Guidelines on Gasket Selection,

Selection Troubles, and

Countermeasures

　1. Introduction Temperature

Fluid Pressure
As Figure1 shows, we previously reported that poor
installation and poor selection account for a majority
Optimal
of sealant troubles at plants; troubles due to mis- Flange gasket selection Dimension
selection account for approximately a quarter of all
troubles. １） To ensure that sealants function properly, Tolerant leakage volume Tightening force

appropriate selection is essential. Cost Workability

This article introduces issues regarding gasket

Figure2　Selection conditions for gaskets
selection, selection methods, troubles due to selection
Winter 2018

errors, and countermeasures. example, for flanges with abnormal shapes or

extremely narrow sealant surfaces, the spiral-wound
Results of study on leakage causes (petroleum refining and chemicals)
gasket cannot be used; other gaskets such as the sheet
gasket should be selected. In some cases, gaskets with
Mis- Mis-
installation installation non-standard dimensions should be made or flanges
Mis- Mis-
selection selection should be changed.
No.34
Others Others In addition, allowable leakage volume, tightening force,
Studied by Nippon Valqua Studied by The High-Pressure Gas cost, and workability should be considered. When
2004–2013, within Japan Safety Institute of Japan 2007–2011
priority is put on functions such as small leakage
Figure 1　Statistics from study of leakage causes
volume, the product may become expensive.
Accordingly, priority conditions should be taken into
　2. Guidelines on gasket selection
account and then optimal gaskets should be selected.
２-1）Issues regarding gasket selection In addition to the above conditions, the places where
Gaskets are used under various conditions and so a gaskets are used should be considered, as the types of
wide range of conditions must be considered and then gaskets that can be used may be limited depending on
the optimal gaskets chosen. Firstly, we will study the the application and equipment. Table1 categorizes
conditions that should be considered when selecting commonly used gaskets by equipment and device. ２）
gaskets, as shown in Figure2. For example, gaskets used for devices such as the
The main conditions that must be considered without casing of pumps have complex shapes and are usually
fail are fluid, temperature, and pressure. These three thin, so only gaskets which meet such requirements
conditions must always be considered when selecting can be selected. In addition, in important stages of
gaskets. manufacturing processes and in areas where leakage
Next, the shapes and dimensions（diameter, thickness, would significantly affect the surrounding areas, a
and width）of flanges need to be confirmed. For more reliable gasket material must be selected.

21
 Technical Papers

Table1　Applicable equipment for gaskets Table2　Fluid category and typical fluids

Equipment and device Fluid category Typical fluids
Gasket type Heat Tower, tank, Water, Fresh water, industrial water, warm water, hot
Piping exchanger Valve reactor Pump
① hot water, water, water vapor, superheated vapor, boiler
Non-asbestos joint sheet ◎ ◎ ◎ ◎ ◎ water vapor water, drain, municipal effluent, sewage, etc.
Foamed carbon gasket ○ △ ○ △ ○ Crude oil,
alcohol, Crude oil, naphtha, oil gas, gasoline, light oil,
PTFE-coated gasket ◎ ○ ○ ◎ ○ animal-/ kerosene, heavy oil, tar, fuel oil, lubricating oil,
PTFE gasket containing filler ◎ ○ ◎ ◎ ○ ② plant-based common mineral oil, hydraulic oil, methanol,
oils, heat- ethanol, ethylene glycol, glycerin, animal-/plant-
Spiral-wound gasket ◎ ◎ ◎ ◎ ◎ transfer oil, based oils, heat-transfer oil, etc.
Serrated metal gasket with foamed carbon ○ ◎ △ ○ △ etc.
Metal jacketed-gasket ○ ◎ ○ ○ △ General solvents, aromatic hydrocarbon
General （including B.T.X.） ketones, amines, ethers,
Metal flat gasket △ ○ △ ○ △ solvents,
phenol, acrylonitrile, etc.
③ weak acids,
Serrated gasket △ ○ △ ○ △ weak Acetic acid, formic acid, oxalic acid, citric acid,
Ring joint gasket ◎ △ ◎ ◎ △ alkalis, etc. boric acid, phosphoric acid, etc.
Ammonia, sodium carbonate, etc.
Symbol ◎：Frequently used
Sulfuric acid, nitric acid, hydrochloric acid,
○：Used Strong permanganic acid, etc.
△：Although rarely used, usable depending on conditions. acids and
④ strong Sodium hydroxide, potassium hydroxide, calcium
alkalis hydroxide, barium hydroxide, lithium hydroxide,
２-2）Gasket-selection procedure black liquor, etc.
Air, nitrogen
Figure3 shows the gasket-selection procedure. The ⑤ gas, inert Air, nitrogen gas, helium, argon, neon, etc.
gas, etc.
details of each step are as follows: ⑥ Exhaust gas Exhaust gas
Combustible Hydrogen, methane, ethane, propane, butane,
⑦ gas
ethylene, acetylene, propylene, etc.
Fluid category
Ammonia, carbon monoxide, phosgene, sulfur
Poisonous dioxide, vinyl chloride, vinyl acetate, methylene
⑧ gas
oxide, fluorine, chlorine, bromine, iodine, hydrogen
sulfide, sulfurous acid gas, etc.
Pressure/temperature rating table Oxygen and

Winter 2018
⑨ Oxygen, ozone, liquid oxygen
others
Cryogenic LNG, LPG, liquid nitrogen, liquid hydrogen,
⑩
fluid liquefied ethylene, liquefied argon, etc.
Fluid matching table

Class

Flange’s conformance Class

No.34
e

Class
urv
or c

Class
p
-va
ted

Class
ura

Gasket’s shape and dimension

Sat

Class
Recommended Other usable
gaskets gaskets
Joint sheet
Figure3　Selection conditions for gaskets
Pressure

Class
High-performance Joint sheet
sheet （Vapor pressure）
High-performance sheet
STEP 1 Fluid category
Spiral-wound gasket Spiral-wound gasket
（Foamed carbon） （Inorganic paper）
Confirm the fluid category based on the types of fluid Spiral-wound gasket
（Mica）
in use. There are 10 fluid categories as listed below. Ring joint
Table2 summarizes the typical fluids of each category.
temperature

STEP 2 Pressure/temperature rating table Figure 4　‌Temperature/pressure selection graph for water,
hot water, water vapor
Select an appropriate pressure/temperature selection
graph for the fluid category. Then, select usable conditions intersect at the point ② , so a high-
gaskets based on the pressure and temperature which performance sheet gasket is selected.
will be applied to the gaskets. For example, when the
fluid is water vapor with a pressure of 1 MPa and a STEP 3 Fluid matching table
temperature of 180C, the fluid category is ① water, Use the fluid matching table to confirm whether the
hot water, and water vapor. Figure4 shows a selection gasket selected in Step 2 can be used for the intended
graph. In the graph, the pressure and temperature fluid. If the gasket is not suitable, go back to Step 2

22
 Guidelines on Gasket Selection, Selection Troubles, and Countermeasures

and select“other usable gaskets”or higher-category Table5　Matching table for flange seats and spiral-wound gaskets
Nominal Nominal
gaskets. Table3 shows a fluid matching table for ① 26 ～ 1/2 ～ diameter pressure Class Class Class
60B 24B Gasket seat 150 300 to 600 900 to 1500
water, hot water, and water vapor as an example. With inner and
outer rings Raised With inner and outer rings
Under the conditions shown in Step 2, the fluid is face
With outer（flat face） With outer ring（1）
（2）

water vapor. Therefore, the selected high-performance ring（1）（2）

With inner ring Male-and- With inner ring
sheet gaskets are considered to be applicable. female
shape
Table 3　Matching table for water, hot water, water vapor
Basic shape
Groove
Basic shape（3）
8590 Series

High-
6502

Fluid Segment
performance shape
・ 6503
7GP66

sheet 1500
7010
6500

VF-30

M590L Series

（ reference
8590L Series

N7030 Series

Type of Fluid
・
・

M590 Series
・ 8590TN
・ 6500AC

・ 6503AC

6590 Series

7590 Series
・ VF-35E

Note（1）‌When filler is foamed carbon or PTFE, gaskets with inner

7010-EX
7GP66S
MF300
UF300

GF300

SF300

and outer rings are recommended.

7020

7026

Fluid
）

（2）‌When fluid is monomer, gaskets with inner and outer rings

warm water・hot water・ ○
boiler feedwater ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
are recommended.
（3）‌In the case of flanges with large nominal diameter, gaskets
water

clear water・industrial ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
water
with inner rings are recommended for easy handling.
・ steam

steam・superheat steam ○ ○ ○ ○ △ △ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
water’hot water’steam

drain・municipal effluent・
STEP 5 Gasket’s shape/dimensions
dirty water ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

calcium chloride ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
aqueous solution of a neutral salt

Finally, determine the gasket’s shape and dimensions

sodium chloride ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

seawater ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ to confirm whether the gasket can be manufactured. If

sodium nitrate ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
the gasket cannot be manufactured, go back to Step 2
sodium fluoride ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
and re-select.
Winter 2018

Sodium sulfate ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

In addition, confirm whether the selected gasket can

accommodate the gasket’s tightening force. Regarding
STEP 4 Flange’s conformance ease of tightening/removal, cost effectiveness, and
Confirm whether the selected gasket can be used market availability（delivery）
, determine which factors
for the shape of the flange’s gasket seat. Table4 is a should be prioritized and select the optimal gasket.
matching table to check whether a selected soft When selecting gaskets based on fluid, temperature,
No.34
gasket is suitable for a flange’s gasket seat. Table5 is a and pressure conditions, please use our Gasket catalog
matching table to check whether a selected spiral- （No. YC08）and Seal Quick SearcherTM, which is a
wound gasket is suitable for a flange’s gasket seat and useful website for selection. ３）
nominal pressure/diameter.
２-3）‌Fluids which require care when selecting
Table4　Matching table for flange sheets and soft gaskets
Gasket Flange-seat type The following fluids require particular care when
Male-and-
Flat face Raised face female shape
Groove
shape
selecting:
Type Shape ①　Oxygen and combustion-supporting gas: Gaskets
containing combustible material should be
Joint sheet/high- FF ● ● － － avoided.
performance sheet
Fluororesin sheet
FR ● ● ● ● Spiral-wound gaskets containing PTFE filler,
（containing filler） by
16K
by
20K

Fluororesin sheet FF － － － － PTFE-blended gasket, copper jacketed-gasket,

（Simple substance） FR － － ● ● and solid-metal flat gasket are recommended.
FF ▲ － － －
Fluororesin jacket ②　P o l y m e r i z a b l e m o n o m e r : P o l y m e r i z a b l e
FR ● ● － －
Foamed carbon FF ▲ － － － monomers including styrene monomer and vinyl
sheet FR ● ● ▲ ▲ chloride monomer can cause malfunctions in the
joint sheet and PTFE-blended gasket. The spiral-
wound gasket with inner and outer rings and the

23
 Technical Papers

metal gasket are recommended.

　3. Troubles
‌ due to mis-selection and
③　 Fluid containing slurry: Soft gaskets can be
countermeasures against the troubles
damaged and leak due to erosion.
The spiral-wound gasket with inner and outer Previously, examples of troubles due to fluid
rings and the metal gasket are recommended. mismatch were introduced.４） Following are other
④　H eat-transfer oil: The joint sheet can suffer examples of troubles due to mis-selection.
deterioration in its rubber binder, resulting in
leakage. Moreover, oil has high permeability. ３-1）Thermal degradation in the joint sheet gasket
Therefore, the spiral-wound gasket containing One of the constituent materials of the joint sheet
non-asbestos filler can suffer leakage when used gasket is a rubber binder. When the temperature
for a long time. The foamed-carbon sheet gasket exceeds 100ºC, the binder hardens, making the whole
and spiral-wound gasket containing foamed gasket harder. In this state, external force such as
carbon filler are recommended. additional tightening and piping stress can cause the
⑤　Radioactive fluid: PTFE is vulnerable to radiation, gasket to crack as shown in Figure5. When additional
and so PTFE gaskets are not recommended. tightening is applied during maintenance, the joint
6
Foamed carbon has radiation resistance of 1.0×10 Gy; sheet gasket should generally be used at a
make a selection after checking the radiation dose. temperature of less than 100ºC. If the temperature is
over 100ºC, high-performance sheet gaskets including
２-4）Thickness selection No. GF300, which does not contain rubber binder, are

Winter 2018
Table6 shows the relationship of gasket thickness to recommended.
gasket characteristics regarding the seat gasket. The
thicker a gasket is, the greater its compression
amount. A thicker gasket can better absorb a flange’s
strain and swelling. On the other hand, the thinner a
gasket is, the smaller the penetration-leakage volume
No.34
is, resulting in superior sealing properties. At the same
time, a thinner gasket has weaker creep relaxation,
resulting in superior long-term stability. In terms of
compression-failure characteristics, thinner gaskets are
more tolerant to external force. From the above,
thinner gaskets are recommended in principle. Figure5　Cracked joint sheet gasket due to hardening

However, when flanges with large nominal diameters On the other hand, when gaskets are used in
have large swelling and strain in the flange and when equipment, to reduce the leakage volume and
flanges have some roughness on the surface due to deterioration, thinner gaskets are used to cause stress
long-term use, the strain needs to be absorbed. relaxation less frequently, or the gaskets are initially
Therefore, thicker gaskets are recommended. tightened at a contact pressure of over 30 MPa.4）
Table6　Gasket thickness and characteristics（sheet gasket） When the joint sheet is used at temperatures
Gasket thickness exceeding 100ºC, the following countermeasures are
Characteristics
Thin Thick recommended to avoid additional tightening:
Compression amount Little Large ①　Set the gasket thickness at 1.5 mm or less.
Seal property Strong Weak ②　Apply gasket paste（including seal paste）to the
Creep relaxation Little Large gasket.
Compression failure contact pressure Strong Weak
③　Set the initial tightening contact pressure at over

24
 Guidelines on Gasket Selection, Selection Troubles, and Countermeasures

30 MPa.
④　Use a joint sheet gasket in areas where pipe stress
is less likely to occur and where gaskets can be
replaced easily.
⑤　T o increase the gasket-tightening contact
pressure, use a ring gasket with a gasket outer
diameter equal to the bolt’s bore diameter.

３-2）‌Deformation of fluororesin-blended sheet gaskets

Fluororesin-blended gaskets tend to occur creep
relaxation even at room temperature. Especially, when
gaskets made solely from fluororesin are used, Figure7　Deformation of a spiral-wound gasket
deformation due to creep relaxation must be
considered carefully; in principle, grooved flanges inner and outer rings is recommended.
should be used. When the fluid is a monomer, the gasket with inner
In addition, the creep relaxation characteristics of and outer rings is also recommended to inhibit
fluororesin become more prominent at high penetration and polymerization.
temperature, leading to greater deformation due to
softening as shown in Figure6. Therefore, when the ３-4）Troubles due to errors in selecting dimensions
Winter 2018

temperature exceeds 100ºC, a filler should be added, or Originally, the gasket’s dimension must be set to
gaskets containing less fluororesin should be selected match the flange’
s dimension. If they do not match, the
in order to reduce creep relaxation. gasket may leak. For example, when the gasket’s
diameter is smaller than that of a raised-face flange,
the gasket will cause inaccurate centering, causing
misalignment and partial narrowing on the gasket’s
No.34
contact surface as shown in Figure8. The narrow
contact surface cannot bear the inner pressure and is
pushed toward the outer diameter, sometimes
resulting in deformation or rupture. The misalignment
also pushes the whole gasket within the piping’s inner
diameter. The protrusion may damage the gasket and
cause leakage.

Figure6　Deformation of a fluororesin sheet gasket

３-3）Deformation of spiral-wound gaskets

Regarding spiral-wound gaskets containing foamed- Gasket

carbon filler or PTFE filler, when a spiral-wound Flange seat

gasket with outer ring is used, the filler slides. As

shown in Figure7, the sliding may cause buckling
deformation on the inner-diameter side, weakening the
sealing properties. Therefore, when the filler is Figure8　Deformation due to gasket misalignment
foamed carbon or PTFE, the spiral-wound gasket with

25
 Technical Papers

３-5）Troubles due to corrosion metals, a cell is formed, sometimes resulting in

One example of gasket-induced corrosion is“deposit corrosion of the flange. To prevent this corrosion, the
corrosion,”which occurs by fluid penetrating the gap flange joint assembly must be insulated. High
between the gasket and flange or the gasket itself, insulation gaskets include fluororesin-blended gaskets
then chlorine ions in the fluid cause corrosion. such as fluororesin jacketed-gaskets. Not limited to
Especially when stainless-steel flanges are used in gaskets, insulation, including the use of insulating bolts
seawater, which contains many chlorine ions, corrosion to insulate screw parts, is recommended.
is more likely to occur. Tightening contact pressure is
weak in the inner-diameter area of the contact surface 　4. Conclusion
between a flange and gasket, resulting in minute
spaces more frequently. When fluid containing chlorine This report explained gasket selection, selection
ions penetrates the gap between the stainless-steel methods, troubles due to selection errors and
flange and gasket or penetrates within the gasket, the countermeasures. For further details on gasket
stainless steel forms a passivation film. This reaction selection, please refer to our Gasket catalog（No.
creates an oxygen concentration cell, reducing pH and YC08）and Seal Quick SearcherTM, which is a useful
increasing the chlorine-ion concentration and leading to website for selection. For other selection conditions
rapid deterioration of the flange metal or deposit than described in the catalog or website, please
5）
corrosion. To prevent this deposit corrosion, it is contact us.
effective to use a gasket with a low chlorine content We believe that by studying the issues and procedures

Winter 2018
and to apply an anticorrosion paste（seal paste）to regarding proper product selection, leakage troubles
eliminate the gaps. Regarding tightening, the following due to gaskets can be prevented. We hope this report
measures may be used: apply a greater gasket contact was helpful.
pressure, modify the flange’s strain, and smooth the
flange seat. 　5. References
Galvanic corrosion may develop at the junction
No.34
between different metal flanges, and occurs as follows: １）‌R. Ikeda, Valqua Technology News No. 31, pp. 2–7;
1）Metals with different ionization tendency come into 2016.
contact with each other, 2）When the metals are ２）‌Valqua Handbook. No. 92（2011）.
immersed in an electrolyte solution, a potential ３）‌T. Enisi, Valqua Technology News. No. 32, pp. 22–25
difference occurs in the space between the metals, （2017）.
forming a galvanic cell, and 3）The galvanic cell ４）‌T. Enisi, Valqua Technology News. No. 33, pp. 2–3;
corrodes the metal with lower ionization tendency. 2017.
When gaskets with high conductivity including metals ５）‌T. Nishida: New Gaskets and Gasketing Technology.
are used in a flange’s junction between different p. 87（2015）.

Asuka Matsushita
Sales Group
Technical Solution Division

26