Correlation of Piping System Detonation Test Data and System Analyses

Abstract

This paper describes hydrogen and nitrous oxide detonation experiments that were performed using an approximately 200-ft long 2-inch schedule 40 piping system. The objective of these experiments was to develop an understanding of the loads and forces imposed by internal detonation on piping combinations representative of a typical industrial piping system. The apparatus contained numerous straight pipe lengths with 90° and 45° bends, 90° elbows, and a tee along with rigid foundation supports that were connected to the pipe using typical u-bolt fasteners. As a detonation wave propagates through a gas-filled piping system, the pipe begins to respond globally once a detonation encounters a change in flow direction, such as a bend, causing a pressure imbalance due to both the internal detonation pressure and change in momentum of the reaction products. The resultant force imparts both axial forces and moments on the pipe exciting both extensional and bending modes. The test data was used to validate two finite element (FE) models developed using the ANSYS finite-element program: a hybrid model that made use of both shell and beam elements, to determine the interaction between shell and beam modes, and an all beam element model. An additional beam element model was developed using the Bechtel National Inc. software ME101 that was also found to be in agreement with the measured and ANSYS calculated frequencies and support loads. In addition to the detonation testing, the finite-element models were validated against experimental modal analysis data of the piping system that identified the primary modal frequencies and vectors. These data were compared to the modes extracted from finite-element models of the piping system.