Static Head Considerations for Relief Systems Design: Two Case Studies

The process of evaluating a facility’s relief system design can be time consuming and costly. Engineers are frequently tasked with finding the balance between accuracy and efficiency. While this may result in simplifying the analysis, this paper cautions the user against overlooking the impact of static head in pressure relief design. Failure to account for the increased pressure due to static head may result in designs where the overpressure exceeds the maximum allowed by the code of construction. This paper will look at two different cases where static head was not accounted for, and the mitigations that were used to solve the issues in the most cost-effective way. First, when dealing with the liquid head on an offshore platform, there are many different levels on the platform and protecting the different assets in the liquid handling train requires an evaluation of the potential pressure increase due to static head. Second, when evaluating a column system, it is important to ensure that the relief device provides protection for every equipment within the system. These two case studies illustrate the importance of accounting for static head in relief systems design, and describe potential mitigation options where the original design did not include static head.