VALQUAFOIL Gasket

Making use of the characteristics of the pure graphite sealing material VALQUAFOIL™, these gaskets are excellent in heat and chemicals resistance as well as radiation resistance, and are applicable to wide temperature ranges from very low to high temperatures.

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VALQUA No.
VF-30
Product name
VALQUAFOIL Gasket
Features1
VF-30 Gasket is made by forming VALQUAFOIL™ into sheet, which is then punched into a specified flat shape.

Applicable fluids
Water, Sea water, Hot water, Steam,Crude oil, Alcohol, Animal & vegetable oil, Heat transfer oilGeneral solvent, Weak acid, Weak alkali,Strong oxidizing acid, strong alkali,Air, Nitrogen gas, Inert gas,Exhaust gas,Extremely low temperature liquids,
Inappropriate fluid
Oxidizing acids such as hot, concentrated sulfuric acid and concentrated nitric acid
Application
Type
VF-30
Remarks

■ Available ranges

Temperature（℃） Pressure（MPa）
-240〜400 2.0

1. Temperature and pressure show individual service limits. 2. Not applicable to oxidizing acids such as hot, concentrated sulfuric acid and concentrated nitric acid.

■ Dimensions

Standard dimensions Nominal thickness（mm） Standard dimensions Size（mm）
0.4 1000×1000
0.8 1000×1000
1.0 1000×1000
1.2 1000×1000
1.6 1000×1000
3.0 1000×1000

Punched gaskets can be manufactured.

■ Design criteria

Gasket factor”m” Minimum design
seating stress"y"
（N/mm2）		 Recommended
tightening stress
（MPa）Liquid		 Recommended
tightening stress
（MPa）Gas
2.0 26.0 26.0 40.0

（1） In accordance with the description in JPI-7R-70-88. （2） The recommended tightening stress is the pressures required under normal conditions, and correspond to the projected area of the gasket, where fluid pressure is not taken into consideration.

■ Characteristic values of VALQUAFOIL Gasket

■Characteristic values of VALQUAFOIL Gasket ■

Item VF-30 VF-35E（1） Remarks
Thickness（mm） 1.6 3 1.6 3 -
Tensile strength（MPa） 3.8 3.8 15.6 10.3 JIS R 3453
Compressibility
（34.3MPa） （%）		 45 43 42 42
Recovery（34.3MPa） （%） 11 12 12 13
Density（kg/m3） 1067 1054 1216 1143 -
Creep relaxation
（20.6MPa）（%） 		100℃×22h（%） 7.3 12.4 9.5 9.2 JIS R 3453
200℃×22h（%） 10.7 14.4 10.2 16.4

Note (1) Sealability Test criteria: JIS 10K50A, Internal pressure 1.0MPa, Tightening stress 25.5MPa, Thickness 1.5mm
Remarks: The above values are measured ones, and not regulatory values

■ The fluid-wise available ranges

The fluid-wise available ranges

■ Stress strain characteristics

Stress strain characteristics

■ Notes to be observed in design and usage

■ Notes to be observed in design and usage ■
▼Notes to be observed in design
・Determine the number and size of bolts and gasket dimensions to provide gaskets with sufficient tightening stress, and also check the flange construction and bolt arrangement to ensure uniform distribution of tightening stress.
・In case of considering as an alternative for Compressed Fiber Sheet, be careful about the pipe length, as the compressibility will be larger than the Compressed Fiber Sheet.
・Consideration shall be given in design to prevent application of excessive thermal stress or repetitive bending stress on the joints.
・Piping design shall not allow accumulation of drain or scale at the flange sections.

▼Notes to be observed before installation
・When installing gas seals, refer to the following"Countermeasures against permeation leakage".
・Install the gaskets in a clean environment so as to prevent entry of foreign matters between the gaskets and the flanges.
・Flange bolts No.1 to 8 as shown on the figure shall be gradually tightened in this order at a time, and repeat this process in four to five steps, so as to finally ensure uniform tightening.
・When tightening, pay attention to prevent the occurrence of crush. Especially when using gaskets of 150 Lb, 1B or smaller, or those of smaller gasket width, care shall be given as gasket stress is likely to be excessive.
・At the time of load up or restarting, check for any loose bolts.
・f retightening of gaskets that have once experienced leakage failed in preventing leakage, replace them with new ones.
・Since allowance of gasket stress is low, please pay attention to prevent crush in case of small diameter gaskets.

▼Countermeasures against permeation leakage
Since permeation leakage is prone to occur in VALQUAFOIL gasket, the following points shall be observed for gas seals:
1．Apply gasket paste on the cut surface of the gasket inner diameter side. Application of gasket paste on the contact surface between the gasket and the flange is likely to cause crush, so that careful attention is required in tightening, and also the amount of gasket paste shall be minimized.
2．Maintain the tightening stress to be around 35 MPa. Also use ring gaskets instead of full-face gaskets, so as to ensure proper tightening stress.
3．As much as possible, use gaskets with a minimum thickness (1.5 mm or less).

▼Notes to be observed in storage
・Handle these products with care, as their sheet surface is liable to be damaged.
・Store these joint sheets in a cool and dark place not subject to direct sunshine, fresh air or ozone.
・Storage selected shall be in a clean environment, free from dust as well as from high temperature & high humidity and corrosive atmosphere.
・ If hanged on nails or the like, gaskets may suffer breakage or permanent deformation, so that they should be put between larger plates and placed horizontal for storage.

■ FAQ

Q. I want to control the width of the opening in the flange such as with a sheet gasket. How should I do this?

A. Control with width of the opening in the flange is prone to cause a margin of error and an accurate tightening stress cannot be obtained. It is effective for uneven tightening, so please use it in conjunction with control of tightening torque.

Q. Please tell me about the difference in the gasket dimensions between flanges of the JPI and ASME/ANSI standards.

A. JPI basically quotes from ASME/ANSI, so there are cases in which the dimensions differ slightly due to rounding error during the millimeter conversion of the original number. We understand that, in actual use, the function of the gasket is fulfilled to an equivalent degree by both dimensions.

Q. Why does leakage occur during stop or re-operation even though there are no problems during plant operation?

A. Expansion and contraction of the flange, bolt, pipe and the like will occur due to temperature changes. As a result, a tendency of reduced tightening force in the gasket main unit is often observed when the temperature decreases (including low temperature at the time of initial re-operation), and leakage occurs due to relaxation. We therefore generally recommend a retightening of the gasket before re-operation after the first heat addition.

Q. Is retightening effective when leakage occurs?

A. Yes, it is effective. We ask that retightening during leakage be performed after relieving internal pressure. However, there are also points to keep in mind for each product, such as the possibility of damage as a result of temperature-induced hardening in the case of a compressed non-asbestos fiber sheet.

Q. I am not sure which gasket to select, so could you select it for me?

A. If you contact us together with your operating conditions, we will recommend an appropriate product based on our technician's selection.

■ VALQUA HAND BOOK TECHNICAL DATA

▶ (7)　VALQUAFOIL gasket (No. VF-30, VF-35E, VFT-30, VFT-35E)

■ VALQUA HAND BOOK DIMENSIONAL DATA

▶ （２） Rring gasket to JIS flat face flange, large raised face flange, small raised face flange
▶  （３） Rring gasket to JIS male-female flange, tongue and groove flange （table 1.1.3)
▶ （６） Rring gasket to JPI(ANSI/ASME) raised face flange （table 1.1.6)
▶ （７） Ring gasket to JPI（ANSI/ASME） male-female flange, tongue and groove flange
▶ （10） Ring gasket to JPI raised face flange for large‐bored steel pipe（table 1.1.10）

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