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What are the reasons for the damage to the sealing surface of the valve?
The valve is a control component in the pipeline fluid delivery system. It is used to change the passage section and the flow direction of the medium, and has the functions of diversion, cutoff, throttling, check, split or overflow relief. The cause of damage to the sealing surface is either damage or 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 of the valve under normal working conditions, and it is the damage caused by the inevitable corrosion and erosion of the sealing surface of the medium.
Specifically, the main causes of damage to the sealing surface of the valve are as follows:
One: improper installation and poor maintenance lead to the sealing surface is not working properly, the valve is running with disease, prematurely damaged the sealing surface.
Second: damage caused by improper selection and poor handling. The main performance is that the valve is not used according to the working conditions, and the shut-off valve is used as a throttle valve, which leads to the closing pressure is too large and the sealing is too fast or the sealing is not tight, so that the sealing surface is eroded and worn.
Third: the sealing surface processing quality is not good, mainly manifested in cracks, pores and pinch defects on the sealing surface, due to 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 incorrect material selection or improper heat treatment. The hardness of the sealing surface is uneven and not resistant to corrosion. The main reason is that the underlying metal is blown onto the surface during the surfacing process, which dilutes the alloy composition of the sealing surface. Caused by it. Of course, there are also design issues in it.
Four: mechanical damage, the sealing surface will cause scratches, bumps, crushing and other damage during the opening and closing process. Between the two sealing surfaces, under the action of high temperature and high pressure, atoms permeate and ooze out, resulting in blocking phenomenon. When the two sealing faces move relative to each other, the adhesion is easily pulled. The higher the roughness of the surface of the sealing surface, the easier it is. During the sealing process, the valve flap will damage and crush the sealing surface during the returning process, causing partial wear or indentation of the sealing surface.
Five: the erosion of the medium, which is the result of wear, rinsing 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 resist the sealing surface, causing local damage. The high-speed moving medium directly flushes the sealing surface to cause local damage, and when the medium is mixed and partially vaporized, the gas is blasted. Impact on the surface of the sealing surface, causing local damage. The erosion of the medium and the alternating chemical attack will strongly etch the sealing surface.
Sixth: Electrochemical erosion, contact between sealing surfaces, contact between sealing surface and enclosure and valve body, concentration difference of medium, oxygen concentration difference, etc., will cause potential difference, electrochemical corrosion will occur, causing the sealing surface of the anode side to be erosion.
Seven: chemical attack of the medium, the medium near the sealing surface does not generate current, the medium directly chemicalizes with the sealing surface, eroding the sealing surface.
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