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7 causes of damage to the valve sealing surface

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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, cutoff, throttling, check, diversion, or overflow pressure relief. There are two reasons for the damage to the sealing surface: man-made damage and natural damage. Man-made damage is caused by factors such as poor manufacturing, improper selection of materials, improper installation, poor use, and ineffective maintenance. Natural damage is the wear of the valve under normal working conditions and the damage caused by the inevitable corrosion and erosion of the sealing surface of the medium.

Table of Contents

butterfly valve

Specifically, the main reasons for the damage to the valve sealing surface are as follows:
1. Improper installation and inadequate maintenance have caused the sealing surface to work abnormally, and the valve operates with the disease, which prematurely damages the sealing surface.
2. Damage caused by improper selection and poor operation. The main manifestation is that the valve is not selected correctly according to the working conditions, such as using the cut-off valve as a throttle valve, resulting in excessive closing specific pressure and closing too fast or not tightly, causing the sealing surface to be eroded and worn.
3. The processing quality of the sealing surface is not good, mainly manifested in the defects such as cracks, pores, and ballasts on the sealing surface, which are caused by the improper selection of surfacing and heat treatment specifications and poor handling during surfacing and heat treatment. The sealing surface is hard Too high or too low is caused by the wrong material selection or improper heat treatment. The sealing surface has an uneven hardness and is not resistant to corrosion, mainly because the underlying metal is blown to it during the surfacing process, which dilutes the alloy composition of the sealing surface Caused by. Of course, there are also design factors.
4. Mechanical damage, the sealing surface will be scratched, bumped, crushed, and other damages during the opening and closing process. Between the two sealing surfaces, under the action of high temperature and high pressure, atoms permeate and exude each other, resulting in adhesion. When the two sealing surfaces move to each other, the adhesion is easily torn. The higher the roughness of the sealing surface, the more likely this phenomenon will occur. The sealing surface of the valve will be scratched and crushed during the closing process of the valve and the valve clack during the re-seat process, causing partial wear or indentation of the sealing surface.
5. Erosion of the medium is the result of wear, washing, and cavitation on the sealing surface when the medium is moving. When the medium is at a certain speed, the floating fine particles in the medium collide with the sealing surface, causing local damage. The high-speed moving medium directly washes the sealing surface, causing local damage. When the medium is mixed and partially vaporized, gas bubbles and blasts Impact the surface of the sealing surface, causing local damage. The erosion of the medium and the alternate action of chemical erosion will strongly etch the sealing surface.
6. Electrochemical corrosion. The contact between the sealing surfaces, the contact between the sealing surface and the sealing body and the valve body, the concentration difference of the medium, the oxygen concentration, and other reasons will cause a potential difference, electrochemical corrosion will occur, and the sealing surface of the anode will be damaged. erosion.
7. The chemical corrosion of the medium, the medium near the sealing surface does not produce current, the medium directly chemically interacts with the sealing surface and corrodes the sealing surface.

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