7.4
11.3
10.2
8.4
12.4
10.9
9.2
13.5
11.9
10.1
14.9
13.1
11.0
16.1
14.1
11.9
15.6
15.2
12.8
16.7
16.3
13.7
18.8
18.4
15.5
21.0
20.5
17.3
18.7
22.7
19.1
25.5
24.8
20.9
225
Seated
4.1
3.6
3.0
5.1
4.4
3.6
6.2
5.4
4.4
7.2
6.3
5.2
8.3
7.2
5.9
9.4
8.2
6.8
10.7
9.6
7.6
11.8
10.3
8.4
13.0
11.3
9.2
14.2
12.4
10.2
15.4
13.4
11.0
14.8
14.4
11.8
15.8
15.4
12.6
17.9
17.4
14.3
20.0
19.5
16.0
17.5
21.5
17.7
24.2
23.5
19.3
Torque
Force
N-m
N
80
60
40
160
120
80
270
200
140
430
330
220
660
500
330
960
720
480
1360
1020
680
1840
1380
920
2170
1630
1080
2980
2240
1490
4070
3050
2030
5420
4070
2710
5970
4470
2980
8620
6470
4310
11930
8950
5970
16060
11930
8030
20940
15700
10470
37830
28390
18960
60360
45300
30230
89160
66900
44630
123300
92500
61700
161700
121300
80900
210760
158100
105430
266760
200100
133430
328900
246700
164500
397960
298500
199030
474760
356100
237430
554760
416100
277430
508870
482100
321430
584870
554100
371210
751650
712100
474760
937430
88100
592100
1146430
1086100
724100
1374430
1302100
868100
226
CHAPTER
13
CONVERSION FACTORS
Multiply
gallon
degree C
hp
yard
kgf / cm2
kgf-m
kgf-m
kg/m3
pound
megapascal (MPa)
megapascal (MPa)
mile
newton
newton
foot
square feet
cubic feet
inches
cubic inch
square inch
By
3.785
1.8° C + 32
745,7
0.9144
14.695
9.807
7.238
6.243 x 10-2
0.454
145
10
1,609
0.225
0.102
0.305
0,09290
0.028
25.4
1,639 x 10-5
645.16
227
to get
liter
degree F
watts
meter
lbf/pol.2
newton-meter (N-m)
lbf-ft
lb/ft3
kg
lbf/pol.2
bar
km
lbf
kgf
meter
m2
m3
millimiter
cubic meter
square millimiters
228
229
230