Functional Safety 2016

Proof testing of inhibit functions

• How to avoid the test triggering the hazard by mistake.

• Ideally test when the hazard is removed (during a shutdown)

• This is not possible when your valve is connected to an oil reservoir!

• The initiating event for the hazard itself is operator error. Do everything

possible to remove the risk of operator error during proof testing!

• Don’t test the “open inhibit” function by pressing the OPEN button and waiting

for a failure!

• Validation testing (end to end) procedure likely to be different to Operations

proof test procedure

• If the hazard cannot be removed, ensure there are at least 2 barriers

preventing the hazard