What Is FC FO and FL

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Update time: 21-08-08    Views: 18000

Air to open or Air to close is an important parameter for pneumatic Control Valves, the choice between them is mainly determined by the failure position. The failure position is defined as the valve position when there is a air supply failure on site, or when the power supply fails.  According to the different action type of Pneumatic Actuators, we can divide them into the following three categories:

 

Air to open: When we supply air to the actuator , the valve is opened. Air to open is also called reverse acting actuator.

Air to close: When we supply air to the actuator , the valve is closed. Air to close is also called direct acting actuator.

Double acting: The switching actions of the actuators are all driven by the air supply, there are no springs in the double actions actuator.

 

FC: Fail To Close (Failure valve closed)

At this time, select the air to open actuator

FO: Fail To Open (Failure valve open)

At this time, select the air to close actuator

FL: Fail Lock (Failure valve locked in place)

The failure position of the electric actuator is FL,

However for Pneumatic Diaphragm Actuators need to be equipped with related accessories to achieve function of Fail Lock.

Note: Double-acting actuators do not need to be equipped with any accessories to achieve function of Fail Lock.