Lubricated plug valves can be divided into traditional lubricated plug valves and pressure-balanced plug valves. Special grease is injected from the top of the plug body between the valve plug hole and the plug body, forming an oil film that reduces the opening and closing torque of the valve and increases sealing and service life. The operating pressure can be up to 420 MPa, with a maximum operating temperature of 325 °C and a maximum size of 600 mm.
1. Conventional oil lubricated plug valve
A. For conventional metal-seated lubrication cone valves, the installation position of the cone plug is positive. In order to reduce the friction between the valve body and the plug sealing surface, the valve generally uses the seat sealing structure with sealing grease. The high-pressure sealing oil injected by the high-pressure oil nozzle forms a high-pressure sealing ring around the cone, that is, there is a layer of oil film between the valve body and the sealing surface of the cone , which can be sealed and lubricated and is easy to open and close.
B. To further reduce the opening and closing torque of the lubricated plug valve, the plug diameter reduction method is generally used, so the lubricated plug valve generally uses a rectangular flow path. This method increases the fluid resistance of the plug valve while reducing the opening and closing torque of the plug valve.
C. The sealing part of the spark plug cone is welded with STL alloy material or adopts surface hardening technology to improve the wear resistance and corrosion resistance of the sealing surface and ensure long service life.
D. The surface of the faucet cone is finely ground to the mirror surface, and the sealing surface of the valve body is ground, which results in lower opening and closing torque.
2. Lubricated, pressure-balanced plug valve
To reduce the torque of traditional metal-seated lubricated plug valves, pressure-balanced lubricated plug valves are often used. In addition to the features of traditional oil-lubricated plug valves, pressure balanced plug valves also have the following features:
A. The plug of the pressure-balanced lubricated plug valve is mounted in the inverted position. There is a check valve at the top of the cone. When the valve is closed, due to the difference in the upper and lower cut areas of the plug, the injected high-pressure sealing oil causes the plug body to be lifted upwards, so that the plug body and the plug surface valve seal can be better sealed.
B. At the moment the valve is opened, the pressure in the lower chamber of the valve body is equal to the average pressure in the pipeline. The high-pressure sealing oil in the upper chamber causes the plug body to be pressed downwards, and a small gap is formed between the plug cone and the sealing surface of the valve body, effectively reducing the torque of the rotating plug body. shutter.
C. At high temperatures, thermal expansion of the plug can be absorbed by raising and lowering it. For oil-lubricated plug valves, although the use of oil lubrication can reasonably reduce the opening and closing torque, it may cause contamination of the medium. Therefore, the sealed lubricant is selected according to the actual operating conditions.
