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Industrial Safety

US Chemical Safety Board issues delayed accident reports

CSB also identifies hundreds of serious incidents in past 2.5 years

by Jeff Johnson, special to C&EN
January 4, 2023

Remains of a chemical plant and a fire still burning in part of it.
Credit: US Chemical Safety and Hazard Investigation Board
Fire burned at TPC Group chemical plant in Port Neches, Texas, for more than a month in 2019.

Last month was busy for the US Chemical Safety and Hazard Investigation Board (CSB).

In December, the board concluded three long-stalled accident investigation reports and updated information on an ongoing investigation. The board also released a study concluding that over the past 2.5 years 224 incidents occurred in the US that were serious enough to trigger a CSB investigation. The incidents killed 31 people and caused 126 serious injuries. Of the 224 incidents, 101 resulted in more than $1 million in damages.

Also in December, the US Senate confirmed a new CSB member, Catherine J.K. Sandoval, and elevated CSB member Stephen Owens to chair the safety board. The CSB now has 3 members, short of its legally set level of five members.

The 25-year-old board’s charge is to investigate and determine the root cause of significant chemical accidents; recommend improvements to operations of refineries, chemical plants, laboratories, and other facilities; and boost federal and state regulatory oversight of these sites.

An accumulation of unfinished investigations has plagued the board for years. However, the board finalized several investigatory reports in 2022, cutting its backlog from a record high of 19 to the 13 pending now. The CSB also announced a schedule to conclude 11 more investigations by the end of 2023.

The American Chemistry Council (ACC), a chemical industry trade association, and former CSB member Rick Engler applauded the board for the confirmation of Owens and Sandoval and the uptick in report completions.

“ACC and its members are long-time supporters of the CSB,” Kimberly Wise White, ACC’s vice president of regulatory and scientific affairs, says in a statement. “We are committed to working with Chairman Owens and his fellow board members to apply valuable safety lessons with the common goal of preventing and mitigating future incidents.”

Engler says that while “the agency is clearly moving forward, CSB still faces difficult challenges, such as hiring staff with capability to address the underlying root causes of chemical incidents.”

The three investigations completed in December address a 2018 incident at the Husky Energy refinery in Superior, Wisconsin; a 2018 fire at the Kuraray America ethylene vinyl alcohol plant in Pasadena, Texas; and a 2019 explosion and fire that destroyed a TPC Group chemical facility in Port Neches, Texas.

The Husky explosion injured 36 workers, caused $550 million in damages, and released 17,690 kg of flammable hydrocarbon vapor. More than 2,500 residents were evacuated and a community shelter-in-place order was issued based on the potential risk of release of highly toxic hydrofluoric acid from the refinery.

The incident occurred during routine maintenance of a fluid catalytic cracking unit. Two pressure vessels exploded, propelling metal fragments up to 360 m away. They punctured a nearby asphalt storage tank, spilling some 17,000 barrels of hot asphalt that ignited, the CSB concluded.

The report makes a host of recommendations on improving process safety for this and similar refineries and for federal regulators at the Environmental Protection Agency and the Occupational Safety and Health Administration.

At the Kuraray facility, 23 workers were injured during the startup of a high-pressure reactor system following a scheduled shutdown for maintenance. High pressure conditions developed inside the reactor and activated its emergency pressure relief system, the CSB found. This discharged flammable ethylene vapor through piping into an area where contractors were working.

Over 1,000 L of ethylene were released in 3 min. The likely source of ignition was welding that was underway nearby, the report says. The workers suffered burns and injuries as they leaped from the second and third stories of structures to avoid the fire.

Among its recommendations, CSB urges design changes to separate workers from discharge piping and correction of several process safety management failures.

At TPC’s Port Neches facility, a piping section ruptured, releasing highly flammable butadiene that quickly ignited. The resulting pressure wave destroyed parts of the facility and injured two employees and a security contractor. The blast damaged nearby homes and buildings and was reportedly felt up to 48 km away.

Lumps of butadiene polymer in a form called popcorn had accumulated in a deadleg—a section of capped, unused piping. The polymer expanded, ruptured piping, and exploded. Leaking fluid fueled fires at the site for more than a month.

The incident resulted in $600 million in damages and mandatory evacuations.

The board recommended the company make several operational changes, including developing a system to discover and eliminate deadlegs, particularly in high-purity butadiene systems. It also urged the ACC to modify its industry guidance documents to incorporate these recommendations.

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