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.

機械損傷，密封面在開閉過咱中會產生擦傷、碰傷、擠傷等損壞。兩密封面之間，在高溫高壓的作用下發生原子相互滲透滲出，產生粘連現象。當兩密封面相互移動時，粘連處輕易拉撕。密封面表面粗拙度越高，這種現象越輕易發生。閥門在封閉過程中、閥瓣在回座過程中會碰傷和擠傷密封面，使密封表面局部磨損或產生壓痕。

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.

介質的沖蝕，它是介質活動時對密封面磨損、沖洗、汽蝕的結果。介質在一定的速度下，介質中的浮游細粒抵觸觸犯密封面，使其造成局部損壞，高速活動的介質直接沖洗密封面，使其造成局部損壞，介質混流和局部汽化時，產氣憤泡爆破沖擊密封面表面，造成局部損壞。介質的沖蝕加之化學侵蝕交替作用，會強烈的浸蝕密封面。

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.

電化學侵蝕，密封面互相接觸、密封面與封閉體和閥體的接觸以及介質的濃度差、氧濃差等原因，都會產生電位差，發生電化學侵蝕，致使陽極一方的密封面被侵蝕。

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.

介質的化學侵蝕，密封面附近的介質在不產生電流的情況下，介質直接與密封面起化學作用，侵蝕密封面。安裝不正和維修不力導致密封面工作不正常，閥門帶病運轉，過早地損壞了密封面。

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.