Sam:
When we get a question on a leaky Pressure Relief Valve (PRV), my immediate instinct is to try to help stop this type of hazardous incident – ASAP. With your handle, I don’t believe I’ll receive any criticism for assuming that you are a Chemical Engineer by training. As it is, it turns out you are not, and since I am one (with 46 yrs experience) I can easily start out talking well over your head and we wouldn’t understand each other from that point on. I appreciate your candor and ask you to bear with me if my statements or questions seem kind of “stupid”. Our intent is to help, not to confuse. But because the nature of the beast is one of a technical engineering product, it inevitably turns out to be very technical and as such, tough to understand without the necessary background.
Regardless whether you’re an engineer or not, your concern is of importance since you clearly indicate that there are emissions involved and they are not being directed to the intended flare system. In fact, these emissions may be potentially hazardous. You are wise in seeking help and a solution to these abnormal occurrences – even though they may be “occasional”.
First, let me clearly define the basic operation of a PRV:
1) These devices are intended as pure safety devices to relieve any sudden or gradual buildup of internal process pressure due to process upsets, accidents, human error, equipment failure, etc. Their operation is to relieve excess pressure and once pressure relief is effected, the PRV re-seats back to the closed position – without any subsequent leakage through the seat (or the body) of the PRV.
2) If leakage occurs, then the PRV is clearly defective or operating in a defective manner;
3) Once a PRV starts to leak, it must be removed and repaired before being used again;
The best way to get a clear understanding and gather basic knowledge about the methodology of how a PRV works and how it is designed (although you may not be interested in the engineering design portion) is to carefully read and study the API Recommended Practices I noted above. From what you describe as your work function at the plant you are working at, I would caution you to not tolerate being in the vicinity of a leaky PRV. The chemicals being relieved may be toxic or flammable – or both. Since you are an outside contractor doing work within the plant, you would be wise to educate yourself as much as possible regarding the basic equipment involved in your work – especially PRVs.
I really wish you could furnish us with concise and accurate technical details so that we could be of definite help to you. As it appears to me, you may be able to seek local help from plant engineers who should be aware of the leaky PRVs and be able to explain the nature of the fluids involved and the safety situation. If we can be of further or additional help, please follow up this thread with additional, detailed information that you may gather in the field.
Good luck and stay safe.
