Standard for Choosing Whether Valve will be Fail Close/Open

Depends what the valve does.

It depends on your application, if it's a Nuke Core cooling valve, fail open, it's a toilet flapper valve, fail closed. What are you controlling anyhow? The application would dictate how you'd want the valve to fail, besides not wanting to fail in the first place.

There is no standard that removes responsibility or liability of an engineer to do their due diligence in designing a safe system. You want things to always fail safe. If your valve can harm people in an opened or closed failure then safety alternatives must be added to mitigate the hazard. Depending on the possible failure circumstance, mitigation can take the form of an automated evacuation warning, a second valve in series or parallel, a separate controlling system or a myriad of other system dependent safety protocols.

Depends on the process line demand . All it has consider is the Safety / Health / Environmental conditions for the People and the surroundings . Acccodingly a valve is selected for a FO or FC condition , but it has to be the FAIL SAFE condition for the situation.

There is a third possibility: fail in last position.

The HazOp Study will evaluate whether the correct selection has been made in each case.

Wonder what happen to the AP with the OP? I'm just curious to know what they're trying to control?

There is no specific standard, rather its and operational safety requirement.

Some valves need to fail ope, others closed, others last position and others do not matter.

The process / operations group defines this based on the fail safe mode of operation of the plant.