(111b) Case Study: Tube Rupture Scenario Credibility

When designing pressure relieving systems for heat exchangers, the potential for internal tube failure needs to be considered. The tube rupture scenario needs to be assessed when the low-pressure side of an exchanger can be significantly overpressured in the event of a tube rupture. API 521 “Pressure-relieving and Depressuring Systems” provides guidance on this topic and treats this scenario somewhat differently than other credible overpressure scenarios by considering this a remote scenario, allowing an alternate design basis (hydrotest) to be used.

This paper will provide guidance on the allowable methods to mitigate the tube rupture overpressure scenario, with a focus on evaluating the credibility of the scenario through a Tube Rupture Credibility Assessment (TRCA). A TRCA consists of a rigorous analysis of the heat exchanger design to demonstrate that the tube rupture scenario is not credible, eliminating the need to make costly modifications to the relief valve installation to accommodate the resulting flow from a tube rupture. This paper will also provide a case study of an Owner-User’s application of the TRCA and the resulting cost-savings.