Safety Relief Valve Failure: Autoclaves Boiler-pressure system.

43. (2005):

The purpose of the safety relief valve is to open automatically at a predetermined pressure to prevent equipment failure and for the protection of persons. They are fitted as a backup safety measure to hot water pressure systems.

In a recent incident, an autoclave’s boiler electrical contact failed, causing the temperature of the boiler to increase uncontrollably. The safety relief valve, which failed to open, was designed to release at an operating pressure of 630 kPa. The boiler was found to be operating off the scale of the gauge - indicating an operating pressure in excess of 900 kPa.

In addition, several pressure relief valves have failed their inspection due to seizure of the manual pressure release lever not being operable and therefore non-operative in an automatic capacity (as a safety device) to release pressure when required.

Boiler and pressure vessels are inspected annually, but should be maintained throughout the year as per the manufacturer’s recommendations, and all records of maintenance recorded in the vessel’s logbook or on MAXIMO.

The brass safety relief valves, the type that failed, require more frequent maintenance than the stainless steel insert variety. Both types/models of pressure relief valves require ongoing routine maintenance. However, the stainless steel valve as quoted in the manufacturer’s recommended service advice, indicates less frequent maintenance is required, and with increased resistance to corrosion, they are less prone to suffer from seizer. The lifespan of the stainless steel valve is also longer.

When a pressure relief valve needs replacing, it is advisable to consider the quality and maintenance issues.

Budget Unit management are reminded to ensure that they comply with all of the manufacturer’s recommendations in regard to the maintenance and operational use of safety relief valves on boilers and pressure vessels under their control.