The valve is a pipeline accessory used to open and close the pipeline, control the flow direction, adjust and control the parameters (temperature, pressure and flow) of the transmission medium. From simple stop valves to various valves used in extremely complex automatic control systems, they have a wide variety and specifications. The nominal diameter of valves ranges from very small instrument valves to industrial pipeline valves with a diameter of 10m. During the use of the valve, the sealing surface of the valve is often damaged, and internal leakage will occur if it is damaged. Why does this happen? There are many aspects to understand here. Let's take a look.

机械损伤，密封面在开闭过咱中会产生擦伤、碰伤、挤伤等损坏。两密封面之间，在高温高压的作用下发生原子相互渗透渗出，产生粘连现象。当两密封面相互移动时，粘连处轻易拉撕。密封面表面粗拙度越高，这种现象越轻易发生。阀门在封闭过程中、阀瓣在回座过程中会碰伤和挤伤密封面，使密封表面局部磨损或产生压痕。

Mechanical damage: the sealing surface will be scratched, bumped and squeezed during opening and closing. Between the two sealing surfaces, atoms permeate and exude each other under the action of high temperature and high pressure, resulting in adhesion. When the two sealing surfaces move with each other, the adhesive part can be easily pulled and torn. The higher the coarseness of the sealing surface, the easier this phenomenon occurs. During the sealing process of the valve and the reseating process of the valve disc, the sealing surface will be bumped and squeezed, resulting in local wear or indentation on the sealing surface.

介质的冲蚀，它是介质活动时对密封面磨损、冲洗、汽蚀的结果。介质在一定的速度下，介质中的浮游细粒抵触触犯密封面，使其造成局部损坏，高速活动的介质直接冲洗密封面，使其造成局部损坏，介质混流和局部汽化时，产气愤泡爆破冲击密封面表面，造成局部损坏。介质的冲蚀加之化学侵蚀交替作用，会强烈的浸蚀密封面。

Medium erosion 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 and cause local damage. The high-speed moving medium directly washes the sealing surface to cause local damage. When the medium is mixed and partially vaporized, gas bubble blasting will impact the sealing surface and cause local damage. The alternating action of medium erosion and chemical erosion will strongly etch the sealing surface.

电化学侵蚀，密封面互相接触、密封面与封闭体和阀体的接触以及介质的浓度差、氧浓差等原因，都会产生电位差，发生电化学侵蚀，致使阳极一方的密封面被侵蚀。

Electrochemical erosion, the contact between sealing surfaces, the contact between sealing surface and closure body and valve body, as well as the concentration difference of medium and oxygen concentration difference, will produce potential difference and electrochemical erosion, resulting in the erosion of the sealing surface on the anode side.

介质的化学侵蚀，密封面附近的介质在不产生电流的情况下，介质直接与密封面起化学作用，侵蚀密封面。安装不正和维修不力导致密封面工作不正常，阀门带病运转，过早地损坏了密封面。

Chemical erosion of the medium. When the medium near the sealing surface does not generate current, the medium directly acts with the sealing surface to erode the sealing surface. Improper installation and maintenance led to abnormal operation of the sealing surface, faulty operation of the valve and premature damage to the sealing surface.