1. Gasket leakage

Generally, there are four forms of leakage of gaskets: interface leakage, penetration leakage, diffusion leakage, and destruction leakage.

interface leak

Leakage will occur on the sealing interface due to insufficient compression of the gasket, improper finish of the flange joint surface, and deformation of the flange. For the interface leakage, it can be prevented by clamping it in the flange surface with soft padding.

penetration leakage

Since most soft materials are made of fibers, they are easily infiltrated by media, especially under pressure. Due to the capillary phenomenon, the medium will penetrate to the low pressure side, forming infiltration.

Diffusion leak

Driven by the concentration difference, the medium passes through the sealing gap or the capillary of the sealing material to produce leakage. Diffusion is the result of molecular motion and is not unidirectional. In the case of extremely small sealing pressure difference or vacuum state, or when sealing nitrogen, hydrogen and other permeable substances, as well as highly toxic and radioactive substances, special attention should be paid to two kinds of leakage, penetration and diffusion.

sabotage leak

The working conditions in the sealing part are relatively harsh, the thermal deformation is large, and it is often subjected to vibration, shock, improper installation, excessive fastening force, repeated use, compression deformation, internal stress concentration, damage beyond the fatigue strength, material aging, deterioration, etc. Both will cause damage to leakage. This kind of leakage has the greatest impact and great harm, so precautions must be strengthened.

2. Gasket sealing mechanism

The function of the gasket is generated by the blocking effect on the internal medium formed by the contact pressure of the sealing material on the joint surface and the elastic recovery force on the fastening external force.

3. The classification and structure of the gasket

Gaskets are divided into three categories: non-metallic gaskets, non-metallic and metal combined gaskets and metal gaskets. The common materials are rubber, leather, asbestos board, cork, polytetrafluoroethylene, tinplate, steel, aluminum, copper and stainless steel etc.

4. Selection of gasket

The selection principle of the gasket: choose according to the working pressure, working temperature, corrosiveness of the sealing medium and the form of the combined sealing surface.

       temperature effect

At normal temperature and low pressure, use non-metallic soft gaskets; at medium pressure and high temperature, use metal and non-metal composite gaskets or metal gaskets; when temperature and pressure fluctuate greatly, choose elastic or self-tightening seals Gaskets; under low temperature, corrosive media or vacuum conditions, gaskets with special properties should be considered.

Influence of flange form

Different types of flanges require different gaskets. Smooth surface flanges are generally only used for low pressure and are equipped with soft thin gaskets; under high pressure, if the strength of the flange is sufficient, smooth surface flanges can also be used, but thick soft gaskets should be used, or inner reinforced gaskets should be used. Wound gaskets for rings or reinforcing rings. In this case, metal gaskets are also not suitable, because the required pressing force is too large at this time, resulting in large deformation of the bolts, making the flange difficult to seal tightly. If a metal gasket is used, the smooth surface should be reduced to reduce the contact area with the gasket. In this way, under the same bolt tension, the compressive stress of the reduced narrow smooth surface will increase.