Posted By Graham Carson Hi all Is water pumped into a pressure vessel held at 4 bar to feed an irrigation system classed as a relevant fluid as defined by these regs? I'm trying to work out if there shoud by a WSE in place for this pressure system. As always thanks in anticipation. Graham M Carson

Posted By Paul Leadbetter Graham According to the Regulations, a relevant fluid is: (a) steam; (b) any fluid or mixture of fluids which is at a pressure greater than 0.5 bar above atmospheric pressure, and which fluid or mixture of fluids is- (i) a gas, or (ii) 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 (c) a gas dissolved under pressure in a solvent contained in a porous substance at ambient temperature and which could be released from the solvent without the application of heat. Although the water in your application is at 4 bar, the applicability of the Regulations depends on whether the vapour pressure of water is greater that 0.5 bar above atmospheric at the temperature in question. I think this is unlikely (assuming the water to be at ambient temperature) although it is a long time since I was familiar with the vapour pressure vs temperature curve for water! Perhaps a physicist (or someone with a copy of the 'Rubber Handbook') can help you out on that point. REGARDS Paul Leadbetter