Common flange gaskets and use methods in valve application
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Release Time：2017-08-16
At present, the valve commonly used flange gasket has the following forms, the flange gap is also different: 1. metal waveform gasket metal waveform gasket by the thickness of about 0.8mm of mild steel by stamping or rolling on the gasket surface and form a corrugated shape. After the gasket is compressed, the middle flange is sealed by the deformation of the wave crest. Because the gasket is very thin, its thickness is only about 0.5mm after deformation, so there is no obvious gap in the flange, which is basically no gap. 2. spiral wound gasket uses spiral wound gasket to make the flange have no gap, which may look like there is a gap on the outside, but in fact there is no gap.
At present, the valve commonly used flange gaskets have the following forms, in which the flange gap is also different:
1. Metal Wave Gasket
Metal corrugated shims are formed from mild steel having a thickness of about 0.8mm by stamping or rolling onto the surface of the shim and forming corrugations. After the gasket is compressed, the middle flange is sealed by the deformation of the wave crest. Because the gasket is very thin, its thickness after deformation is only0.5mmFor the left and right, so there is no obvious gap in the flange, basically no gap.
2. spiral wound gasket
The use of spiral-wound gaskets allows the flange to have no gap, which may appear to have a gap on the outside, but there is actually no gap. The sealing effect of the spiral wound gasket is achieved by using the depth of the valve body stop to control the compression of the gasket. The compression amount of the spiral wound gasket is generally in the structural design of the compression gasket. The thickness of the spiral wound gasket is higher than the depth of the valve body stop. When the two planes of the flange are close to each other, the compression amount of the gasket is within the specified range. Under working conditions, with the change of temperature, the sealing specific pressure at the gasket reduced by the elongation of the bolt can be compensated by the resilience of the gasket, so as to ensure that there is no leakage at the middle flange gasket. The compression amount of the gasket can also be controlled by the bolt tightening force. The purpose is to ensure that there is sufficient sealing specific pressure at the gasket without overload, so as to ensure the resilience of the gasket. If the tightening force of the bolt is not controlled and its force is too large, the gasket will lose its resilience due to plastic deformation, and even destroy the structure of the gasket. Using the method of controlling the bolt tightening force to control the pressure of the gasket, the structure design can give the winding gasket a greater degree of freedom of deformation. The middle flange of this structure may have clearance.
3. flexible graphite composite gasket
The middle of the flexible graphite composite gasket is a 0.5mm thick carbon steel plate or stainless steel plate. The upper and lower surfaces of the steel plate are covered with a flexible graphite layer, and the total thickness is about0.3mm.This gasket has a certain degree of resilience after compression, and will not cause damage to the gasket due to excessive pressing force, so there is a certain gap in the flange.
4. rubber asbestos board gasket
Rubber asbestos board gasket is suitable for low pressure and water system conditions. The deformation of this gasket is small and the resilience is poor. If it is used under high temperature conditions, the bolt is elongated under the influence of temperature, and the gasket cannot compensate for the resulting gap by its resilience, but only increases the pressing force to keep the middle flange sealed. Using this gasket as a seal, the flange must have a gap.
It is also because of the habit of using rubber asbestos board gaskets for many years that some users require flanges to have clearance regardless of the material and form of flange gaskets. In fact, now used in petrochemical enterprises on the process line of the valve has basically no longer use rubber stone body cotton plate gasket.
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