CSB Report Describes Issues That Led to 2023 Ethylene Oxide Release, Explosion
A final investigation report (PDF) released in late February by the Chemical Safety and Hazard Investigation Board identifies safety issues that contributed to a fire, explosion, and the release of more than 31,000 pounds of ethylene oxide (EtO) at a Dow Chemical Company plant in Plaquemine, Louisiana. Although no workers were harmed during the July 2023 incident, process equipment was significantly damaged, and local officials issued a shelter-in-place order affecting hundreds of residents within half a mile of the facility.
Dow’s Plaquemine facility produces EtO, a substance used as an agricultural fumigant, medical sterilizer, and intermediary for manufacturing other products, such as ethylene glycol and antifreeze. The CSB report explains that EtO’s high reactivity makes it useful for creating other chemicals but potentially hazardous to produce, store, and handle. It is also a known human carcinogen.
On the night of the incident, CSB found, EtO leaked into the facility’s pressure relief piping through a rupture disc damaged by metal debris. Investigators determined the debris came from portable work lights accidentally left in a large reflux drum during maintenance several months earlier, which degraded when the unit was restarted. Once inside the pressure piping, EtO mixed with air and then ignited. The flame travelled through the pressure relief system to another reflux drum containing liquid and vapor EtO, which exploded.
CSB investigators found that Dow did not have a process for ensuring that maintenance workers removed all equipment from reflux drums and that the vessels were empty, clean, and ready to be closed. “When dealing with a highly hazardous chemical like ethylene oxide, even a seemingly small mistake can have enormous consequences,” CSB Chairperson Steve Owens said in a news release.
Dow also had not maintained an inert atmosphere of nitrogen in the pressure piping. Although nitrogen had been pumped into the pipes in 2020, it slowly leaked out over time, allowing the pipes to fill with air.
A third safety issue contributing to the incident was that the pressure relief piping vented back into the reflux drum containing EtO liquid and vapor. This hazard could have been eliminated during design changes made in 2010 and 2011, CSB found.
To address these safety issues, CSB recommends that Dow identify all process lines at EtO facilities that should be or are inerted and not continuously monitored, determine whether these lines can be eliminated, and establish controls where necessary. CSB also urges the National Fire Protection Agency and the American Society of Safety Professionals to update their respective confined space entry standards to include guidance for ensuring that vessels entered by workers are clean and ready for startup after the completion of work activities.
More information, as well as a link to download a PDF of the final investigation report, may be found in CSB’s news release.