Posted By Robert Randall Any heating engineers out there who can help me with a pressure problem? The Pressure Systems Safety Regs. 2000 gives the following as one of the instances where relevant fluid in a system qualifies it as a pressure system; "...a liquid which would have a vapour pressure greater than 0.5 bar above atmospheric pressure when in equilibrium with its vapour at either the actual temperature of the liquid or 17.5 degrees Celsius; or...." My problem is that I have a hot water heating syetem with vessels containg hot water. The capacity of the vessels are greater than 250 bar litres (the old definition of a pressure system) but I am not sure from the new definition whether they qualify and should therefore have a written scheme and thorough examinations.

Posted By Robert Randall Thanks for that Paul but that is exactly my problem. I don't know how to calculate the vapour pressure and the information is not on the pressure vessels themselves. I suspect however that it will be well above 0.5 bar but need to be sure before I recommend thorough examination and a Written Scheme.