Sheet Gaskets for High-Temperature Use
VALQUA HEAT RESIST SHEET™ No. HRS
1. Introduction

Summer 2018

Under high-temperature conditions in petroleum refining2-1）Compositionand petrochemistry industries, spiral wound gaskets,

No. HRS is a white sheet consisting of inorganic

metal jacketed gaskets, ring joint gaskets, and rubber-materials. Like foamed carbon sheet No. VF-35E, No.

coated woven fabric gaskets are used. Appropriate

HRS is made by fixing a sheet material on both surfaces

gaskets are selected depending on the pressure classes.

of a stainless-steel thin plate（thickness：0.05 mm）.

Among such gaskets, rubber-coated woven fabricFigure1 is a photograph of the exterior and Figure2gaskets are used under low-pressure conditions and areshows the composition.

not dense, so they cannot provide adequate sealing2-2）Characteristics

properties. Furthermore, due to material deterioration,① Compared with the conventional rubber-coatedthey carry risks regarding medium- to long-term sealing

woven fabric gasket, No. HRS offers significantlyproperties. In addition, refractory ceramic fiber（RCF）,

improved sealing properties, effectively reducing

which is a constituent material of the rubber-coatedthe discharge of environmental contaminants

woven fabric gasket, was categorized as a Group-2

No.35

2. Composition and characteristics

including NOx and SOx in combustion gas.

substance and specified chemical substance to be② N o. HRS minimizes the content of organic

controlled under the Ordinance on the Prevention ofconstituents including rubber binder. In addition,Hazards Due to Specified Chemical Substances inNo. HRS contains inorganic fiber which has

November 2015, and so we could not source RCF fromexcellent heat resistance, and so can be used at

the material manufacturers. Although RCF was replaced

temperatures of up to 1,200ºC.

with biosoluble fiber（BSF）, the heat resistance of BSF③ No. HRS has less sticking to flanges than rubber-is inferior to that of RCF, and it is difficult to use BSF

coated woven fabric gaskets, so cleaning is easier.

above 1,000ºC.
To solve these challenges, VALQUA significantly
improved the sealing properties compared with those of
the conventional rubber-coated woven fabric gasket todevelop VALQUA HEAT RESIST SHEET™ No. HRS, asheet gasket which can be used at temperatures up to1,200ºC. No. HRS solves the problems of gaskets used athigh temperature and low pressure. This article
introduces the characteristics of VALQUA HEATRESIST SHEET™.
Figure1 Exterior of VALQUA HEAT RESIST SHEET™ No. HRS
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Product Introductions

White inorganic sheet4-2）Service temperature range
The service temperature ranges from −200 to 1,200ºC.

Stainless-steel thin plate

No. HRS is designed for use under low-pressureconditions including exhaust ducts. Therefore, metalgaskets and semi-metal gaskets are recommended foruse under high-pressure conditions of 1 MPa or higher.
4-3）Recommended‌tightening contact pressure andmaximum allowable tightening contact pressure
Table2 shows recommended tightening contact pressures.

Figure2

Table2

Product composition

3. Intended use
No. HRS is suitable as a sealant for places such asdevices’manholes and exhaust ducts having thefollowing characteristics：1）Although the inside fluid is
at low pressure, the flange’s strength is weak, and 2）

Recommended tightening contact pressures
Fluid

Recommended tightening
contact pressure（MPa）

Liquid20

Gas20

Note：‌The recommended tightening contact pressure is that which isnecessary under general conditions. It is set without taking
the fluid pressure into account. It is the contact pressure
regarding the gasket's contact area.

tightening force cannot be applied. Also, No. HRS can beused as a sealant for oil burners, high-temperature

5. Evaluation of characteristics

wafters, and the access doors of heat-recovery lines.

5-1）Sealing properties at room temperature

Although No. HRS has much better sealing properties

Figure3 shows the results of evaluating the sealing

than the conventional rubber-coated woven fabricproperties at room temperature. The leakage volume isgasket, it suffers greater leakage volume than sheet

1/100 or less compared with that of the conventional

gaskets including joint sheets, so care is required.

rubber-coated woven fabric gasket, showing that No.
HRS has significantly improved sealing properties. In
addition, its leakage volume is small even at tightening

4. Product specifications

contact pressures between 10 and 20 MPa. Therefore,4-1）Standard size

No. HRS provides good sealing even at locations where a

Table1 shows the standard sizes of No. HRS. Two sizes,

large tightening force cannot be applied due to the

1.5 mm and 3.0 mm in thickness, are available; theflange’s strength.

maximum outer diameter is 900 mm. Since No. HRS is a

Table1Thickness
1.5

3.0

Standard size（Unit：mm）

Maximum outer diameter
900

No. HRS Woven fabric gasket

Specimen size：JIS10K-25A t3
Internal pressure：0.2 MPa（helium）

Leakage volume（cc/min）sheet gasket, it can be processed into various shapes.

Gasket’s contact pressure（MPa）

Figure3Sealing properties at room temperature30

Summer 2018

Although the inside fluid is at low pressure, a large

No.35

Sheet Gaskets for High-Temperature Use VALQUA HEAT RESIST SHEET™ No. HRS

5-2）Heat-cycle sealing properties
The sealing properties of No. HRS were evaluated asfollows: 1）No. HRS was heated while connected to aflange. 2）The heating/cooling process was repeatedly
applied to No. HRS. 3）After cooling, the sealing
properties at room temperature were evaluated. Figure4
shows the results. No. HRS has a smaller leakage volume
than the conventional rubber-coated woven fabric gasket
even after heating, and maintains strong sealing
properties even after repeated cycles.

No. HRS
Woven fabric gasket

Specimen size：JIS10K-25A t3
Heating cycle：800℃ × 15 hours × 5 cycles
Internal pressure：0.2 MPa（nitrogen）
Tightening contact pressure：24.5 MPa
Test method for sealing property：Submersion method

Figure5

Dovetail-groove processing

We evaluated the sealing properties of gaskets with orwithout dovetail grooves. Figure6 shows the results.

Summer 2018

Leakage volume（cc/min）

Joining ① is without paste application. In Joining ② ,gasket paste No. 6M is applied to the surfaces of thejoining ends. The difference in leakage volume between
no joining and joining ① is insignificant; the twoconditions have similar sealing properties. For safer
usage, we recommend applying paste No. 6M to theBefore
heating

1stcycle

2ndcycle

3rdcycle

4thcycle

surfaces of joining ends when joining products are used.
No joining
Joining ①（Heating-cycle conditions）

Roomtemperature

Figure4Leakage volume（cc/min）

No.35

Joining ②Joining ① : 2 joined points
Joining ② : 2 joined points+ paste No. 6M was applied to the surface of the joined end.
Specimen size：JIS10K-50A t3
Internal pressure：0.2 MPa（helium）

Heat-cycle sealing properties

5-3）‌Sealing properties of joining products atroom temperature

Contact pressure（MPa）

Figure6 Sealing properties of joining products at room temperature

The maximum outer diameter of No. HRS is 900 mm.

5-4）Heat resistance

However, joining through dovetail-groove processing

To evaluate heat resistance, we evaluated the shape-（Figure5）enables No. HRS to handle products withretention characteristics after heating. Figure7 shows

larger diameters. In that case, joining is only conducted

the gaskets’appearance after heating in air at 1,000ºC

at the construction site.

and 1,200ºC. Even after heating, No. HRS had no
deformation or powdering; it kept its original shape.

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Product Introductions

Therefore, there is little risk in high-temperature usage5-6）Resistance to crushingof, for example, gasket breakage due to internal

When an excessive tightening force is applied to gaskets,pressure.

they can break. In an experiment, No. HRS wassubjected to a contact pressure of 100 MPa, as shown in

Heating time：24 hours
Atmosphere：Air
Test-use dimensions：45 mm×15 mm×t3.0

Figure9. Even after this tightening contact pressure wasapplied, the gaskets did not suffer compression fracture.
Test-use dimensions：φ100 × φ64
Loaded contact pressure：100 MPa
Crushing condition：Cracks developed

Before heatingFigure7

Results of evaluating shape retention after heating

In high-temperature environments, gaskets strongly
stick to flanges, and so time and labor are required forremoval. Figure8 shows the sticking tendency to flanges

Figure9‌Appearance of gasket after application of contactpressure of 100 MPa

after repeated heating cycles. In No. HRS, the amount ofrubber binder is reduced to the minimum, and verysmooth inorganic filler is used. Therefore, No. HRS sticks

6. Conclusion

to flanges much less than the conventional rubber-This article introduced VALQUA HEAT RESIST

coated woven fabric gasket, which facilitates flange

SHEET™ No. HRS. No. HRS has significantly better

cleaning and reduces man-hours in construction.

sealing properties and heat resistance than conventionalHeating cycle：800℃ × 15 hours × 5 cycles
Flange material：SUS316L

rubber-coated woven fabric gaskets, which have beenused for high-temperature and low-pressure applications.
This product ensures long-term safety. Some customers
have already conducted actual evaluations, and somehave already introduced No. HRS. Environmental
regulations will get stricter in future. We hope you will
use No. HRS gaskets which comply with environmental
regulations.

Satomi Takahashi
Figure8

Sticking to flanges

Summer 20185-5）Sticking tendency

Corporate Research andDevelopment Group
Product Development DivisionⅠ
32No.35