Oil-sealed conical plug valves, this valve seal by the sealant between the valve plug and body to achieve. The sealant is injected into the sealing surface of the valve plug and valve body by means of a check valve in the plug stem with a bolt or injection gun. In the sealing surface of the valve plug and valve body, there is storage of oil sealant quality. Therefore, when the valve is in use, the supplementary sealant can be injected through the check valve and the oil tank to effectively compensate for the lack of sealing. If the valve is not enough pre-tightening force, then the injection of sealant can not guarantee the seal, you can tighten the packing pressure bolts to increase the pre-tightening force to ensure that the seal. Similarly, the valve plug and valve sealing surface roughness value to be small, its geometric accuracy and conical valve plug and valve body taper to be accurate, in order to ensure that with a small pre-tightening force can guarantee the seal , So that the valve plug in the body of the rotation can be freely. Lubricated plug valves are particularly suitable for abrasive media as they are protected from contact with the flowing medium in the fully open position and the damaged sealing surfaces are easier to repair. Lubricated plug valves, however, should not be used for throttling because the sealant is washed away from the exposed sealing surface during throttling, so that the valve seal will be reset each time the valve is closed. This type of valve is most suitable for use on branch pipes in oil or gas fields because this pipe does not have to be pigged and the oil and gas fields contain sand and water in the media. This valve is most suitable.