What are the types of commonly used flange gaskets?

The valve is used in the mineral processing plant. The pipeline necessary equipment for drying for throttling, various pipelines. But the valve flange connection is very important, it is related to the pipeline leakage of the problem, the flange link depends on whether the leak is a flange gasket.
At present, the valve commonly used flange gaskets have the following several forms, including the flange clearance is also different:
1, flexible graphite composite gasket
The middle of the flexible graphite composite gasket is 0.5mm thick carbon steel plate or stainless steel plate, the upper layer of the steel plate is covered with a flexible graphite layer, with a total thickness of about 3mm. This gasket compression has a certain resilience, and not because of the compression force is too large and lead to the destruction of the gasket, so there is a certain gap in the flange.
2, rubber asbestos gasket
The rubber asbestos gasket is suitable for low pressure and water system. The deformation of the gasket is small and the resilience is poor. If used at high temperature conditions, the bolt is affected by temperature and elongation, the gasket can not be compensated by its resilience to compensate for the gap, and only increase the pressure to keep the flange seal. The gasket is used as a seal, and the flange must have a clearance.
It is also due to the use of rubber asbestos gasket for many years, making some use of units regardless of the flange gasket material and the form of what is required to ask the flange must be a gap. In fact, it is now used in the petrochemical company process pipeline valve has basically no longer use the rubber asbestos gasket.
3, metal corrugated gasket
Metal corrugated gasket by the thickness of about 0.8mm steel by pressing or rolling on surface and formation of corrugated gasket. When the gasket is pressed, the middle flange is sealed by the deformation of the wave crest. Because the gasket is very thin, the thickness of the deformation is only about 0.5mm, so there is no obvious gap between the flange, basically belong to the no gap.
4, spiral wound gasket
In the valve link, use the winding gasket to make the flange no clearance, may appear on the outside of the gap, but there is no gap between the actual. The sealing effect of spiral wound gasket is compressed by a valve body spigot depth control and the realization of Pina gasket. The compression rate of spiral wound gaskets is generally 0.8 ~ 1.2mm. In the structural design of pressing gasket, spiral wound gasket thickness higher body spigot depth of 0.8 ~ 1.2mm, which close to the two plane flange, the gasket is in pressure and volume within the prescribed scope. In the condition, which changes with the temperature, and the gasket is reduced by bolt elongation than the pressure seal, can cushion the elasticity of compensation, so as to ensure no leakage in the flange gasket.
The amount of compression gasket can also be used bolt fastening force control, the purpose is not only to ensure that the gasket has sufficient sealing pressure and not to overload, in order to guarantee the resilience of gasket. If the fastening force does not control the bolt, and the force is too large, the gasket will lose resilience due to plastic deformation, or even destroy the gasket structure. The amount of pressure and the methods used to control the bolt screwing force to control the gasket, the structure design can give Spiralwound gasket to deformation a large degree of freedom. This structure can have flange clearance.
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