Guidelines on Gasket Selection,
Selection Troubles, andCountermeasures
1. Introduction

Temperature

As Figure1 shows, we previously reported that poor

Fluid

Pressure

installation and poor selection account for a majority
of sealant troubles at plants; troubles due to mis-

Optimalgasket selection

FlangeDimension

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

This article introduces issues regarding gasket

Winter 2018selection, selection methods, troubles due to selection

Results of study on leakage causes (petroleum refining and chemicals)

No.34

Studied by Nippon Valqua
2004–2013, within Japan

Figure 1

Selection conditions for gaskets

example, for flanges with abnormal shapes or

errors, and countermeasures.

Misinstallation
Misselection
OthersFigure2Workability

Misinstallation
Misselection
OthersStudied by The High-Pressure Gas
Safety Institute of Japan 2007–2011

Statistics from study of leakage causes

2. Guidelines on gasket selection

extremely narrow sealant surfaces, the spiral-woundgasket cannot be used; other gaskets such as the sheet
gasket should be selected. In some cases, gaskets with
non-standard dimensions should be made or flanges
should be changed.
In addition, allowable leakage volume, tightening force,cost, and workability should be considered. Whenpriority is put on functions such as small leakage
volume, the product may become expensive.
Accordingly, priority conditions should be taken into
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 agaskets are used should be considered, as the types ofwide range of conditions must be considered and thengaskets that can be used may be limited depending on

the optimal gaskets chosen. Firstly, we will study thethe 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 threethin, so only gaskets which meet such requirements

conditions must always be considered when selecting

can be selected. In addition, in important stages ofgaskets.

manufacturing processes and in areas where leakage

Next, the shapes and dimensions（diameter, thickness,would significantly affect the surrounding areas, aand width）of flanges need to be confirmed. For

more reliable gasket material must be selected.

21

Technical Papers

Table1

Gasket type

PipingNon-asbestos joint sheet◎
Foamed carbon gasket○
PTFE-coated gasket◎
PTFE gasket containing filler◎
Spiral-wound gasket◎
Serrated metal gasket with foamed carbon○
Metal jacketed-gasket○
Metal flat gasket△
Serrated gasket△
Ring joint gasket◎
SymbolTable2

Applicable equipment for gaskets
Heat
exchanger

tank,
Valve Tower,
Pump
reactor

◎
△
○
○
◎
◎
◎
○
○
△

◎
○
○
◎
◎
△
○
△
△
◎

◎
△
◎
◎
◎
○
○
○
○
◎

Fluid category and typical fluids

Fluid category

Equipment and device
◎
○
○
○
◎
△
△
△
△
△

◎：Frequently used○：Used△：Although rarely used, usable depending on conditions.

Typical fluids

Fresh water, industrial water, warm water, hot
Water,① hot water, water, water vapor, superheated vapor, boiler
water vapor water, drain, municipal effluent, sewage, etc.

②

Crude oil,alcohol,animal-/plant-based
oils, heattransfer oil,etc.

③

General（including B.T.X.） ketones, amines, ethers,
solvents,
phenol, acrylonitrile, etc.
weak acids,
Acetic acid, formic acid, oxalic acid, citric acid,weak
alkalis, etc. boric acid, phosphoric acid, etc.

Crude oil, naphtha, oil gas, gasoline, light oil,kerosene, heavy oil, tar, fuel oil, lubricating oil,common mineral oil, hydraulic oil, methanol,
ethanol, ethylene glycol, glycerin, animal-/plantbased oils, heat-transfer oil, etc.
General solvents, aromatic hydrocarbon

Strongacids and④ strong

alkalis２-2）Gasket-selection procedure

Air, nitrogen

Ammonia, sodium carbonate, etc.
Sulfuric acid, nitric acid, hydrochloric acid,permanganic acid, etc.
Sodium hydroxide, potassium hydroxide, calcium
hydroxide, barium hydroxide, lithium hydroxide,
black liquor, etc.

Figure3 shows the gasket-selection procedure. The⑤ gas, inert

details of each step are as follows:⑥ Exhaust gas Exhaust gas

gas, etc.

Air, nitrogen gas, helium, argon, neon, etc.

Combustible Hydrogen, methane, ethane, propane, butane,

Fluid category⑦ gas

Poisonous⑧ gas⑨

Oxygen andOxygen, ozone, liquid oxygen
others⑩

Cryogenic LNG, LPG, liquid nitrogen, liquid hydrogen,fluidliquefied ethylene, liquefied argon, etc.

Fluid matching table

Winter 2018

Pressure/temperature rating table

ethylene, acetylene, propylene, etc.
Ammonia, carbon monoxide, phosgene, sulfur
dioxide, vinyl chloride, vinyl acetate, methyleneoxide, fluorine, chlorine, bromine, iodine, hydrogensulfide, sulfurous acid gas, etc.

Class

Flange’s conformanceClass

Selection conditions for gaskets

STEP 1 Fluid category

e
or c
ted
Sat

ura

Class
Class

Pressure

Figure3

-va
p

Class

Gasket’s shape and dimension

High-performance Joint sheet（Vapor pressure）
sheet
High-performance sheet
Spiral-wound gasket Spiral-wound gasket（Foamed carbon） （Inorganic paper）
Spiral-wound gasket（Mica）

in use. There are 10 fluid categories as listed below.

Ring joint

Table2 summarizes the typical fluids of each category.

Select an appropriate pressure/temperature selection

Recommended Other usablegaskets
gaskets
Joint sheet

Class

Confirm the fluid category based on the types of fluid

STEP 2 Pressure/temperature rating table

No.34

urv

Class

temperature

Figure 4‌Temperature/pressure selection graph for water,
hot water, water vapor

graph for the fluid category. Then, select usableconditions 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 thefluid is water vapor with a pressure of 1 MPa and a

STEP 3 Fluid matching tabletemperature 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 Countermeasuresand select“other usable gaskets”or higher-category

Table5 Matching table for flange seats and spiral-wound gaskets

gaskets. Table3 shows a fluid matching table for

26 ～
60B

①

water, hot water, and water vapor as an example.
Under the conditions shown in Step 2, the fluid iswater vapor. Therefore, the selected high-performance
sheet gaskets are considered to be applicable.
Table 3NominaldiameterNominalpressure

Gasket seat

With inner andouter rings

Raisedface
With outer（flat face）
ring（1）（2）With inner ring

Male-andfemale
shape

Class
150

Class
Class
300 to 600 900 to 1500

With inner and outer rings（2）
With outer ring（1）With inner ring

Matching table for water, hot water, water vapor

SF300

・ 6500AC
6500

・ 6503・ 6503AC
6502

7010-EX
7GP66S

7020

7026

・ VF-35E
VF-30・ 8590TN
8590 Series
8590L Series

6590 Series

7590 Series

M590 Series
M590L Series

N7030 Series（ reference
）
1500

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

clear water・industrial ○
water

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

steam・superheat steam ○

○

○

○

△

△

○

○

○

○

○

○

○

○

○

○

drain・municipal effluent・○
dirty water

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

STEP 5 Gasket’s shape/dimensions

calcium chloride

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

sodium chloride

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

Finally, determine the gasket’s shape and dimensions

seawater

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

sodium nitrate

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

sodium fluoride

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

Sodium sulfate

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○

Highperformance
sheet

Type of Fluid

Fluid

・
7010
・
7GP66

GF300

Basic shape

UF300

Groove
shape

MF300

Basic shape（3）warm water・hot water・ ○boiler feedwater

Fluid Segment

aqueous solution of a neutral salt

water’hot water’steam

・ steamwater

Winter 2018
No.34

1/2 ～
24B

Note（1）‌When filler is foamed carbon or PTFE, gaskets with innerand outer rings are recommended.
（2）‌When fluid is monomer, gaskets with inner and outer rings
are recommended.
（3）‌In the case of flanges with large nominal diameter, gaskets
with inner rings are recommended for easy handling.

to confirm whether the gasket can be manufactured. If
the gasket cannot be manufactured, go back to Step 2
and re-select.
In addition, confirm whether the selected gasket canaccommodate the gasket’s tightening force. Regarding
ease of tightening/removal, cost effectiveness, andSTEP 4 Flange’s conformance

Confirm whether the selected gasket can be usedmarket availability（delivery）, determine which factors

for the shape of the flange’s gasket seat. Table4 is ashould be prioritized and select the optimal gasket.

matching table to check whether a selected soft

When selecting gaskets based on fluid, temperature,gasket is suitable for a flange’s gasket seat. Table5 is aand pressure conditions, please use our Gasket catalog

matching table to check whether a selected spiral-（No. YC08）and Seal Quick SearcherTM, which is awound gasket is suitable for a flange’s gasket seat anduseful website for selection. ３）

nominal pressure/diameter.
Table4

Matching table for flange sheets and soft gaskets
GasketFlange-seat typeMale-andFlat face Raised face female
shape

Type

Groove
shape

Shape

２-3）‌Fluids which require care when selecting
The following fluids require particular care whenselecting:①

Oxygen and combustion-supporting gas: Gaskets
containing combustible material should be

Joint sheet/highperformance sheet
Fluororesin sheet（containing filler）

avoided.

FF

●

●

－

FR

●

●

● by

FF
Fluororesin sheet（Simple substance） FR

－

－

－

－

PTFE-blended gasket, copper jacketed-gasket,

－

－

●

●

FF

▲

－

－

－

and solid-metal flat gasket are recommended.

FR

●

●

－

－

Fluororesin jacket
Foamed carbon
sheet

－
16K

● by

20K

	Spiral-wound gaskets containing PTFE filler,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

FF

▲

－

－

－

monomers including styrene monomer and vinyl

FR

●

●

▲

▲

chloride monomer can cause malfunctions in the
joint sheet and PTFE-blended gasket. The spiralwound gasket with inner and outer rings and the23Technical Papers

metal gasket are recommended.
③

3. Troubles‌
due to mis-selection andcountermeasures against the troubles

 Fluid containing slurry: Soft gaskets can bedamaged 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H eat-transfer oil: The joint sheet can suffer

examples of troubles due to mis-selection.

④

deterioration in its rubber binder, resulting in⑤leakage. 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 usedgasket is a rubber binder. When the temperature

for a long time. The foamed-carbon sheet gasket

exceeds 100ºC, the binder hardens, making the wholeand spiral-wound gasket containing foamed

gasket harder. In this state, external force such ascarbon filler are recommended.

additional tightening and piping stress can cause theRadioactive fluid: PTFE is vulnerable to radiation,

gasket to crack as shown in Figure5. When additionaland 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 amake a selection after checking the radiation dose.

temperature of less than 100ºC. If the temperature isover 100ºC, high-performance sheet gaskets including
No. GF300, which does not contain rubber binder, areTable6 shows the relationship of gasket thickness torecommended.

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

Winter 2018２-4）Thickness selection

strain and swelling. On the other hand, the thinner agasket is, the smaller the penetration-leakage volume

No.34

is, resulting in superior sealing properties. At the sametime, a thinner gasket has weaker creep relaxation,
resulting in superior long-term stability. In terms ofcompression-failure characteristics, thinner gaskets are
more tolerant to external force. From the above,
Figure5thinner gaskets are recommended in principle.

Cracked joint sheet gasket due to hardening

However, when flanges with large nominal diameters

On the other hand, when gaskets are used inhave large swelling and strain in the flange and whenequipment, to reduce the leakage volume andflanges have some roughness on the surface due todeterioration, thinner gaskets are used to cause stresslong-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

Characteristics

exceeding 100ºC, the following countermeasures are

Gasket thickness
Thin

Thick

recommended to avoid additional tightening:

Compression amountLittleLarge① Set the gasket thickness at 1.5 mm or less.

Seal property

StrongWeak②

Creep relaxation

LittleLarge

Compression failure contact pressure

StrongWeak

Apply gasket paste（including seal paste）to thegasket.

③

Set the initial tightening contact pressure at over24

Guidelines on Gasket Selection, Selection Troubles, and Countermeasures

30 MPa.
④

Use a joint sheet gasket in areas where pipe stressis less likely to occur and where gaskets can be
replaced easily.

⑤ T o increase the gasket-tightening contactpressure, 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, whengaskets 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 innerIn addition, the creep relaxation characteristics ofand outer rings is also recommended to inhibit

fluororesin become more prominent at highpenetration and polymerization.

temperature, leading to greater deformation due toWinter 2018softening as shown in Figure6. Therefore, when the３-4）Troubles due to errors in selecting dimensions

temperature exceeds 100ºC, a filler should be added, orOriginally, the gasket’s dimension must be set togaskets containing less fluororesin should be selected

match the flange’s dimension. If they do not match, thein 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 narrowcontact surface cannot bear the inner pressure and ispushed toward the outer diameter, sometimes
resulting in deformation or rupture. The misalignment
also pushes the whole gasket within the piping’s innerdiameter. The protrusion may damage the gasket andcause leakage.
Figure6

Deformation of a fluororesin sheet gasket３-3）Deformation of spiral-wound gaskets
Regarding spiral-wound gaskets containing foamed-

Gasketcarbon filler or PTFE filler, when a spiral-wound

Flange seatgasket with outer ring is used, the filler slides. As
shown in Figure7, the sliding may cause buckling
deformation on the inner-diameter side, weakening thesealing properties. Therefore, when the filler isfoamed carbon or PTFE, the spiral-wound gasket with
25

Figure8

Deformation due to gasket misalignment

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, thecorrosion,”which occurs by fluid penetrating the gap

flange joint assembly must be insulated. Highbetween 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 ingaskets, 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
between a flange and gasket, resulting in minute

4. Conclusion

spaces more frequently. When fluid containing chlorine

This report explained gasket selection, selection

ions penetrates the gap between the stainless-steelmethods, troubles due to selection errors andflange and gasket or penetrates within the gasket, thecountermeasures. 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 usefulincreasing 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, pleasecorrosion.

5）

To prevent this deposit corrosion, it iscontact us.
We believe that by studying the issues and procedures

and to apply an anticorrosion paste（seal paste）toregarding proper product selection, leakage troubles

eliminate the gaps. Regarding tightening, the following

due to gaskets can be prevented. We hope this reportmeasures may be used: apply a greater gasket contact

was helpful.

pressure, modify the flange’s strain, and smooth theflange seat.
Galvanic corrosion may develop at the junction
between different metal flanges, and occurs as follows:1）Metals with different ionization tendency come into

5. References
１）‌R. Ikeda, Valqua Technology News No. 31, pp. 2–7;
2016.

contact with each other, 2）When the metals are２）‌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,
forming a galvanic cell, and 3）The galvanic cellcorrodes the metal with lower ionization tendency.
When gaskets with high conductivity including metals
are used in a flange’s junction between different

Winter 2018

effective to use a gasket with a low chlorine content（2017）.
４）‌T. Enisi, Valqua Technology News. No. 33, pp. 2–3;
2017.
５）‌T. Nishida: New Gaskets and Gasketing Technology.
p. 87（2015）.

Asuka Matsushita
Sales Group
Technical Solution Division26

No.34