Published by: Valve Test Bench Technology Wedge gate valves open and close the valve torque characteristics of the basics in Figure 1-21 below. Curve can be seen from the figure, when the valve opening 10% or more, the gate of the axial force, that is, under the pressure difference across the valve open and close torque change little. When the valve's opening is less than 10%, due to throttling, so that increased pressure around the valve, the pressure acting on the gate, so that stem axial force required to propel a large gate open and close . Thus, in some areas, the gate's open and close torque change is relatively large. The figure, the actual gate valve of the headstock, said rigid torque characteristics; dotted lines indicate the elasticity of the valve gate to open and close torque characteristic. Be seen from the curves, flexible gate of the valve, near the close of the headstock torque required to be bigger than the rigid gate. Closure of the gate valve 10, the need to gate sealing force applied to the valve seat, the preload force, including sealing and media pressure, the sealing force can guarantee that gate and the seat sealing surface between the rigid seal. The sealing force due to the self-locking stem thread and media pressure will continue the role. Clearly, in order to provide sealing damper force, stem nut torque transmission torque than the gate of the headstock to be large, we can see that gate's closed position is based on stem nut torque suffered by the size determined.