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June 01, 2023
CSB issues final report on fatal acetic acid release

The U.S. Chemical Safety and Hazard Investigation Board (CSB) released its final report on a fatal acetic acid release at the LyondellBasell La Porte Complex in La Porte, Texas, on July 27, 2021. The inadvertent removal of the pressure-retaining components of a valve caused the release of 164,000 pounds (lb) of an acetic acid mixture, killing 2 contract workers, according to the board.

Another contract worker and a company employee were seriously injured. The facility’s property damage, including loss of use from the incident, was estimated to be $40 million, according to the CSB.

“As this tragic incident shows, even a simple task can turn deadly if it is not performed properly,” CSB Chairperson Steve Owens said in a board statement.

“There have been similar incidents around the country involving plug valves being inadvertently taken apart when removing connected equipment. It is time to improve the design of these valves and take other protective actions, such as signage and training, before more workers are killed or injured.”

In the days leading up to the incident, an operations technician discovered a small leak in the methanol piping upstream from the unit’s acetic acid reactor. Upon discovery of the leak and shutdown of an adjacent unit, the shutdown of the acetic acid unit was also required.

LyondellBasell decided to use the shutdown as an opportunity to repair the leak and have contractors at the facility perform the work. To isolate the piping, company personnel chose to use the plug valve located between the leaking pipe and the nearby acetic acid reactor.

They developed a plan to remove the actuator, which was connected to the plug valve. A contractor’s work crew began removing bolts they believed were necessary to take off the actuator. However, the crew wasn’t aware the bolts they removed actually secured the pressure-retaining valve cover in place.

The plug ejected from the valve, releasing 164,000 lb of an extremely hot (238 degrees Fahrenheit) acetic acid mixture. The two contract employees were sprayed by hot acetic acid and inhaled its toxic fumes, resulting in their deaths. Two other workers were seriously injured, and 29 employees working in an adjacent unit were transported to medical facilities for further evaluation and treatment.

The CSB’s investigation identified two key safety issues:

  • Valve design to prevent human error: The CSB identified four similar incidents when pressure-retaining components of a plug valve were removed while attempting to remove equipment. The recurrence of these types of incidents points to the need for a further redesign of plug valves so it’s more difficult to remove pressure-retaining components while attempting to remove actuating equipment.
  • Providing workers with conditions, procedures, and training to safely conduct work: Both the company and the contractor considered the removal of the actuator a simple task and didn’t provide the work crew with any sort of procedure or training and didn’t adequately assess the potential risk of the operation before commencing work.

The CSB has plans to close its investigations into nine other incidents by the end of the year, including a final report on a nitrous oxide release at the Foundation Food Group in Gainesville, Georgia. The Occupational Safety and Health Administration’s investigation resulted in nearly $1 million in fines for 4 employers at the poultry processing facility.

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