Failure Analysis and Redesign of Supply Piping at Weld Joint

Abstract

The focus of this study is to investigate the dynamic fluid forcing that the nozzle and upstream piping might experience. Due to the presence of high LOF scores within operational flow rates indicates that Flow Induced Turbulence (FIT) is a possible cause of the vibration and weld cracking. CFD analysis to find fluid flow and force acting on pipe due to flow was provided. CFD analysis of the elbow located at the bend of the supply piping indicated turbulent flow around the bend, with a range of forcing frequency content up to 40 Hz. Hence, Finite Element Analysis (FEA) on the supply piping and spray pipe should be performed, using the fluid forces predicted by the CFD analysis. FEA results confirm the source of the Flow Induced Vibration, and to allow design modifications to be assessed. Based on ASME and other piping design standards we conclude adding extra support, as well as increasing weld size around the flange, are potential solutions to reduce the LOF score.