How to select the sealing gasket

2022-07-27
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How to select gaskets

the selection principle of sealing gasket is that for occasions with low requirements, it can be selected based on experience and replaced when it is not suitable for the market. However, for those occasions with strict requirements, such as explosive, highly toxic and combustible gases and highly corrosive liquid equipment, reaction tank and transmission pipeline system, they shall be selected according to the working pressure, working temperature, corrosivity of sealing medium and the form of combined sealing surface. Generally speaking, at normal temperature and low pressure, non-metallic soft honey sealing gasket shall be selected; In case of medium pressure and high temperature, metal and non-metal combined gaskets or metal gaskets shall be selected; In case of large fluctuation of temperature and pressure, select flexible or self tightening gasket; Under the condition of low temperature, corrosive medium or special fixture for vacuum strip to meet the actual use needs, the sealing gasket with special performance shall be considered. What needs to be explained here is the influence of flange condition on gasket selection formula

influence of flange form. Different flange types require different gaskets. Smooth face flange is generally only used for low pressure, with soft thin sealing gasket; Under high pressure, if the strength of the flange is sufficient, the smooth face flange can also be used, but the thick and soft experimental machine gasket that can meet my requirements, or the spiral sealing gasket with inner reinforcing ring or reinforcing ring should be used. In this case, the metal gasket is not applicable, because the required pressing force is too large, resulting in large deformation of the bolt, which makes the method more used in the automotive field, and it is not easy to seal. If a metal gasket is to be used, the smooth surface shall be reduced to reduce the contact area with the gasket. In this way, when the bolt tension is the same, the compression stress of the narrowed smooth surface will increase

influence of flange surface roughness. The flange surface roughness has a great influence on the sealing effect, especially when the non soft gasket is used, the large value of the sealing surface roughness is one of the main reasons for the leakage. For example, when turning the flange surface, the blade pattern is a spiral. If the roughness value of the metal gasket is large, the gasket cannot block the spiral groove formed by the blade pattern. Under the pressure, the medium will leak out along the groove. The soft gasket has much lower requirements for the smoothness of the flange surface, because it is easy to deform and can block the machining knife lines, thus preventing leakage. For soft gaskets, too smooth flange surface is unfavorable, because the interface leakage resistance becomes smaller at this time. Therefore, different gaskets require different surface roughness of flanges

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