With regard to the selection of new sand making machine seals, it can be selected according to experience in the case of lower requirements, and can be replaced if it is not in the market. However, for demanding applications such as explosive, highly toxic, flammable gases and corrosive liquid equipment, reactor tanks and piping systems, etc., should be based on working pressure, operating temperature, corrosiveness of the sealing medium and combined sealing surfaces. to make sure.
Generally, when the temperature is low at normal temperature, use a non-metallic sand machine soft gasket; when the medium temperature is high, use a metal or non-metal combination washer or metal washer; when the temperature and pressure fluctuate greatly, select the elasticity. Good or self-tightening gaskets; gaskets with special properties should be considered under low temperature, corrosive media or vacuum conditions. What needs to be explained here is the influence of the flange condition on the choice of the gasket.
The influence of the flange form of the sand making machine. The shape of the flange is different and the required gasket is different. Smooth surface flanges are usually only used for low pressures and have soft, thin gaskets; under high pressure, if the strength of the flange is sufficient, a smooth flange can be used, but a thick mat or a reinforcing ring in the pipe is used. Or strengthen the wrap around the gasket. In this case, the metal washer is also unsuitable because the pressure required at this time is too large, resulting in large deformation of the bolt, making the flange difficult to seal. If a metal washer is to be used, the smooth surface should be reduced to reduce the contact area with the gasket. Therefore, in the case where the bolt tension is the same, the crushing stress of the narrowed smooth surface increases.
The influence of the surface roughness of the new sand making machine flange.
The surface roughness of the flange has a great influence on the sealing effect, especially when a non-soft gasket is used, a large sealing surface roughness is one of the main causes of leakage. For example, the blade that rotates the surface of the flange is helical. When a metal gasket for a new type of sand making machine is used, if the roughness value is large, the gasket cannot block the spiral groove formed by the blade. Under pressure, the media will be stressed. Leak along the groove. Soft washers require a smoother flange surface because it is easily deformed and can hinder tooling and prevent leakage. For soft gaskets, the flange surface is too smooth and unfavorable because of the reduced interface leakage resistance. Therefore, different flanges require different flange surface roughness.