CSB Releases Final Report into 2016 Pascagoula Gas Plant Explosion

Source: Chemical Safety Board

The U.S. Chemical Safety Board has released its final report of the June 27, 2016, investigation of an explosion and fire at the Enterprise Products Pascagoula Gas Plant in Pascagoula, MS.

The CSB determined that the probable cause was a phenomenon known as thermal fatigue.  The CSB also issued recommendations to two trade associations and local emergency responders.  

The incident occurred late in the evening on June 27, 2016, 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, which ultimately shut down the site for almost six months. 

The Enterprise Plant receives raw natural gas via a pipeline from the Gulf of Mexico and separates the material into two products: natural gas liquids, which serve as a feedstock to the chemical industry, and a natural gas fuel stream, primarily composed of methane.

A key piece of equipment used in the process is a brazed aluminum heat exchanger (BAHX), which allows for the transfer of heat between two different process streams while keeping the streams separate.

The CSB investigation determined that the probable cause of the incident was a failure of the BAHX due to thermal fatigue.

At the Enterprise Gas Plant, process data for the exchangers show that the BAHXs 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. At Enterprise, over a 17-year period, four different BAHX heat exchangers were repaired nine times.  

The 2016 incident, as well as four other BAHX failure events at other facilities, illustrate that relying on a leak-before-failure assumption is not adequate. 

Operators of midstream gas plants need a more robust assessment and risk management plan that considers thermal fatigue to prevent the risk of sudden and catastrophic rupture of BAHX. 

The CSB is issuing recommendations to two trade associations, the American Petroleum Institute (API) and GPA Midstream Association, to share information related to failure hazards of BAHXs from thermal fatigue.