PetroStreet

Once performing risk assessment, we lock certain assets as mitigations like in many of the scenarios, a pressure safety valve. That means we always consider this PSV to be available in healthy condition. However, if not marked property or locked or identified in some system, PSV preventive maintenance may get overdue and it can no more be considered as an available motigation. How to best control such a scenario?

What we have been doing at our place is identifying such mitigations and ensuring that they are kept in a critical equipment register, all logged in.
Whenever, there is any failure of such identified critical equipment register, associated systems are risk assessed again till the identified mitigations are brought back in service.
That register is with Operations and I am not quite sure about its maintenance.

It is one of the most challenging area of risk assessment. Yes, you define the controls & mitigations but now who would be responsible to make sure they are applied and stay healthy for the intended time.
System tagging & locking can help however, you still cannot control a corrective /preventive maintenance call of that particular mitigated tag. And for that particular time period, you may need to perform a new risk assessment. One thing what we can do as a team is to make sure once a corrective or preventive maintenance call comes for the mitigated tag, we address that on fast track basis to minimize risk exposure and apply any other applicable mitigation.