Pressure relief devices and systems are installed on a variety of equipment present at production and processing facilities.
Under the umbrella of “process” equipment (which includes oilfield production processes), the types of equipment that typically are protected by pressure relief systems include vessels, heat exchangers, pumps, compressors, piping, etc. In this context, “vessel” is used in the general sense of “pressure vessels.” Accordingly, examples of “vessels” include separators, scrubbers, columns (distillation, contacting, adsorption), reactors, accumulators, and filters, as well as other types. Heat exchangers of all types are included here: shell and tube, air-cooled, plate and frame, and fired heaters. Positive-displacement pumps and compressors nearly always are equipped with some type of pressure relief system; centrifugal pumps and compressors sometimes require the installation of relief devices. Piping elements are rated for some design pressure; relief devices are therefore often installed on piping to prevent that pressure from being exceeded.
Nearly all process industry facilities have on-site utility systems of some sort. Many of these utility systems are protected against causes of overpressure by pressure relief devices and systems. Some of the typical utility systems are listed below.
1. Steam Systems
Pressure relief devices are typically present throughout utility steam systems. These locations include the boiler itself, feed water drums, steam drums, and let-down stations.
2. Steam Turbines
Steam turbines used to drive pumps, compressors, and other rotating equipment are very often fitted with pressure relief devices to protect the turbine casing and downstream components against possible overpressure.
3. Cooling and Heating Systems
Heat transfer fluid systems – both heating and cooling -typically require pressure relief devices to protect against potential overpressure caused by leaks of process fluids into the (typically low pressure) heating or cooling system, or by abnormal operation of heat transfer equipment.
4. Lubrication Systems
Lubrication systems are often equipped with relief devices, typically on surge tanks and pumps.
5. Compressed Air Systems
Relief devices are usually installed on these systems, which include both instrument air and plant air systems. The equipment protected typically includes compressors, wet air receivers, dryers, and any equipment downstream of pressure let-down stations.
6. Fire Water Systems
Fire water systems often contain pressure relief systems installed on pump discharges.
7. Refrigeration Systems
In these systems, relief devices typically are required on compressor suction scrubbers, compressor discharges, liquid refrigerant surge vessels, economizers, and process heat transfer equipment (refrigerant evaporators).