The cylindrical plug valve is equipped with a PTFE sleeve and a valve plug seal in the valve body. The valve plug seal is pressed in the valve body by the compression nut, and the sealing effect is achieved by the expansion force of the valve plug to the PTFE sleeve.
The use of cylindrical plug valve depends on the sealing between the plug and the valve body to a certain extent. Generally, there are four commonly used sealing methods for cylindrical plug valves: sealant, plug expansion, O seal ring and PLVG seat seal ring. The sealing of cylindrical lubricated plug valves is achieved by the sealant between the valve plug and the valve body. The sealant is injected into the sealing surface by bolt or injection gun through the valve plug rod. Therefore, when the valve is in use, supplementary sealant can be injected to effectively make up for the lack of sealing.
Since the sealing surface is protected from contact with the flowing medium in the fully open position, the lubricated plug valve is particularly suitable for abrasive media. However, the lubricated cylindrical plug valve should not be used for throttling, because the sealant will be washed away from the exposed sealing surface when throttling. In this way, the sealing of the valve seat should be restored every time the valve is closed.
The disadvantage of the valve is that sealant is often needed to be added manually. Although automatic injection can overcome this problem, it increases the cost of sealant adding equipment. Once the valve lacks maintenance or the sealant is selected improperly, or crystallization is formed between sealing surfaces and the valve plug cannot rotate in the valve body, the valve must be cleaned or repaired.