Posted By David Neilson I am looking for information regarding the reliability of pressure relief valves for a steam duty. So far I have one reference from an IChemE guide, but I am struggling to find any evidence to either support or contradict it. Can anyone out there help me ?

Posted By George Wedgwood This topic is fairly specialised and was one with which I was intimately involved some years ago, leading up to a specific concern that the HSE had about valve set-point reliability. There will be quite a lot of HSE words on the subject and Alan Smith was one engineer involved on their behalf. Also involved was the Electricity Industry National Interest Group (NIG)-(David Left, who could direct you to the material and whom I know still leads that NIG) Basically, the requirement under PSSR (Pressure Systems Safety regulations 2000) is for the written scheme of examination to specify inspection and test periods for all parts of the pressure system, including safety and relief valves (as protective devices) and these should be clearly identified, their safe operating limits specified and periods for inspection and test written down and signed by the Competent Person (formal appointment by the employer for pressure systems - usually the engineering inspection company such as Royal & SunAlliance Engineering Limited). Incidentally you also talk to Alan Fitzpatric at RSA Engineering (0161 235 3000 or email at alan.fitz@uk.royalsun.com) and he will talk you through the problems and solutions - he is a friend so mention my name. Such valves are notorious for having their set-points vary in use so regular bench testing or in-situ testing like Trevi Testing by Furmanite can be useful for the larger valves. What you can't do is ignore them and if tasked by the HSE, you should be able to demonstrate that you have a management system for your pressure system and protective devices. You can get some detail on such a system through Croners Publications - Management of Industrial Safety if it is still available, as I wrote a Chapter on this some years ago and it is still valid. If you have any problems with that, contact me on george.wedgwood@pgen.com or call 07836 718908. However, do read the Guidance on the PSSR 2000 and I think you will find it helpful (ISBN 0-7176-1767-X, Price £7.50 from HSE Books). I hope this helps. Regards, George