Shutdown Valves (SDV) (Normally Closed– Spring to Close) Actuator Torques

SDV Valve Start to Close Torque

Actuator Spring Start Torque - A safety factor of 100% (i.e. 2 times) should be applied on top of the valve start to close torque. This is defined as the torque at the ‘compressed spring state’ at the start of the emergency shutdown operation.

SDV Valve Reseat Torque (Valve Closing Torque)

Actuator Spring End Torque - A safety factor of 25% (i.e. 1.25 times) should be applied on top of the valve closing torque. Hence the spring should provide a torque of 1.25 times the valve closing torque at its relaxed fully closed facility emergency shutdown state.

SDV Valve Running Torque (Resistance torque)

Actuator Spring Running Torque and Air Running Torque is the Minimum Torque produced by the Actuator during the closing or opening cycle. A safety factor of 50% (i.e. 1.5 times) should be applied and maintained on top of the required valve running torque during close and open running cycles.

SDV Valve Start to Open Torque (Valve Start to Open Torque)

Actuator Air Start Torque - Pneumatic operator Start to Open torque should be 2 times the valve opening breakout torque at the start of the facility shutdown reset.

SDV Valve Reseat Torque (Valve Opening Torque)

Actuator Air End Torque - Pneumatic operator end of stroke torque should be 1.25 times the valve opening torque at the end of the opening stroke (The facility operating SDV Valve open state.

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