Gear pump seal selection

Gear pump how to choose gaskets?
Gear pump seal selection principle is that, for the less demanding occasions, may be empirically selected, inappropriate replacement. But for those demanding applications, such as explosive, toxic and flammable gases and highly corrosive liquid equipment, reaction tanks and piping systems, etc., should be based on the working pressure, working temperature, the corrosiveness of the sealing medium and the sealing surface The form of choice. In general, at room temperature and low pressure, the choice of non-metallic soft gaskets; medium pressure and high temperature, the choice of metal and nonmetal combination gaskets or metal gaskets; temperature, pressure fluctuations, the choice of good elasticity Or self-tight seal; in low temperature, corrosive media or vacuum conditions, should consider the special performance of the gasket. What needs to be explained here is the influence of the flange condition on the gasket selection.
Influence of flange form. Different flanges require different spacers. Smooth surface flange is generally only used for low pressure, with a soft thin gasket; under high pressure, if the strength of the flange is sufficient, you can also use a smooth surface flange, but should be thick soft pad, or with the band to strengthen Ring or reinforcement ring wound gasket. In this case, the metal gasket is not suitable, because the pressing force required at this time is too large, resulting in greater deformation of the bolt, the flange is not easy to seal. If you want to use metal gaskets, you should shrink the smooth surface so that its contact area with the gasket is reduced. In this way, with the same bolt tension, the shrinkage stress of the reduced, narrow, smooth surface increases.
Effect of flange surface roughness. Flange surface roughness has a great effect on the sealing effect, especially when using non-soft gaskets, sealing surface roughness value is one of the major causes of leakage. For example, turning the flange surface of the knife pattern is a spiral, the use of metal gasket, if the roughness value is larger, the gasket can not be blocked by the formation of this spiral groove knife, under pressure, the media will Leaked down this groove. Soft gaskets require a much lower degree of smoothness on the flange surface because of their tendency to deform and block the tooling and thus prevent leaks. For soft gaskets, the flange surface is too smooth but unfavorable because the interface leakage resistance becomes smaller at this time. Therefore, the gasket is different, the required flange surface roughness is not the same.

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