Chapter 5 - Pressure Vessel Internal Assessment

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This chapter discusses the assessment of the mechanisms that cause failures of internal pressure vessels. The most common failure of the internals of pressure vessels is fatigue. The failure involved is more than just fatigue alone. In a large fluidized bed, pulsation of the internal fluids initiates strong and rapidly changing forces. For such services, the internals must be designed adequately for these conditions. In this failure, the large pulsation responses throughout the fluidized bed ripped out trays and other internals, and they were piled up at the bottom of the vessel. A fatigue crack initiated in a gusset plate attachment set up the fatigue crack that propagated and allowed the air distributor pipe to break completely. The fatigue crack in the gusset plate attachment resulted in large stress concentrations. With a highly cyclic service, the fatigue crack initiated and resulted in the eventual failure of the air distributor pipe. The use of abrupt geometric boundaries on surfaces is not a good practice in cyclic service because of stress intensification.