Stress rupture predictions of pressure vessels exposed to fully engulfing and local impingement accidental fire heat loads

Experiments have shown that pressure vessels made of ASME SA 455 steel can fail by high-temperature stress rupture in less than 100 min when exposed to accidental fire heat loads. The objective of this work is to develop a three dimensional finite element analysis (FEA) model capable of predicting structural failure in pressure vessels to assess the effects that various parameters have on vessel failure. These parameters included wall thickness, vessel dimensions, wall temperature and vessel internal pressure. Also, the effect of local hot spots on failure time was investigated. The finite element analyses were conducted on 500, 1000 and 33,000 US gallon pressure vessels using ABAQUS.From the results of the three dimensional finite element analyses it was found that shorter and/or thicker walled (with respect to vessel diameter) pressure vessels have greater fire survivability then longer and/or thinner walled pressure vessels. It was also found that if peak wall temperature and internal pressure were the same, pressure vessels exposed to fully engulfing fires would fail sooner than pressure vessels exposed to a local fire impingement. Also, it was shown that the MPC Omega method could be used to predict fast stress ruptures.