Fail locked (last position) (FL), arrow form
ISA 5.1 (actuator action on failure)
Drawn as
A control valve with two short horizontal bars across the stem between body and actuator.
Meaning
On loss of motive power the valve stays where it was. Typical for motor-operated and double-acting valves. It is a property of the valve (set its fail action to FL), not a separate item.
Variants
- The letter form writes the letters below the body instead
- The bar forms for FL/FI come from secondary sources describing ISA 5.1 and are less widely used than the letters; check the legend
- On 3-way valves, arrows on the ports show the failed flow path
Tags
FL
Not physical hardware. Read it, then skip it in the 3D model.