Valve sealing surface damage cause valve manual butterfly check valve

Valve sealing surface damage cause valve manual butterfly check valve

Due to the sealing in the valve channel plays a truncation and access, regulation and distribution, separation and mixing of media, so the sealing surface is often subjected to corrosion, erosion, wear, easy to damage.
The cause of sealing surface damage is human damage and natural damage. Artificial 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 and tear of the valve under normal working conditions, and the damage caused by the inevitable corrosion and erosion of the sealing surface by the medium.
The causes of sealing surface damage can be summarized as follows.
Sealing surface machining quality is bad, mainly displays in the sealing surface defects such as cracks, porosity and clamp design, is due to improper selection and overlaying welding and heat treatment specification in the process of the overlaying welding and heat treatment operation, caused by the bad sealing surface hardness is too high or too low, is due to failure of wrong material or heat treatment, sealing surface uneven hardness, corrosion resistance, 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 design issues.
Damage caused by improper selection and operation. The main performance is that the valve is not selected according to the working conditions, and the cut-off valve is used as the throttle valve, which leads to too high closing specific pressure and too fast closing or lax closing, so that the sealing surface is eroded and worn.
Improper installation and poor maintenance lead to abnormal work of the sealing surface, and the valve operates with disease, which damages the sealing surface prematurely.
Chemical corrosion of the medium, the medium around the sealing surface in the case of no current, the medium directly plays a chemical role with the sealing surface, corrosion of the sealing surface.
Electrochemical corrosion, sealing surface contact with each other, sealing surface and closed body and valve body contact, medium concentration difference, oxygen concentration difference and other reasons, will produce potential difference, electrochemical corrosion, resulting in the anode side of the sealing surface corrosion.
The erosion of the medium is the result of abrasion, erosion and cavitation of the sealing surface when the medium flows. Medium at a certain speed, the fine particles in the medium impact the sealing surface, so that it causes local damage, high-speed flow of medium directly scour the sealing surface, so that it causes local damage, medium mixed flow and local vaporization, bubble blasting impact on the surface of the sealing surface, causing local damage. The erosion of the medium and the alternating effect of chemical corrosion will strongly erode the sealing surface.
Mechanical damage, sealing surface in the opening and closing of the US will produce abrasion, bump, squeeze and other damage. Between the two sealing surfaces, under the action of high temperature and high pressure, atoms penetrate into each other, resulting in adhesion phenomenon. When the two sealing surfaces move each other, the adhesion is easy to tear. The higher the surface roughness of the sealing surface, the more likely this phenomenon is to occur. Valve in the closing process, the valve disc in the process of returning to the seat will hurt and squeeze the sealing surface, so that the sealing surface local wear or indentation.
Fatigue damage, sealing surface in long-term use, under the action of alternating load caused the sealing surface fatigue, crack and peeling layer. Rubber and plastic after long-term use, easy to produce aging phenomenon, resulting in poor performance.
From the above analysis of sealing surface damage causes, it can be seen that to improve the quality and service life of the valve sealing surface, it is necessary to choose appropriate sealing surface materials (see material section), reasonable sealing structure and processing methods.
Butterfly CHECK valve The butterfly check valve is opened by the pressure of the medium to overcome the torsion force of the spring, and closed by the torsional moment produced by the spring, and then by the pressure of the medium to produce the sealing pressure to seal. In use, attention should be paid to whether there is abnormal sound and vibration of the valve. In order to prevent the formation of water hammer effect in the pipeline, attention should be paid to the fluctuation of pipeline medium pressure. Long – term storage of the valve should be regularly inspected, *** dirt. Special attention should be paid to the cleaning of the sealing surface to prevent the damage of the sealing surface. Before installation, carefully check whether the valve mark is in accordance with the use requirements.
Range of 1.
This manual includes nominal diameter DN15mm~1000mm(1/2″~4″), nominal pressure
PN1.6 MPa ~ 10 MPa (ANSI >
2. Use
2.1 The valve is used in pipes or devices to prevent media backflow.
2.2 Select the material of the valve according to the medium.
2.2.1 Carbon steel valve is suitable for water, steam, oil and other media.
2.2.2 Stainless steel valves are suitable for corrosive media.
2.3 Applicable temperature:
2.3.1 The applicable temperature of ordinary carbon steel valve is -29℃+425℃
2.3.2 Alloy steel valve applicable temperature -29℃~550℃
2.3.3 The applicable temperature of stainless steel valve is -196℃~+200℃
Structure of 3.
3.1 Basic structure of butterfly check valve is shown in Figure 1
4. How it works
The BUTTERFLY CHECK VALVE IS OPENED BY THE PRESSURE OF THE medium to overcome the TORsional force of the spring, and closed by the TORsional moment produced by the spring, and then by the pressure of the medium to produce the sealing pressure to seal.
5. Storage, maintenance, installation and use
5.1 The valve shall be stored in a dry and ventilated room, and both ends of the valve passage shall be blocked.
5.2 Valves stored for a long time should be inspected regularly for dirt. Special attention should be paid to the cleaning of the sealing surface to prevent the damage of the sealing surface.
5.3 Before installation, carefully check whether the valve mark is in accordance with the use requirements.
5.4 Before installation, the inner chamber and sealing surface of the valve should be checked. If there is dirt, it should be cleaned with a cleaning cloth.
5.5 Before installation, it should be noted that the flow direction mark on the valve is consistent with the flow direction of the medium.
5.6. Butterfly check valves can be installed either vertically or horizontally, depending on pipeline conditions.
5.7 During use, attention should be paid to whether there is abnormal sound and vibration of the valve. In order to prevent the formation of water hammer effect in the pipeline, attention should be paid to the fluctuation of pipeline medium pressure.
6. The possible faults, causes, and elimination methods are shown in Table 1
Table 1 Possible faults, causes, and troubleshooting methods
The warranty of 7.
The manufacturer is responsible for the warranty of the valve within one year after it is put into use, but not more than 18 months after delivery. During the warranty period, due to product quality reasons can be repaired or replaced.
Flanged connection butterfly check valve