What is the purpose of the torque limit switch as fitted on an electric motor operated rising stem gate valve?

Correct Answer: Option D — The torque limit switch protects the valve from being damaged if a foreign object prevents the valve from fully closing.

Torque limit switches are safety devices designed to de-energize the motor when the valve reaches its fully seated position. If a foreign object prevents the valve from closing, the switch detects the excessive torque spike and cuts power, preventing mechanical damage to the valve stem and seat.