TIP #4: Be ready for the aftermath of a malfunctioning PRV.Pressure reducing valves are subject to wear and will eventually fail. For that reason, it is vitally important that you evaluate every component downstream from the PRV and determine the consequences of exposing those components to elevated pressures. If a PRV does malfunction, chances are that it will fail OPEN and allow full line pressure to be transmitted downstream (refer to Figures ZA and ZB). If your system has a safety relief valve mounted on the downstream side of the PRV, it will open in the presence of high pressure and protect downstream components. Steam traps used in systems that are protected by a safety relief valve may be rated at or above the relief valve setting but not lower. (If your steam system does not have relief valves, you should consider adding them.) Steam traps used in systems that include PRVs but do not use safety relief valves should be rated to operate at supply line pressure. If a steam trap installed downstream from a PRV is not rated at supply line pressure, undesirable condensate backup may occur in the event of a PRV failure. For example, if the traps draining a heat exchanger have a maximum pressure rating of 150 psi and, due to PRV failure, steam from supply lines at 250 psi enters the downstream system, the traps will fail to function. (A trap will open at pressure up to maximum rating but not at pressures appreciably in excess of maximum rating.) If the traps fail to open, condensate will back up into the heat exchanger and cause a variety of problems. Contact Us today for detailed Steam Trap and PRV selection support.
Prepare for a Malfunctioning PRV – Steam System Troubleshooting Tip #4