Federal investigators said this week that a Louisiana chemical plant exploded in 2013 due in large part to a "poor process safety culture" during the preceding dozen years.
The U.S. Chemical Safety Board's final report on the explosion of the Williams Olefins plant in Geismar found that a "reboiler" — a type of heat exchanger — was improperly protected against a buildup of pressure.
Two workers were killed and 167 others were injured when the reboiler ruptured and ignited a flammable vapor cloud on June 13, 2013. More than 62,000 pounds of toxic chemicals were reportedly released during the blast.
The Geismar facility produces ethylene and propylene for the petrochemical industry; at the time of the explosion, hundreds of contractors were working on an expansion to bolster ethylene production.
According to CSB analysts, the reboiler contained a liquid propane mixture that, when heated, sharply increased the pressure and caused the rupture. The reboiler was offline and isolated from its pressure relief device.
The investigation specifically found that Williams improperly managed the installation and oversight of block valves that could isolate the reboiler from the pressure relief system.
The Occupational Safety and Health Administration also cited the company for six workplace safety violations in 2014.
CSB acknowledged that Williams made some improvements following the incident, but recommended strengthening current safety management systems and conducting stronger safety assessments.
"The tragic accident at Williams was preventable and therefore unacceptable," CSB Chairwoman Vanessa Allen Sutherland said in a statement. "This report provides important safety lessons that we urge other companies to review and incorporate within their own facilities.”
The report, the agency said, also recommended that industry group the American Petroleum Institute update the industry standard for pressure-relieving and depressuring systems.