Motorised Operated Valve

Let me re-phrase the question for other forum readers.

An MOV is a motor operated valve. Rotork is a vendor a electric actuators. Their market tends to be large actuators (as opposed to small HVAC actuators), some models with multiple horsepower electric motors.

Why would one want to know (torque limit switch) that there is an excessive torque being applied to a valve from its electric actuator?

Hmmmmm

It limits the torque that the motor produces. That should be obvious to even the most casual observer.

Read the owners manual.

As already said torque switch (TS) trips when the torque needed to move the valve reach an adjustable value.

It can be used to regulate the amount of torque (rotary shafts or stems) or thrust (raising stem valves) when the valve seat or to overcome the maximum requirement at any other position due to the system and valve characteristics (size, pressure differential, flow rate...). It is used as a protection device too, as for valves with no seating force required, if they are regulated by limit switches and something obstructs the valve stroke, then the TS trips the actuator before the actuator itself or the valve get damaged.

One more thing, even we all name it "torque switch", normally are switches tripped by the linear displacement of a Belleville spring pack.

In addition to other's comment, this comment http://cr4.globalspec.com/comment/735004 from an earlier thread will help you to get the answer.

- MS

I have a number of Rotork valve actuators.

The most common way to set them up is to use the torgue limit on the closiing action. This limits the force the actuator applies to the valve when seating.

This setting protects the valve seat, the actuator motor and makes sure the actuator has enough force to open the valve.

Use the limit switch for the opening action this allows full power to open the valve and then stops the motor at a pre- determined position.