Why Do Gate Valves And Globe Valves Require Upper Sealing Devices

When the valve is fully open, a sealing device that prevents the medium from leaking to the stuffing box is called an upper sealing device.

When the gate valve, Lined Globe Valve, and throttle valve are in the closed state, because the medium flow direction of the stop valve and throttle valve is from the bottom of the valve disc to the top, there is no pressure in the body cavity. When the gate valve is in the closed state, the pressure in the body cavity is lower than the working pressure, so the pressure of the medium on the packing is very small. When it is opened, the packing will be subjected to the working pressure. If there is an upper sealing structure, it can prevent the working medium pressure from acting on the sealing packing, extend the life of the sealing packing, and prevent the valve from leaking. Another function of it is that when there is leakage at the sealing packing, the valve can be fully opened to seal the upper sealing part. In this way, the packing gland or packing sleeve can be loosened, the packing can be added, and the packing gland can be tightened to ensure that the valve packing is tight and there is no leakage. Therefore, an upper sealing device must be specified for gate valves, stop valves, and throttle valves.

Of course, for valves such as ball valves, butterfly valves, check valves, and plug valves, there is no upper sealing device due to structural reasons.