Enhancing Risk Management Using An Equipment-Based Pressure Relief System Analysis

A classical risk management strategy is to control a hazard by providing layers of protection between the hazard and the surroundings. These layers of protection may include operator supervision, control systems, alarms, interlocks, physical protection devices, and emergency response systems. For pressure systems, physical protection devices, such as pressure relief devices, are classified as the last layer of protection against overpressure scenarios that may lead to loss of containment. The significance of each layer of protection, including pressure relief valves, is determined through the implementation of risk assessment. Overall, the success of a risk management system depends on the quality of the inputs to the assessment process, including the quality of information on pressure relief valves.

Pressure relief devices are frequently managed using a relief device data sheet system that documents the valves installed on the process. Generally, a relief device data sheet includes the primary overpressure scenario for the protected system as the basis for the pressure relief device design requirements. Relying solely on pressure relief device data sheets, however, does not address unprotected equipment in a unit or plant, as overpressure scenarios are directly associated with pieces of equipment and systems and exist even if no relief devices are present. In addition, relying solely on pressure relief device data sheets further threatens quality of a risk management plan because a data sheet generally identifies only a single overpressure scenario per device, and the design scenario for a single relief device may not necessarily be the same as the design scenario for a disposal system, such as a relief header. Therefore, a comprehensive pressure relief systems management program cannot be achieved effectively using a traditional pressure relief device data sheet approach, which in turn cannot effectively support a successful risk assessment, the key component in an optimized risk management program.

A comprehensive, equipment-based pressure relief system analysis approach is therefore presented to address the inadequacies of a strategy that relies solely on relief device data sheets, which will result in a best practice to analyze and document a pressure relief system. Through experience, this best practice has proven to generate reliable input to the overall risk assessment process. In addition, the equipment-based best approach will be demonstrated to be a systematic methodology focused on ensuring all equipment are protected, and to be the most efficient workflow for pressure relief system design and analysis.