Pressure Relief MonitoringSource: Schneider Electric, Telemetry & Remote SCADA Solutions
Pressure relief valves are critical safety devices that act to protect equipment and personnel in the event of dangerous pressure build up in process piping and vessels. Normally closed, these devices are typically controlled by a spring force and have no auxiliary source of power. As the operating pressure approaches the opening point of the valve, the valve will simmer or weep much like a tea kettle before the whistle blows. When the sealing surfaces are in good condition, emission and product loss is limited to the release of excess pressure, however as time goes on, a percentage of these valves will leak into the atmosphere or waste collection systems that normally go to flare.
These valves are usually mounted on the top of vessels and are often at inaccessible locations that require special equipment and safety procedures for insite inspections. The typical inspection approach is to schedule the removal and shop inspection of pressure relief valves on a time interval that is established based on historical or design criteria. It is common to find a large percentage of the valves fail seat leak testing at their scheduled inspection. 30% to 50% of valves tested do not pass pre-installation criteria during these tests. 5% to 10% of them are leaking so severely that they have become major sources of lost product and possible emissions.