Metal Jacketed Gasket

Metal Jacketed Gasket is composed of carefully selected cushion materials such as non-asbestos millboard, ceramic fiber, compressed non-asbestos sheet and PTFE sheet with external metal jacket of carbon steel, stainless steel, copper, etc. They are widely used on piping flanges, joints of machinery and heat exchangers because they can be fabricated not only to a regular round shape but also to other irregular shapes such as oval, rectangular, etc. with additional partition or partitions to seal multi-pass heat exchangers. An increased demand has recently been seen for a special type having attached expanded graphite tapes on both sealing faces to increase sealability.

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VALQUA No.
N520-C
Product name
Metal Jacketed Gasket (Grommet type)

Features1
Cut surface on the inner diameter side of sheet gaskets made of Compressed Fiber Sheet and the like is covered with a thin metallic sheet (grommet-finished), which contributes to permeation leakage prevention and erosion prevention.
Features2
Non-asbestos board cannot be used.

Applicable fluids
Water, Sea water, Hot water, Steam,Crude oil, Alcohol, Animal & vegetable oil, Heat transfer oilGeneral solvent, Weak acid, Weak alkali,Air, Nitrogen gas, Inert gas,Exhaust gas,など
Inappropriate fluid
Application
Dimensions
Any forms are available. As for dimensions, products with amaximum diameter of about 3,000 mm can be manufactured,while still larger ones may also be fabricated at site upon request. No.520-C, limiting dimensions depend on core materials used.
Type
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Remarks
Gasket paste (seal paste or No.6M) shall be used in principle. Flange surface shall be finished as 1.6a.

■ Available ranges

Temperature(℃) Pressure(MPa)
Depending on core material
Depending on core material

■ Design criteria

For No.520-C, the m, y values of core materials are applied.

The recommended tightening stress are the pressures required under normal conditions, and correspond to the projected area of the gasket, where fluid pressure is not taken into consideration.

The minimum design seating stress "y" correspond to values obtained when applied with gasket paste.

■ Maximum service temperatures for gasket metallic materials (for reference)

■Maximum service temperatures for gasket metallic materials (for reference)■

Material Maximum service temperature (℃)
Lead 100
Brass 260
Aluminum 260
Copper 400
SUS304 427
SUS316 816
Pure iron 538
Low-carbon steel 538
Titanium 1,093

Material Maximum service temperature (℃)
5Cr-0.5Mo steel 621
SUS410 649
Silver 649
Nickel 760
Monel metal 816
SUS321 816
SUS347 816
Inconel 1,093
Hastelloy 1,093

Remarks Since the above maximum service temperatures are based on air with a certain constant temperature, they vary to a great extent depending on the type of liquid, pressures and mode of use.

■ Upon placing order

■ 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

■ VALQUA HAND BOOK DIMENSIONAL DATA


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