Posted By Kevin Vinson Can anybody give me some advice...! Under normal operating conditions the tank in question, contains LPS and its pressure relief valves (PRV's) will cope with normal overpressure. A steam ejector feeds the tank via a pressure control valve (PCV). This PCV is controlled by a 'non fail safe' DCS and has high pressure trip. If there is a fault and the ejector goes into an over pressure condition together with the simultaneous failure of either the PCV, DCS, or pressure switch, mps will enter the tank. The tank's PRV's would not be able to cope with the subsequent overpressure condition in the tank. The pressure switch and PCV are checked periodically and failures have been found. Could anybody comment if this a suitable system. It is my belief that the PRV's need uprating but I need to justify this. Could you please point me in the direction of any ACOps, design standards or guidance etc Many Thanks Kevin

Posted By John Webster Quite simply, the starting point is to assume a worst case scenario. Your control valve is stuck open, all of your electrical and electronic safety devices have failed and the highest pressure steam possible in the system is now flowing into your vessel at the maximum flow which your pipework pressure drop calculations will allow. If your vessel is not designed for this, and there are no other mechanical relief valves or bursting disks in the system to avoid this, then your vessel relief valve and pipework may have to be sized for this condition. As Kevin rightly says, expert advice should be sought. John