Yesterday the Chemical Safety Board (CSB) announced the publication of a report on the 2023 explosion and ethylene oxide release incident at the DOW plant in Plaquemine, Louisiana. The incident resulted in the release of 31,000-lbs of EO, but no one was reported injured and there were no deaths. The CSB reported three safety issues identified and published four safety recommendations. This leaves seven open investigations.
The incident involved the vapor relief system. Leaks in the system allowed air to enter the piping. When debris from equipment left in a large reflux drum punctured a rupture disk attached to the system, EO vapors entered the piping and created a flammable atmosphere in the piping. The resulting explosion propagated through the pressure relief system.
Safety Issues
The report identifies three safety issues related to the incident:
Vessel closure practices – The incident began when work lights were inadvertently left behind in a reflux drum after the completion of turnaround maintenance and inspection activities,
Inerting system control – Despite the widespread industry knowledge about the importance of using nitrogen to prevent the reaction of ethylene oxide, Dow did not adequately monitor or maintain the inert atmosphere of the pressure relief piping between the rupture disc and the process relief valve to ensure that an inerting environment persisted, and
Pressure relief system design – The system could have been modified when the product cooler was replaced in 2010 to eliminate the threat of thermal expansion and eliminate the hazard of venting ethylene oxide into the reflux drum or another location.
CSB Recommendations
As a result of the investigation the CSB issued four recommendations, one for Dow Chemical, two for the National Fire Protection Agency (NFPA), and one for the American Society of Safety Professionals (ASSP). Dow had already taken appropriate actions on their vessel closure practices, so no CSB recommendations were made on related issues. The four reported recommendations are:
Dow Chemical - 2023-03-I-LA-1 – At all Dow ethylene oxide facilities, identify all process lines in ethylene oxide service that should be or are inerted and currently are not continuously monitored during normal operation. For all lines identified, determine whether the line can be eliminated, and if not, establish proper controls such as inerting and monitoring to ensure the process line is adequately inerted.
NFPA - 2023-03-I-LA-2 – Update NFPA 350 Guide for Safe Confined Space Entry and Work to provide guidance on how to ensure that vessels that have undergone confined space entry are left clean and ready for startup after the entries are completed.
NFPA - 2023-03-I-LA-3 – Update NFPA 326 Standard for the Safeguarding of Tanks and Containers for Entry, Cleaning, or Repair to provide requirements for to ensure that vessels that have undergone confined space entry are left clean and ready for startup after the entries are completed.
ASSP - 2023-03-I-LA-4 – Update ANSI/ASSP Z117.1 Safety Requirements for Entering Confined Spaces to provide guidance on how to ensure that vessels that have undergone confined space entry are left clean and ready for startup after the entries are completed.
With these four new recommendations the CSB’s total number of recommendations is now 1030, with122 of those recommendations still open.