Troubles While Mounting Gaskets
and Countermeasures
1. Introduction
The term seal means to prevent a fluid from leaking

circumference does not need to be welded completely;
partial side spot welding or simple welding issufficient.

from inside to outside or from outside to inside in piping,Common typedevices, and equipment at various plants and themembers for such purposes. To achieve sealing as

Circumference-sutured type

intended, not only the seals themselves but also theproper selection and application of seals are important.

Circumference-fusion bonded type(partial or simplified fusion)

Among sealing-related information, we previously

Summer 2017

introduced gasket-tightening troubles andcountermeasures1）. This report introduces additional
troubles that may occur while mounting gaskets andcountermeasures.

※）Note: The circumference-sutured type can be used only in gaskets withdiameters of φ400 or narrower. When circumference-sutured types are
not applicable, circumference-fusion bonded types can be used.

Figure1

Jackets of fluorocarbon resin envelope gaskets2-2）Wetting of a felt sheet of a fluorocarbon
resin envelope gasket

2. Examples of Mounting Troubles
and Countermeasures

Some No.N7030-series fluorocarbon resin envelope2-1）Jacket's fold-over in fluorocarbon resin

sheet is vulnerable to compression fracture when it isNo.33

envelope gaskets
The fluorocarbon resin envelope gaskets, No.N7030

gaskets use felt sheets as their cores; however, a felt
wet. Therefore, they should not be mounted andtightened in rainy weather.

series, have the jacket sideways V- or U--shaped crosssection, all of which have openings on the side ofoutside diameter. Due to such jacket’s structure, when2-3）Scratching on the surface of expandedgraphite gaskets

a gasket is mounted, especially when it is mounted

Expanded graphite material has ideal properties as a

into a narrow space inside a flange, the gasket's

seal material including excellent chemical resistance

fluorocarbon resin jacket sometimes folds over and isand minimal creep relaxation; on the other hand, it has

tightened while the jacket is left bent toward thehandling disadvantages including vulnerability andinside. This bent part causes a level difference whichfragility. If expanded graphite gaskets are roughly

becomes a channel for leakage, resulting in poor

handled during transportation or mounting, it could besealing. Therefore, care should be taken not to cause aeasily to develop leakage channels on the surface andfluorocarbon resin jacket to fold over when mounting.

the risk of poor sealing.

Fold-over can be prevented by using the following

Therefore, the following products should be stored

countermeasure products whose outer sides areand transported in the packaged condition to prevent

adhered and closed. In such products, the wholesurface scratching: the expanded graphite sheet

11Technical Papers

gasket; No.VF-35E, the expanded graphite spiralwound gasket; No.6590 series, the serrated metal2-5）Misaligned mounting of large-diameterspiral wound gaskets

gasket with expanded graphite sheet: No.6540H, theIn a male-female flange and groove flange which havemetallic flat gasket with expanded graphite attached:a large roughness clearance, especially in a vertically

No.6560, and the metal jacketed gasket with expanded

placed spiral wound gasket, the main body of thegraphite attached: No.N6520. Also, care should begasket is dislocated from the flange face, and thetaken when mounting them, such as avoiding

flange face edge sometimes contacts the inside area ofscratching the gaskets with sharp objects including

seal body. In this case, a spiral wound gasket might

nails and tools and not placing them directly on the

protrude beyond the gap, resulting in breakage orground.

leaking.
Therefore, for a spiral wound gasket used in a heat2-4）Breakage of large-diameter spiral woundexchanger, the number of the inner metal strip

gaskets in pre-utilization conditions

without filler and the number of spot welding applied

including transportation

to each winding are increased; in addition, the gasket’s outer diameter is manufactured to ensure over-easily, but large-diameter spiral wound gaskets withtolerance . These approaches reduce the risk ofor without inner / outer rings have a risk of breakage

protrusion, breakage, and leakage even when the main（so-called loosening）when excessive force is applied

body is dislocated from the flange face.

during storage, unpacking, transportation, andWhen such problems occur despite these approaches,mounting. Especially, spiral wound gaskets with aadditional metal strip without filler for a 3.2-mm main

diameter of over 2000 mm have higher risks. If thebody can be applied to the outside and inside of thegaskets break, they cannot be used anymore.

regular 4.5-mm main body. This process can prevent

Therefore, take care not to apply excessive force

the main body from becoming dislocated from theincluding twisting and strain to these products.

flange face. Also, for the same purpose, a metallic

・Avoid placing a gasket in the standing position; theround bar can be placed inside.

No.33

horizontal position is desirable.
・Do not forcibly dismount fixtures when unpacking（a written unpacking procedure is enclosed with alarge-diameter spiral wound gasket; read and follow
the dismounting steps）.
・The number of staff required for transportation andmounting varies depending on the product's size.
The following table shows the ideal number of staff
for the operation.

Ideal
configuration

Figure2

An example in which themain body is dislocatedfrom the flange buckling

An example in which a
3.2-mm hoop is added tokeep the main body within
the flange buckling ositional relation of spiral wound gaskets toP
flange face

Other than the above-mentioned approaches, theTable1

Approximate number of staff required to handle
gaskets of a given size

Summer 2017

Small-diameter spiral wound gaskets do not breakfollowing mounting method can be used: for tentative
holding, a retainer plate and bolts specialized for theGasket's inner diameter

Number of handling staff

1000 ～ 1500 mm

2 or 3

retainer plate are used to hold the gasket in an

1500 ～ 2000 mm

3 or 42000 ～ 3000 mm

4 to 6

appropriate position; guide bolts are used to3000 ～ 4000 mm

6 to 8appropriately adjust the flange; the gasket is tentatively
held with bolts which are used in actual equipment;
then, the retainer plate is removed and final tightening
is applied to the gasket.
12Troubles While Mounting Gaskets and Countermeasures2-6）Mounting a metal jacketed gasket in thewrong direction

then the gasket can be used.
When contact is not confirmed on the whole

When a metal jacketed gasket is used in a male-circumference, grinding is needed. Also, grinding isfemale flange or groove flange and the metal jacket isused to remove scratches and corrosion of a flange's

mounted in such a direction that the folded part of thegroove. In the grinding process, polishing powders aremetal jacket contacts with the convex part of theapplied to the gasket and then the gasket is rotated inflange, the flange's convex edge sometimes breaks thethe flange's groove. Red lead primer or otherfolded part of the metal jacket during tightening.

pigments are used to confirm whether whole-Therefore, a metal jacketed gasket needs to be

circumference contact is achieved. In the case of anmounted in such a manner that the folded part becomes

octagonal type, grinding can be performed by using

the groove bottom. In addition, since the gasket has anan octagonal gasket itself which is to be mounted.

inside and an outside, in the case of non-symmetrical

However, in the case of an oval type, grinding using

branching gaskets, mounting instructions clarifying

an oval gasket itself reduces the excellent sealing

the direction of the metal folded part must be

properties attained through line contact, so, anincluded on the drawing.

octagonal gasket or tool specialized for grinding isused for the process.
In addition, in the case of gas seal and in case of using
hard materials such as stainless steel, the gasket paste

Summer 2017

should be thinly applied.
When sealing functions are inadequate despite
Figure3

Mounting direction of a metal jacketed gasket

countermeasures can be taken: replacing the gasket
with a ring joint gasket loaded with a cover made of a2-7）Incomplete contact of a metal ring joint

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applying gasket paste, the following othergasket to a flange
When both a flange and a gasket are new, no contact

soft material including expanded graphite or copper,
or arranging a gasket in a special dimension fitted fora flange.

problems would occur; however, when a ring joint
gasket is used in a flange that has been used for a2-8）Common checks for all gaskets

long time, incomplete contact between the flange andCommon checks for all gaskets while mounting are as

gasket sometimes results in inadequate sealing.

follows:

Therefore, firstly it is necessary to confirm whether

・Whether a flange has rust, scratches, or dents

the whole circumference of the gasket contacts withwhich adversely affect the flange's sealing

the flange（hereafter, contact）. To confirm this,pigments including red lead primer are applied to thegasket, the gasket is tightened to approximately 20%of the target torque, and then it is opened to checkproperties
・Whether part of a gasket which was previously
used adheres to the flange
・Whether the gasket's surface has scratches or

how the pigments remain on the surfaces.

adhesion of foreign substances

Confirmation can be conducted either on the outside（Especially, if a bolt hole has foreign substances

or inside contact（when the pressure is high, theinside while an upper bolt is being inserted in aoutside is desirable）, to check whether contact ishorizontal pipe, the substance can fall off andpresent on the whole circumference（line contact isadhere to a gasket.）acceptable）. After whole-circumference contact is・Whether the gasket's dimensions are correct

confirmed, the gasket is appropriately tightened, and（Even when a gasket has the same outside

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Technical Papers

diameter as the specifications, sometimes, the innerfor various types of gasket. Since customers conduct

diameter is different from the specifications. In suchsealing themselves, we hope this report will help themcases, smaller inner diameters can cause leakage

to avoid leakage troubles and achieve sealing as

into a channel.）intended.

・Whether the gasket type is correct

4. Reference

3. Conclusion

1）Takahiro Fujihara, VALQUA Technology News No.

This report introduced troubles occurring while

31, pp. 8–11; 2016

mounting gaskets and countermeasures against them,

Satoshi Akiyama
Sales Group

Technical Solution Division

Summer 2017
No.33

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