The ever-controversial “check valve” has now been defined as to when it should be formally included in the piping MI inspection process. As we have discussed many times, if we claim a check valve in our PHA and/or SOP as a “safeguard,” then by all means, this valve has been defacto identified as a “safety critical valve”. Here is the official definition and requirements for “critical check valves”…
Check valves in piping systems that have been identified as vital to process safety. Critical check valves are those that need to operate reliably in order to avoid the potential for hazardous events, or substantial consequences should reverse flow occur.
Critical check valves should be visually and internally inspected to ensure that they will stop flow reversals. An example of a critical check valve may be the check valve located on the outlet of a multistage, high-head hydroprocessing charge pump. Failure of such a check valve to operate correctly could result in overpressuring the piping during a flow reversal.
The normal visual inspection method should include the following:
- Checking to ensure that the flapper is free to move, as required, without excessive looseness from wear.
- The flapper stop should not have excessive wear.
- This will minimize the likelihood that the flapper will move past the top dead central position and remain in an open position when the check valve is mounted in a VERTICAL position.
- The flapper nut should be secured to the flapper bolt to avoid backing off in service.
Leak checks of critical check valves are normally not required.