1, the sealing surface processing quality is not good. The main performance in the sealing surface of cracks, pores and slag and other defects, is due to the improper selection of surfacing and heat treatment and the process of surfacing and heat treatment caused by poor operation; The sealing surface hardness is too high or too low, is due to improper selection of materials or heat treatment caused by inappropriate, the sealing surface hardness unevenness, non-corrosion, The main reason is that the bottom metal is blown to the top in the surfacing process, and the alloy composition of the sealing surface is diluted. Of course, there are problems with design.
2, improper modeling and bad operation of the damage. The main performance in the absence of the operating conditions of the selection of valves, the cut-off valve when the throttle valve, resulting in close than the pressure is too large and close too fast or close, so that the sealing surface by erosion and wear.
3, the installation is not correct and poor maintenance caused the sealing surface work is not normal, the valve operation, premature damage to the sealing surface.
4, the chemical corrosion of the medium. The media around the sealing surface does not produce current, the media directly with the sealing surface chemical action, corrosion sealing surface.
5. Electrochemical corrosion. Sealing surface contact with each other, the sealing surface and the valve body contact and the medium concentration difference, oxygen concentration and other reasons, will produce potential difference, electrochemical corrosion, resulting in the anode side of the sealing surface is corroded.
6, the media erosion. It is the result of abrasion, scour and cavitation of the sealing surface when the medium is flowing. Medium at a certain speed, the medium of the floating fine particles impact the sealing surface, causing the local damage, the high-speed liquid media directly scour the sealing surface, causing it to cause local damage, mixed media and local vaporization, the bubble blast impact sealing surface, resulting in local damage. The condition of the medium combined with the alternating effect of chemical corrosion, the sealing surface will be strongly etched.
7, mechanical damage. The sealing surface in the opening and closing process will produce abrasions, bumps, injuries and other damage. Between the two sealing surfaces, the atom penetrates under the action of high temperature and high pressure, resulting in adhesion, when two sealing surfaces move with each other. The adhesion is easy to pull and tear. The higher the surface roughness of the sealing surface, the more easily this phenomenon occurs. Valve in the process of closing, the disc in the back of the process will be bruised and crush the sealing surface, so that the sealing surface of local wear or indentation.
8, fatigue damage. In the long-term use of the sealing surface, under the action of alternating load, the sealing surface produces fatigue, and cracks and stripping layers occur. Rubber and plastics are prone to aging due to their long-term use, resulting in poor performance.