Seal is to prevent leakage, then valve manufacturers valve sealing principle is also from the prevention of leakage research. Leakage caused by the main factors of two, one is the most important factor affecting the sealing performance, that is, there is a gap between the seals, the other is the two sides of the seal between the pressure difference. Valve sealing principle is also from the liquid sealing, gas sealing, leakage channel sealing principle and valve sealing pair four aspects to analyze.
The seal of the liquid is carried out by the viscosity of the liquid and the surface tension. When a valve leaks a capillary filled with gas, the surface tension may repel the liquid or the liquid is introduced into the capillary. This creates a tangent angle. When the tangent angle is less than 90 °, the liquid will be injected into the capillary, which will cause leakage. Leakage occurs because of the different properties of the media. Test with different media, in the same condition, will come to different results. It can be used for water, air or kerosene. And when the tangent angle is greater than 90 °, leakage will also occur. Because it is related to the grease on the surface of the metal or the waxy film. Once these surface films are dissolved, the properties of the metal surface change, the original rejected liquid, will invade the wet surface, leakage. In view of the above situation, according to the Poisson formula, can reduce the capillary diameter and the medium viscosity is large, in order to prevent leakage or reduce leakage.