An interactive 3D model of the heat exchanger used at the Enterprise Products Pascagoula Gas Plant in Pascagoula, MS is on display to understand how this type of heat exchanger operates and its vulnerability to thermal fatigue.
The probable cause of the incident was a failure of the brazed aluminum heat exchanger (BAHX) due to thermal fatigue, said investigators at the Chemical Safety Board (CSB) in a report. Their report details how thermal fatigue occurs between aluminum parts of a BAHX, which allows for the transfer of heat between two different process streams while keeping the streams separate.
As the exchanger heats or cools, 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.
In most cases, when a leak is found, it can end up repaired with minimal expense or consequence before a major loss of containment occurs, CSB investigators said.
Assuming that leaks will be discovered and can be repaired prior to a catastrophic failure is “leak-before failure.”
Thermal fatigue is a known factor to BAHXs and there is industry guidance on recommended limits for maximum cyclic temperature fluctuations during operation and rates of cooling or heating during startup and shutdown.
Click here to view the heat exchanger 3D model.