Due to the functions of sealing elements on the valve channel, such as cutting and connecting, adjusting and distributing, separating and mixing media, the sealing surface is often corroded, eroded, and worn by the media, making it highly susceptible to damage.
There are two reasons for damage to the sealing surface: artificial damage and natural damage. Human damage is caused by factors such as poor design, poor manufacturing, improper material selection, improper installation, poor use, and poor maintenance. Natural damage refers to the wear and tear of the valve under normal working conditions, as well as the inevitable corrosion and erosion of the sealing surface caused by the medium.
1. Poor processing quality of sealing surface
The main manifestations are cracks, pores, and slag inclusions on the sealing surface, which are caused by improper selection of welding and heat treatment specifications, as well as poor operation during the welding and heat treatment process. The hardness of the sealing surface is too high or too low, which is caused by improper material selection or heat treatment. The hardness of the sealing surface is uneven and not corrosion-resistant, mainly due to blowing the underlying metal onto it during the welding process, Caused by diluting the alloy composition of the sealing surface. Of course, there are also design issues involved.
2. Damage caused by improper selection and poor operation
The main manifestation is that the valve was not selected according to the operating conditions, and the block valve was used as a throttle valve, resulting in excessive closing pressure, too fast closing, or lax closing, resulting in erosion and wear on the sealing surface.
Incorrect installation and poor maintenance resulted in abnormal operation of the sealing surface, valve operation with defects, and premature damage to the sealing surface.
3. Chemical corrosion of media
The medium around the sealing surface, without generating current, directly reacts with the sealing surface and corrodes it. Electrochemical corrosion occurs due to factors such as mutual contact between sealing surfaces, contact between sealing surfaces and the closure body and valve body, as well as differences in medium concentration and oxygen concentration, which can lead to potential differences and electrochemical corrosion, resulting in corrosion of the sealing surface on the anode side.
4. Erosion of media
It is the result of wear, erosion, and cavitation of the sealing surface when the medium flows. At a certain speed, the floating fine particles in the medium collide with the sealing surface, causing local damage. The high-speed flowing medium directly washes the sealing surface, causing local damage. When the medium is mixed and partially vaporized, bubbles explode and impact the sealing surface, causing local damage. The alternating action of medium erosion and chemical corrosion will strongly erode the sealing surface.
5. Mechanical damage
The sealing surface may be damaged by scratches, bumps, and squeezing during opening and closing. Under the action of high temperature and pressure, atoms penetrate each other between the two sealing surfaces, resulting in adhesion. When the two sealing surfaces move towards each other, the adhesive area is prone to tearing. The higher the surface roughness of the sealing surface, the easier this phenomenon is to occur. During the closing process of the valve and the reseating process of the valve disc, the sealing surface may be damaged and squeezed, causing local wear or indentation on the sealing surface.
6. Fatigue damage
During long-term use, the sealing surface may experience fatigue, cracks, and delamination under alternating loads. After long-term use, rubber and plastic are prone to aging, leading to poor performance.
From the analysis of the causes of damage to the sealing surface above, it can be seen that in order to improve the quality and service life of the valve sealing surface, it is necessary to choose appropriate sealing surface materials, reasonable sealing structures, and processing methods.
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