There has been a lot of discussion recently about the five year inspection interval for Pressure Relief valves. I believe that a lot of this discussion comes from this quote out of the National Emphasis Program for Refineries CPL 03-00-010:
“If an employer has predetermined they will replace an existing relief valve with a new valve instead of testing it, they must still inspect the existing relief valve to determine if its service condition dictates that the inspection interval for the new relief valve should be shortened.”
This raises the question: If you are relying on the manufacturer’s recommendation to replace the Pressure Relief valves “at least every five years,” how do you know that the valve is actually still working after five years in service?
To answer this question some facilities are sending out a statistically significant number of their relief valves to be tested at a professional shop. There’s nothing wrong with that – but as of this moment I can’t find a single citation for NOT doing this.
OSHA’s own guidance in the NEP states that the facility must “inspect” the valve and that is not difficult to do. What you are looking for is obvious signs of corrosion or fouling. Generally speaking, fouling isn’t a big issue in Ammonia refrigeration systems, but corrosion can be if the headers aren’t designed properly.
It seems a general consensus is forming about how to deal with the question and it is this:
- Require inspection of your relief valves when they are replaced in your written Mechanical Integrity procedure. This inspection should be done by a supervisor that is competent to subjectively analyze the valve condition.
- Require that a valve be objectively analyzed (sent to a shop) if the condition of the valve cannot be determined subjectively.
- Require that the replacement interval for the Pressure Relief valve is set based on this inspection. (it should not be less frequent than the five year interval suggested by the manufacturer unless you can support that interval with engineering studies)
I believe if you do the above you’ll no longer have to worry about answering this type of NEP question regarding Relief Valves.