The valve is a control component in the pipeline fluid conveying system. It is used to change the passage section and the flow direction of the medium. It has the functions of diversion, cut-off, throttling, check, shunt or overflow and pressure relief. There are two reasons for the damage of the sealing surface: man-made damage and natural damage. Man-made damage is caused by factors such as poor design, poor manufacturing, improper material selection, improper installation, poor use and poor maintenance. Natural damage is the wear and tear of the valve under normal working conditions, and it is the damage caused by the inevitable corrosion and erosion of the sealing surface by the medium. Specifically, the main reasons for the damage to the sealing surface of the valve are as follows: 1. Improper installation and poor maintenance lead to abnormal operation of the sealing surface, and the valve operates in a diseased manner, which prematurely damages the sealing surface. 2. Damage caused by improper selection and poor manipulation. It is mainly manifested in that the valve is not selected according to the working conditions, and the shut-off valve is used as a throttle valve, which leads to excessive closing pressure and fast closing or poor closing, which causes the sealing surface to be eroded and worn. 3. The processing quality of the sealing surface is not good, mainly manifested in defects such as cracks, pores and ballast on the sealing surface, which are caused by improper selection of surfacing and heat treatment specifications and poor manipulation during surfacing and heat treatment. Too high or too low is caused by wrong material selection or improper heat treatment. The hardness of the sealing surface is uneven and it is not resistant to corrosion, mainly because the underlying metal is blown onto it during the surfacing process, which dilutes the alloy composition of the sealing surface. caused by. Of course, there are also design issues here. 4. Mechanical damage, the sealing surface will be scratched, bumped, crushed and other damage during the opening and closing process. Between the two sealing surfaces, under the action of high temperature and high pressure, the mutual penetration and exudation of atoms occurs, resulting in the phenomenon of adhesion. When the two sealing surfaces move to each other, the adhesion is easily pulled and torn. The higher the roughness of the sealing surface, the easier this phenomenon occurs. During the closing process of the valve, the valve disc will bump and squeeze the sealing surface during the process of returning to the seat, causing partial wear or indentation of the sealing surface. 5. Erosion of the medium, which is the result of wear, flushing and cavitation of the sealing surface when the medium is active. When the medium is at a certain speed, the floating fine particles in the medium collide with the sealing surface, causing local damage, and the high-speed moving medium directly washes the sealing surface, causing local damage. Impact the sealing surface, causing local damage. The erosion of the medium and the alternating action of chemical erosion will strongly erode the sealing surface. 6. Electrochemical erosion, the contact of the sealing surfaces with each other, the contact between the sealing surface and the sealing body and the valve body, and the concentration difference of the medium, the oxygen concentration difference, etc., will cause a potential difference, electrochemical erosion, and cause the sealing surface on the anode side to be damaged. erosion. 7. Chemical erosion of the medium, the medium near the sealing surface will directly act chemically with the sealing surface without generating current, eroding the sealing surface.