Because seals act on the valve passages to cut off and connect, regulate and dispense, separate and mix media, etc., the seal surfaces are often subject to corrosion, erosion, and wear of the media and can easily be damaged.

The cause of damage to the sealing surface is 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 under the normal working conditions of the valve. It is caused by the inevitable corrosion and erosion of the sealing surface.

Causes of damage to the sealing surface can be summarized as follows.

Sealing surface processing quality is not good, mainly in the sealing surface cracks, pores and pinch defects such as defects, due to improper selection of surfacing and heat treatment norms and welding and heat treatment caused by poor operation, the sealing surface hardness is too high or Too low is caused by improper material selection or improper heat treatment. The uneven hardness and corrosion resistance of the sealing surface are mainly caused by blowing the bottom metal onto the surface during the welding process, diluting the alloy composition of the sealing surface. Of course, there are also design issues.

Damage caused by improper selection and operation. The main performance is that the valve is not selected according to working conditions, and the cut-off valve is used as a throttle valve, which causes the closing pressure to be too large and shutting off too fast or shutting tightly, so that the sealing surface is eroded and worn.

Improper installation and poor maintenance caused the sealing surface to work abnormally, and the valve malfunctioned, prematurely damaging the sealing surface.

The chemical corrosion of the medium, the medium around the sealing surface, in the case of no current, the medium directly acts on the sealing surface and corrodes the sealing surface.

Electrochemical corrosion, sealing surfaces contact each other, the contact between the sealing surface and the closing body and the valve body, and the concentration of the medium, the concentration of oxygen, etc., will produce a potential difference, electrochemical corrosion occurs, resulting in corrosion of the sealing surface of the anode side.

The erosion of the medium is the result of wear, erosion, and cavitation of the sealing surface during the flow of the medium. At a certain speed of medium, the floating fine particles in the medium collide with the sealing surface, causing local damage. The high-speed flowing medium directly erodes the sealing surface to cause local damage. When the medium is mixed and local vaporized, bubbles are generated by blasting and impact sealing. Face surface, causing partial damage. The erosion of the medium and the alternating effect of chemical corrosion will strongly erode the sealing surface.

Mechanical damage, the sealing surface will cause scratches, bumps, crushes and other damage during opening and closing. Between the two sealing surfaces, atomic permeation occurs under the effect of high temperature and high pressure, resulting in adhesion phenomenon. When the two sealing surfaces move to each other, the adhesion is easy to tear. The higher the surface roughness of the sealing surface, the More likely this phenomenon occurs. During the closing process of the valve, the valve flap will scratch and crush the sealing surface during the repositioning process, so that the sealing surface is locally worn or indented.

Fatigue damage, sealing surface in the long-term use, under the effect of alternating load caused by the resulting seal surface fatigue, cracking and peeling layer. After long-term use of rubber and plastic, it is prone to aging, leading to poor performance.

From the above analysis of the cause of damage to the sealing surface, we can see that to improve the quality and service life of the valve sealing surface, we must choose the appropriate sealing surface material (see material), a reasonable sealing structure and processing methods.