Gate valve operating torque analysis

 

Shanghai and Shanghai Engineering Valve Factory (Group) Co., Ltd.

When the opening of the gate valve is above 10%, the axial force of the gate valve, that is, the operating torque of the gate valve does not change much. When the gate valve opening is less than 10%, due to the throttling of fluid, so that before and after the gate valve pressure increases. This pressure difference effect on the gate, so that the valve stem requires a larger axial force to drive the gate, so in this range, the gate valve operating torque changes relatively large. Flexible gate valve, close to close the operating torque required to be greater than the rigid gate.

When the gate is closed, different conditions will result due to the different sealing methods of the sealing surface. For automatic sealing gate valve (including flat gate valve ), when the valve is closed, the sealing surface of the gate plate is exactly aligned with the sealing surface of the valve seat, that is, the full opening position of the gate valve. However, this position can not be monitored under the operating conditions of the gate valve. Therefore, in actual use, the position of the gate valve close to the dead center serves as the gate valve closed position. Thus, the fully closed position of the automatically sealed gate valve is determined by the position of the gate (ie, travel). For forced sealed gate valves, the gate must be closed to apply pressure to the valve seat. This pressure can ensure that the sealing surface between the gate and the valve seat is strictly sealed, is the seal force of the compulsory seal gate. This sealing force will continue to work due to the self-locking of the stem nut. Obviously, in order to provide sealing force to the gate, the stem nut transmits more torque than the valve during operation. Thus, for the mandatory seal gate valve, the fully closed position is determined by the size of the stem nut torque suffered.

Gate valve is closed, due to changes in media or ambient temperature, the expansion valve components will make the pressure between the gate and the valve seat to increase, reflected in the stem nut, to open the valve for further difficulties. Therefore, the torque required to open the gate valve is greater than the torque required to close the gate valve. In addition, for a pair of sealing surfaces in contact with each other, the coefficient of static friction between them is also greater than the coefficient of dynamic friction so that they will be relatively stationary Exercise, the need to exert greater force to overcome the static friction; due to temperature changes, so that the pressure between the sealing surface becomes larger, the static friction to be overcome also will be larger, so that when the valve is opened, the torque exerted on the stem nut Sometimes it will increase a lot.