Cause analysis of sealing surface damage of the ho

Cause analysis of valve sealing surface damage

because the seal plays the role of cutting off and connecting, adjusting and distributing, separating and mixing media on the valve channel, the sealing surface is often corroded, eroded and worn by the media, which is very easy to be damaged

there are two reasons for the damage of the sealing surface: man-made damage and natural damage. Man made damage is caused by factors such as poor design, poor manufacturing, improper material selection, incorrect installation, poor use and poor maintenance. Natural damage refers to the wear of the valve under normal working conditions and the inevitable corrosion and erosion of the sealing surface by the medium

the reasons for the damage of the sealing surface can be summarized as follows

the poor processing quality of the sealing surface is mainly manifested in the defects such as cracks, pores and slag inclusion on the sealing surface, which are caused by improper selection of surfacing and heat treatment specifications and poor operation in the process of surfacing and heat treatment. The hardness of the sealing surface is too high or too low, which is caused by incorrect material selection or improper heat treatment. The hardness of the sealing surface is uneven and corrosion-resistant, which is mainly caused by blowing the underlying metal onto it during surfacing, Caused by diluting the alloy composition of the sealing surface. Of course, there are also design problems

damage caused by improper model selection and poor operation. The main performance is that the valve is not selected according to the working conditions, and the block valve is used as a throttle valve, resulting in excessive closing specific pressure, too fast closing or lax closing, so that the sealing surface is eroded and worn

when the hand wheel switch is turned off and applied in the state of calibrating the machine or combining discs, it should be stopped slowly when turning the loading speed adjustment knob. Improper installation and poor maintenance lead to abnormal operation of the sealing surface, faulty operation of the valve, and premature damage to the sealing surface

chemical corrosion of the medium. Under the condition that the medium around the sealing surface does not generate current, the medium directly plays a chemical role with the sealing surface and corrodes the sealing surface

electrochemical corrosion, the contact between the sealing surfaces, the contact between the sealing surface and the closing body and the valve body, as well as the concentration difference of the medium and oxygen concentration difference, will produce potential difference and electrochemical corrosion, resulting in the corrosion of the sealing surface on the anode side

the erosion of the medium is the result of the wear and erosion of the sealing surface when the medium flows. 2. The working principle and cavitation of the film pendulum impact tester. 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 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 effect of medium erosion and chemical corrosion will strongly etch the sealing surface

mechanical damage. The sealing surface will be scratched, bumped, crushed and other damage during opening and closing. Between the two sealing surfaces, atoms penetrate each other under the action of high temperature and high pressure, resulting in adhesion. When the two sealing surfaces move with each other, the adhesion is easy to tear. The higher the surface roughness of the sealing surface, the easier this phenomenon occurs. During the closing process of the valve and the reseating process of the valve disc, the sealing surface will be bruised and crushed, causing local wear on the sealing surface. In the confrontation between the skill needs, we seek the tension that can meet various specific needs at the same time, which reduces the angle of the wedge or produces indentation

fatigue damage. In the long-term use of the sealing surface, under the action of alternating load, the sealing surface has fatigue, cracks and delamination. After long-term use, rubber and plastics are prone to aging, resulting in poor performance

from the above analysis of the reasons for the damage of the sealing surface, it can be seen that in order to improve the quality and service life of the valve sealing surface, appropriate sealing surface materials (see the material part), reasonable sealing structure and processing methods must be selected