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Dow Louisiana Operations Explosions

Overview

On July 14, 2023, at approximately 9:15 p.m., multiple explosions and fires occurred in the Dow Louisiana Operations Glycol II Ethylene Oxide Finishing unit in Plaquemine, Louisiana. The incident resulted in the release of approximately 31,525 pounds of ethylene oxide, substantial property damage, and a shelter-in-place order for nearby residents. No injuries were reported.

Incident Snapshot

Field Value
Facility / Company Dow Chemical Company
Location Plaquemine, LA
Incident Date 07/14/2023
Investigation Status The CSB's final investigation was released on February 26, 2026.
Accident Type Explosion and Fire
Final Report Release Date 02/26/2026

What Happened

  • On November 20, 2020, the rupture disc protecting the product cooler was replaced as part of regular maintenance and inspection activities.
  • After installation of the rupture disc, Dow workers pressurized the pressure relief piping between the rupture disc and PRV with 2.4 psig of nitrogen.
  • Over the next two months, the nitrogen pressure gradually decreased, eventually reaching atmospheric pressure and even showing negative gauge pressure for periods of time.
  • In May 2023, the Glycol II unit underwent a turnaround and the reflux drum was internally cleaned and inspected.
  • Portable work lights with magnetic bases were checked out during the turnaround, but five of these lights were never returned following the turnaround.
  • The reflux drum manway was closed on May 28, 2023.
  • After the turnaround work was complete, the ethylene oxide unit was started up and began operating without issues.
  • On July 14, 2023, at approximately 6:52 p.m., one of the reflux pumps shut down due to a high-high vibration interlock.
  • The operator found what looked like a scrap piece of insulation on the vibration probe wiring and restarted the pump successfully.
  • At approximately 9:17 p.m., an explosion occurred in the vicinity of the reflux drum.
  • After the explosion, two process operators immediately evacuated the area.
  • The lead process operator reported the fire to the site’s Emergency Services and Security department dispatcher at 9:18 p.m.
  • At 9:20 p.m., ES&S responders arrived at the scene to fight the fire and establish the Incident Command.
  • At 9:21 p.m., the Glycol II unit reported to ES&S that all of its personnel were accounted for.
  • At approximately the same time, control room operators executed the Glycol II unit’s automatic procedure to shut down the unit.

Facility and Process Context

  • The incident occurred in the Glycol II unit of Dow Chemical Company’s Louisiana Operations facility located in Plaquemine, Louisiana.
  • The LAO site’s industrial park had 23 production units manufacturing more than 50 different intermediate and specialty chemical products, including ethylene oxide.
  • The LAO site was covered by OSHA’s Process Safety Management standard and EPA’s Risk Management Program rule because it contains quantities of ethylene oxide exceeding the OSHA and EPA thresholds.

Consequences

  • No injuries were reported as a result of the incident.
  • Approximately 31,525 pounds of ethylene oxide were released during the incident.
  • Dow reported that its property damages were estimated to be $43 million.
  • A shelter-in-place order was issued for residents living within a half-mile of the Dow site and was lifted at approximately 3:40 a.m. on July 15, 2023.

Key Findings

Immediate Causes

  • The puncture of a rupture disc by metal debris that allowed the introduction of ethylene oxide into piping that contained air.
  • The ethylene oxide ignited, and the ethylene oxide and combustion products propagated through pressure relief piping to a reflux drum that was filled with ethylene oxide.
  • The ethylene oxide in the vapor space of the reflux drum heated and decomposed, causing the reflux drum to fail catastrophically due to increased pressure from the decomposition reaction.

Contributing Factors

  • Dow’s inadequate vessel closure procedures and practices, which allowed the vessel to be restarted without ensuring that it was adequately cleaned and the work lights removed.
  • Debris from the work lights moved downstream to the product cooler and penetrated the product cooler’s rupture disc.
  • Dow’s failure to maintain an inert atmosphere in the pressure relief piping and the lack of requirements to ensure that the piping segment remained inert during operation.
  • The design of Dow’s product cooler’s emergency pressure-relief system, which discharged its pressure-relief effluent back into the reflux drum.

Organizational and Systemic Factors

  • At the time of the incident, Dow had few procedures in place to ensure that debris was not left behind after confined space entries and work in vessels.
  • Dow’s vessel closure process had no official procedure in place related to tracking equipment placed inside a vessel during maintenance and inspection activities requiring confined space entries.
  • Dow’s vessel closure process and practices did not adequately identify whether the reflux drum was clean and empty after maintenance was completed.
  • 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.
  • Dow’s process hazards analysis overlooked the risk and potential consequences of pressure relief piping systems losing their inert atmosphere.
  • Dow did not adequately assess the risk of venting to a vessel full of reactive ethylene oxide and did not analyze safeguards needed to mitigate ignition within the pressure relief piping.

Failed Safeguards or Barrier Breakdowns

  • The work lights were not removed from the reflux drum before it was returned to service.
  • The Vessel/Nozzle Closure Form did not provide guidance on how operators are expected to check for debris or what steps to take to ensure a vessel is clean and free of debris.
  • The final closure process relied on a visual inspection without the aid of inspection tools or a confined space entry.
  • The pressure relief piping between the rupture disc and PRV did not have adequate inerting nitrogen.
  • There was no low-pressure alarm present on the pressure indicator.
  • Dow did not install oxygen monitors or other similar devices on the rupture disc discharge piping.
  • The product cooler pressure relief system vented to the reflux drum.

Recommendations

  1. 2023-03-I-LA-R1 | Recipient: The Dow Chemical Company | Status: Open – Awaiting Response or Evaluation/Approval of Response | Summary: 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 if the line can be eliminated, if not, establish proper controls such as inerting and monitoring to ensure the process line is adequately inerted.
  2. 2023-03-I-LA-R2 | Recipient: National Fire Protection Association (NFPA) | Status: Open – Awaiting Response or Evaluation/Approval of Response | Summary: 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.
  3. 2023-03-I-LA-R3 | Recipient: National Fire Protection Association (NFPA) | Status: Open – Awaiting Response or Evaluation/Approval of Response | Summary: 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.
  4. 2023-03-I-LA-R4 | Recipient: American Society of Safety Professionals | Status: Open – Awaiting Response or Evaluation/Approval of Response | Summary: 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 and are left clean and ready for startup after the entries are completed.

Key Engineering Lessons

  • Confined-space vessel closure must include a reliable method to verify that vessels are clean and free of debris before startup, not visual inspection alone.
  • Process lines in ethylene oxide service that are intended to be inerted should be continuously monitored or otherwise controlled so the inerting environment is maintained during normal operation.
  • Pressure relief systems should not create a path that can return reactive effluent to a vessel containing ethylene oxide without adequate safeguards against ignition and decomposition.
  • Loss of inerting in pressure relief piping can create a serious ignition hazard and should be explicitly addressed in process hazards analysis.

Source Notes

  • Priority 1 final report used as the authoritative source for causal findings, sequence, consequences, and recommendations.
  • Priority 3 recommendation status summaries were used only to confirm recommendation status and wording where consistent with the final report.
  • Where source documents used slightly different release quantities (over 31,000 pounds vs. approximately 31,525 pounds), the final report value was retained.
  • No injuries were reported in the final report; empty injury fields in lower-priority summaries were not used to override this finding.

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