The preliminary investigation on the fatal explosion of a Geismar plant on June 13 pointed to a rupture in an offline reboiler on standby mode, officials said Thursday.
According to Williams Olefins LLC, which conducted an internal investigation, the reboiler was located in the propylene fractionator area of the plant, adjacent to the in-service boiler. A reboiler is a specific type of heat exchanger.
The heat input system of the in-service reboiler was undergoing regular evaluation and analysis work during the blast.
Officials said three main factors in combination with one another contributed to the explosion, which included the unexpected presence of liquid hydrocarbons in the reboiler in standby mode, the introduction of heat into the standby reboiler, and the pressure relief system was isolated from the reboiler that was in standby mode.
Investigators said the explosion of the standby reboiler created a vapor cloud that was ignited by an unknown source within seconds, causing the fire.
Officials said the preliminary findings may be revised depending on the results of ongoing metallurgical evaluation and testing.
The company said it continues to cooperate in a full and transparent manner with Occupational Safety and Health Administration and the U.S. Chemical Safety Board, as they conduct their respective investigations into the cause of the incident.