Blowdown Valves (BDV) (Normally Open – Spring to Open) Actuator Torques

BDV Valve Start to Open Torque

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

BDV Valve Reseat Torque (Valve Open Torque)

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

BDV Valve Running Torque (Resistance Torque)

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

BDV Valve Start to Close Torque

Actuator Air Start Torque - Pneumatic operator beginning torque should be 2 times the valve closing breakout torque at the start of the plant blowdown reset.

BDV Valve Reseat Torque (Closing Torque)

Actuator Air End Torque - Pneumatic operator end of stroke torque should be 1.25 times the valve closing torque. This is at the end of the closing stroke (The plant operating BDV Valve closed state).