(64i) An Approach to Reducing Risk during Online Isolation, Removal and Maintenance of Relief Devices Using Engineering Assessment

Overpressure protection must be provided for pressurized equipment by means of pressure relief devices, which sometimes require isolation and removal for inspection or repair.  It would be advantageous to have a means of isolation without shutting down the process, especially in light of the additional risks associated with shutdown and startup; however, doing so may put the pressurized system at risk of being unprotected in the event of overpressure.  Current recognized practices of providing dedicated personnel for monitoring and responding to an overpressure event, or installation of an independent spare, are non-ideal in many instances.  An engineering assessment can identify specific ways for providing temporary overpressure protection, including elimination of root causes of overpressure events, provision of alternative pathways to overpressure protection, modification of process operations, and/or establishment of a means of equivalent or better risk reduction for the duration of the isolation.  Guidelines and examples are provided to illustrate the analysis, along with recommendations for documentation.