Avoiding Pressure Relief Problems

Pressure relief valves and rupture disks are critical safety devices for protecting personnel and processing equipment from overpressurization situations. Presented here are several engineering practices that can help to identify and address common problems with the pressure relief systems of chemical process industries (CPI) facilities. Common causes of overpressurization Overpressure situations can have a variety of causes. Here are some common situations that may cause increased pressure in processing facilities. Each potential cause is followed by one or more factors that contribute to the overpressure. • External fire: Potential vapors from the fire must be relieved with a safety valve on the vessel • Blocked outlets: Blocked outlets can be caused by control valve failure, inadvertent valve operation and others • Utility failure: General or partial power failure, loss of instrument air, cooling water, steam, fuel gas or fuel oil • Loss of cooling duty: Loss of quench steam, air-cooled exchanger failure, loss of cold feed or loss of reflux • Thermal expansion: External heat can cause liquid volume to rise in fluids that are blocked in a vessel or pipeline • Abnormal heat input: Increased…