Better safe than sorry

An air receiver - or pressure vessel - is an important part of a compressed air system used to store compressed air as well as providing capacity during periods of peak demand. If improperly designed, installed, used or maintained, they can also be extremely dangerous and can lead to catastrophic outcomes such as fatalities, serious injuries and damage to property. 

As a result, legal requirements for design standards for internal pressure equipment are in place for vessels of various sizes and pressure ratings. And for pressure vessels with higher hazard levels independent design verifications may need to be undertaken. 

The ongoing condition monitoring of the vessel to ensure its safe operation, lies with the owner or operator of the pressure vessel. In accordance with the Standard AS/NZS 3788, depending on the size, design pressure and hazard level, an air compressor pressure vessel should be inspected externally every 2 years and internally every 4 years by a competent person.

One key component of an air receiver that needs to be inspected and certified on a regular basis is the pressure relief valve. Small but mighty, the pressure relief valve on an air receiver is a safety feature that effectively stops an air receiver from exploding if the pressure inside the vessel was to exceed its maximum allowable working pressure. 

It achieves this thanks to its spring-loaded release mechanism. When the pressure inside the air receiver gets too high, the pressure pushes the pressure relief valve open allowing air to escape. Once the air receiver falls back below its maximum allowable working pressure, the pressure on the spring eases and the pressure relief valve will close. You can understand then, why maintaining the integrity of the pressure relief valve is absolutely essential for the on-going safe operation of the compressed air system.

Depending on the environment within which the compressed air system operates (for example if the compressed air system is located inside or outside), it is generally recommended that a pressure relief valve should be inspected and certified every 12 months. Here an accredited inspector uses specialised equipment to test the functionality and effectiveness of the pressure relief valve. 

In between that time - again depending on the compressed air systems operational environment - it is also generally recommended that the pressure relief valve should be manually checked for correct operation by a Competent Person. By manually lifting the valve (if possible) when the system is not pressurised, a Competent Person can check to make sure the spring is still intact and that there is not a build up of grime that could cause the valve opening to stick. Don’t forget though, that this is general advice only and you should always consult the OEMs operating instructions.

The pressure relief valve is just one area of an air receiver that needs regular attention to ensure the on-going safety of a compressed air system, but as you can see it is also a very important one. For further information and guidelines when it comes to air receiver testing and inspection click here or see the further resources section below. 

Important: please note that only qualified and authorised personnel should perform maintenance tasks who have read, are conversant with and adhere to the safety instructions and section of the service manual applicable to maintenance of the piece of compressed air equipment. 

Further resources
Worksafe New Zealand: Working safely with boilers and other pressure equipment
Compressed Air Association of Australasia: Air receiver inspection: frequently asked questions

Kaeser Compressors NZ offer a comprehensive pressure relief valve inspection and certification service. For more information or pricing phone 0800 447 820 or simply fill in the form below and we will get back to you.