(58c) Evolution of Relief Sizing at an Operating Company

Codes, Standards, and Recognized and Generally Accepted Good Engineering Practices regarding the engineering design of pressure relief systems have undergone significant revision over time.  This paper traces the development of the approach to relief system design by an operating company as the codes, standards, and RAGAGEP have changed and as the awareness of the recommendations of these various guidelines have penetrated the consciousness of the organization.  The paper will trace the development of the approach from simple sizing of orifice areas based solely on the external fire case, to the adoption of additional cases to be considered in the relief sizing, the evaluation of inlet and outlet pressure drops for reclosing devices (both pressure relief valves and low pressure devices), the consideration of reactive relief systems and different approaches to reactive cases, the evaluation of atmospheric venting of relief systems from a consequence assessment standpoint, the elimination or mitigation of relief sizing contingencies based on system limitations or active protective systems, and appropriate protection of gas-filled vessels with depressuring systems.  In addition, the paper will address new topics under consideration including relief valve stability.