Two main reasons for damage of sealing surface of control valve

Two main reasons for damage of sealing surface of control valve

There are two reasons for the damage of the sealing surface of the control valve: man-made damage and natural damage. Man made damage is caused by poor design, poor manufacturing, improper material selection, improper installation, poor use and poor maintenance. Natural damage is the wear of the regulating valve under normal working conditions and the damage caused by the inevitable erosion and erosion of the medium on the sealing surface. The main situations are as follows:

1、 Natural damage

1. Mechanical damage: the sealing surface will be scratched, bumped and squeezed during opening and closing. Between the two sealing surfaces, atoms permeate and exude each other under the action of high temperature and high pressure, resulting in adhesion. When the two sealing surfaces move with each other, the adhesive part can be easily pulled and torn. The higher the coarseness of the sealing surface, the easier this phenomenon occurs. During the closing process of the regulating valve and the reseating process of the valve disc, the sealing surface will be bumped and squeezed, resulting in local wear or indentation on the sealing surface.

2. Medium erosion is the result of wear, flushing and cavitation of the sealing surface of the regulating valve when the medium is active. When the medium is at a certain speed, the floating fine particles in the medium collide with the sealing surface and cause local damage. The high-speed moving medium directly washes the sealing surface to cause local damage. When the medium is mixed and partially vaporized, gas bubble blasting will impact the sealing surface and cause local damage. The alternating action of medium erosion and chemical erosion will strongly etch the sealing surface.

3. Electrochemical erosion, potential difference will occur due to the contact between the sealing surfaces of the regulating valve, the contact between the sealing surface and the enclosure and valve body, as well as the concentration difference of the medium and oxygen concentration difference, resulting in electrochemical erosion, resulting in the erosion of the sealing surface on the anode side.

4. Chemical erosion of medium: under the condition that the medium near the sealing surface of the regulating valve does not generate current, the medium directly plays a chemical role with the sealing surface and erodes the sealing surface.

2、 Man made damage

1. Improper installation and maintenance led to abnormal operation of the sealing surface of the regulating valve, defective operation of the valve and premature damage to the sealing surface.

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

3. The poor processing quality of the sealing surface of the regulating valve is mainly reflected in the defects such as cracks, pores and slag inclusion on the sealing surface, which is caused by improper selection of surfacing and heat treatment specifications and poor operation in the process of surfacing and heat treatment. The hard transition 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, It is mainly caused by blowing the bottom metal to the top in the surfacing process and diluting the alloy composition of the sealing surface. Of course, there are also design problems.