After the carbon steel gate valve packing is installed in the stuffing box, axial pressure is applied to it by the gland. The shaping of the filler causes it to generate radial forces and is in close contact with the valve stem, but not quite uniform. When the valve is running, there will be relative movement between the stem and the packing. Under the influence of high temperature, high pressure and strong permeability medium, the stuffing box will leak.
Carbon steel gate valve should avoid the use of negative pressure in the pipe, if there is negative pressure, it is easy to cause the valve inner cavity fluoroplastic layer was sucked out (bulging out), shelling, resulting in the valve opening and closing failure. Pressure, pressure difference should be controlled within the allowable range. Especially the bellows sealed fluoroplastic control valve, globe valve. Because the corrugated tube is made of PTFE, the pressure and pressure difference are large, which easily causes the bellows to break.