Time of publication:

2023-11-06

Because the seal plays a role in cutting off and connecting, adjusting and distributing, separating and mixing the medium in the flow channel of the valve, the sealing surface is often corroded, eroded, worn and easily damaged by the medium. Sealing surface damage is caused by man-made damage and natural damage. Man-made damage is caused by improper design, poor manufacturing, improper material selection, improper installation, improper use, poor maintenance and other factors. Natural damage refers to the wear of the valve under normal working conditions, as well as the inevitable corrosion and erosion of the sealing surface caused by the medium. The reasons for the damage of the sealing surface are summarized as follows: The poor processing quality of the sealing surface is mainly manifested in defects such as cracks, pores and fixture design of the sealing surface. The hardness of the sealing surface is too high or too low due to improper selection and specification of surfacing and heat treatment during surfacing and heat treatment operations. The hardness of the sealing surface is uneven and corrosion resistant due to material errors or heat treatment failure. The main reason is that the bottom metal is blown to the top during surfacing, diluting the alloy composition of the sealing surface. Of course, there are also design issues. Damage caused by improper selection and improper operation. The main performance is not selected according to the working conditions of the valve, the throttle valve using cut-off valve, resulting in the closing pressure is too large, close too fast or too loose, so that the sealing surface is eroded and worn. Improper installation and improper maintenance can cause abnormal operation of the sealing surface, abnormal valve operation, and premature damage to the sealing surface. Chemical corrosion of the medium, the medium in the case of no current around the sealing surface, the medium directly and the sealing surface of the chemical interaction, corrosion of the sealing surface. Electrochemical corrosion, sealing surface contact, sealing surface contact with the closed body and valve body, as well as medium concentration difference, oxygen concentration difference and other reasons, will produce potential difference, electrochemical corrosion, resulting in the anode side of the sealing surface is corroded. Media erosion is the result of wear, erosion and cavitation of the sealing surface when the medium flows. Medium at a certain speed, the medium of the plankton particles impact the sealing surface, causing local damage, high-speed flow of the medium directly scour the sealing surface, causing local damage, medium mixed flow and local vaporization, bubble explosion impact sealing surface, causing local damage. The alternating action of dielectric erosion and chemical corrosion will strongly corrode the sealing surface. When mechanically damaged, the sealing surface will cause scratches, scratches, extrusion and other damage to the za when it is opened and closed. Between the two sealing surfaces, under the action of high temperature and high pressure, atoms penetrate each other, resulting in adhesion. When the two sealing surfaces move relative to each other, the adhesive force tends to tear. The higher the surface roughness of the sealing surface, the greater the possibility of this phenomenon. In the process of closing the valve, the valve in the process of returning to the valve seat will encounter and squeeze the sealing surface, so that the sealing surface of local wear or depression. Fatigue damage, the sealing surface in long-term use, the three fine valves under the action of alternating load lead to sealing surface fatigue, cracks and peeling layer. After long-term use, rubber and plastics are prone to aging, resulting in poor performance. From the above analysis of the causes of damage to the sealing surface, it can be seen that in order to improve the quality and service life of the valve sealing surface, it is necessary to select the appropriate sealing surface material and reasonable sealing structure and processing methods.