Modeling and Computation of Reaction Forces on Relief Piping during Depressurization

The sudden opening of a relief device, during an overpressure event, will cause the relief piping to experience dynamic loads. A pressure wave may be generated that travels at the speed of sound through the fluid. This has lead to force imbalances, particularly on long pipe segments, that can potentially damage the relief system, or prevent the relief system from operating properly. In order to design and properly protect the relief piping with the necessary supports, it is critical that a detailed analysis of the dynamic loads (e.g. thrust, momentum and wave), following the opening of a pressure relief device, is performed. In many cases, simple analytical techniques may not be appropriate, and a time history analysis of the loads acting on the relief system may be required. To address this phenomenon, an evaluation of the dynamic loads using RELAP5 (Reactor Excursion and Leak Analysis Program) software will be discussed. The RELAP5 software can be used to analyze fluid transients and compute resulting loads. It is possible to evaluate systems undergoing single phase or two phase relief.