I am not familiar with ESD valves and new to its design. What are the factors that determine the torque requirements of ESD valve actuator? In case of emergency how the torque is taken care of? Are there any arrangements(protection) in actuator which ensures that there is no shearing of actuator in case of excess torque?An ESD valve is not some special mystery design or contraption. It is just a line spec valve with some kind of motor or pneumatic operator on it.The torque for the valve should be the same if operated manually or by motor.The main protection that should be considered for the operator is fire proofing to prevent damage and allow the valve to still function even when fully engulfed in flames. Valves have torque safety factors that can vary from 1.3 up to 2, depending on project specifications, and can also vary from Break to Open, running & End to close positions.Speed of emergency stroke operarion can also vary from 1 second total, to 1 second per inch of diameter, to 3 seconds per inch daimeter.The Safety factor has an effect on (some) valve shaft diameter, or material, due to much higher requisites (due to increase in resistance torque) as requested torques exceed valve MAST.Most of ESDV are low pressure pneumatic operated (unless you are in the desert on a gas pipeline, where line pressure= to actuator sizing pressure), by low pressure anything between 3 & 5 Barg is considered...a Air Filter Regulator should be included in instrumentation to ensure that supply pressure to actuator does not increase over sizing pressure...

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