Normally Open (NO)

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The term Normally Open (NO) applies to manual valves or dampers which the operator must leave open in normal operation.

A control valve which should go to the open position on control signal failure should be labeled FO, i.e. Fail Open. The control signal may be pneumatic, hydraulic or electric.

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Related Topics

• Control Valves - Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators and positioners

Related Documents

• Fail Closed (FC) - A control valve which should go to closed position on control signal or air failure would be labeled FC
• Fail Last (FL) - A control valve which should stay put on control signal or air failure would be labeled FL
• Fail Open (FO) - A control valve which should go to the open position on control signal or air failure should be labeled FO
• Normally Closed (NC) - The term Normally Closed