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Normally Closed (NC)

The term Normally Closed

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The term Normally Closed (NC) applies to manual valves or dampers which the operator must leave closed in normal operation.

A control valve which should go to closed position on control signal failure should be labeled FC, i.e. Fail Closed. 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

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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 Open (NO) - The term Normally Open

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