The probable cause of an explosion and fire was a failure of the brazed aluminum heat exchanger (BAHX) due to thermal fatigue, says the U.S. Chemical Safety Board. The CSB has released its final report of the June 27, 2016, investigation of the explosion and fire at the Enterprise Products Pascagoula Gas Plant in Pascagoula, Miss.
The incident occurred when a major loss of containment in a heat exchanger resulted in the release of methane, ethane, propane and several other hydrocarbons. The hydrocarbons ignited, initiating a series of fires and explosions. Ultimately, the incident led to the site being shut down for almost six months.
The CSB report describes how thermal fatigue is believed to have occurred between the aluminum parts of a brazed aluminum heat exchanger. As an exchanger is heated or cooled, the tightly connected parts expand or contract. If the parts change temperatures at sufficiently different rates, the expansion and contraction can be disproportionate. Over time, this process weakens the metal and ultimately causes cracks, which can lead to the escape of hydrocarbons.
At the Enterprise Gas Plant, process data for the exchangers show that the brazed aluminum heat exchangers were repeatedly subjected to temperature changes that exceeded industry-recommended practices. This increases stresses on the connections within the heat exchangers as the aluminum parts push against and pull apart from each other.
Click here for the full report.