In order to permit their removal and replacement without plant shutdown, pressure relieving devices may need to be isolated from the equipment they protect. However, the installation of isolating valves around protective devices is potentially hazardous as it introduces the risk of a system being left unprotected against over-pressure due to the relief path being inadvertently closed off. Existing standards offer little or no detailed guidance in this area.

EEMUA 184 plugs the gap by expanding on the guidance given in API RP 520 Part II and incorporating EEMUA Information Sheet 50 - The Importance of isolation management around relief systems. It outlines the case for using relief valves as a layer of protection, gives advice on managing safe isolation and stresses the importance of safe de-isolation after completion of relief system work. EEMUA 184 provides several examples in loss prevention history where the failure to adequately manage relief system isolations has been a major factor in causing process safety incidents.

It is essential to conform to local statutory legislation or regulations in relation to the use, and isolation of, relief devices. In some countries, conformance to certain standards and codes may be a mandatory requirement and specific standards, such as those pertaining to boilers, may specifically prohibit the installation of isolation devices.

Please note EEMUA Associates receive a 50% discount off the non-member price.