Valves - Normally Open (NO)
The term Normally Open (NO) applies to manual valves or dampers which the operator must leave open in normal operation.
A control valve that should go to an open position on a control signal failure should be labeled FO, i.e. Fail Open. The control signal may be pneumatic, hydraulic or electric.
• Control Valves
Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators and positioners