Motor Operated Valves Torque Switch

Valve actuator - Wikipedia, the free encyclopedia

In motor operated valves there are two set of limit switches- end limit switches (CLOSE/ OPEN) and torque limit switches (CLOSE/ OPEN). The motor is supposed to stop when any one of the end limit switches get operated. However, due to either malfunction of end limit switches or motor not stopping immediately, the valve may over travel and operate the torque limit switches, whose NC contact also cuts off the motor contactor power supply. The valve may get jammed when torquue limit switch is operated. But it will prevent the valve from getting damaged.

In addition to the above, some valves are programmed to operate on torque depending on the process fluid. If there is significant solid substance in the fluid, it may be better to stop the valve on torque, rather than position, lest motoring the valve against the solid build-up should damage some part of the valve before the end-stop limit switch has operated.

Thanks PWSlack for the added information.