DuPont Gas Leak Design Issues

Friday, February 6, 2015 @ 03:02 PM gHale

Four design issues ended up revealed in the investigation of the deadly gas leak that took the lives of four workers at DuPont’s chemical plant in LaPorte, TX, in November, investigators said.

The U.S. Chemical Safety Board (CSB) Thursday revealed their initial findings from their investigation into the deadly gas leak.

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Rafael Moure-Eraso, chairperson of the CSB, said although DuPont has made great efforts to improve safety at their facilities, the company has also had three deadly incidents in the last five years; the latest of which was the poisonous gas leak at their LaPorte plant last November.

“Not only DuPont, but the industry as a whole must do much better,” Moure-Eraso said, adding “it is clear that the current process safety regulatory system is in need of reform.”

The CSB noted in their initial field investigation of the LaPorte incident, which is only 50 percent complete, the team found four design issues that contributed to the accident:
1. The process included several interconnections between the methyl mercaptan supply line and a chemical vent system, which allowed a toxic leak into an unexpected location, where workers ended up exposed with fatal consequences.
2. The chemical vent system, intended to safely remove harmful vapor from process vessels, had a design shortcoming that allowed liquid to accumulate inside. This liquid regularly caused pressure buildups in the vent, and operators needed to manually drain the liquid to prevent safety issues from interconnected equipment, such as reactors.
3. The vent drain that operators had to use was open to the atmosphere, meaning workers ended up exposed to whatever chemicals drained from the vent system.
4. The building’s design was in such a way that even had ventilation fans been working on the day of the accident, it could not necessarily protect workers from chemical exposure. And the CSB found those vents were not, in fact, working at the time of the accident.

Moure-Eraso pointed out this incident is one of many similar incidents investigated by the CSB and it reinforces the need for “regulators and companies [to] place greater emphasis on making designs as safe and possible and updating them on a constant basis.”

“The first DuPont accident investigated by the CSB, in January 2010, at DuPont’s manufacturing plant in Belle, West Virginia, resulted in the death of one worker when a braided steel hose ruptured, releasing highly toxic phosgene gas. The CSB investigation found that DuPont had not used the safest materials of construction for the hose – had not replaced the hose on the required maintenance schedule – had not installed a properly ventilated and alarmed enclosure around the phosgene to prevent worker exposure – and finally, had not required workers to use respirators around the phosgene storage area.

“The second DuPont accident investigated by the CSB occurred later in 2010 when hot sparks produced by welding ignited flammable vapors inside a chemical storage tank that had not been effectively isolated from a hazardous process at DuPont’s facility in Buffalo, New York. The tank had not been effectively isolated from a hazardous process. DuPont had not used an adequate gas detection system to monitor the area for the hazardous vinyl fluoride gas, which exploded.

“And finally, the accident we are discussing today — at the DuPont, La Porte facility here in Texas — was the most severe. Four workers were killed during the release of what DuPont estimates were more than 23,000 pounds of methyl mercaptan, a highly toxic, flammable, and volatile liquid.”

Moure-Eraso made a plea for companies to boost their process safety initiatives.

“Complex process-related accidents with tragic results are taking place across the country at companies of all sizes. This problem includes major corporations such as DuPont, not just smaller companies that some refer to as outliers. It is clear that the current process safety regulatory system is in need of reform, and that companies themselves must do more.

“We have found common factors contributing to major accidents like the one at DuPont La Porte. These include a lack of safe process designs and risk reduction targets, weak or obsolete regulatory standards, inadequate regulatory resources and staffing, and overly permissive industry standards.

“And the latest accident at DuPont is one of many incidents investigated by the CSB where we believe it will become clear that the process design was not as safe as possible,” Moure-Eraso said.

CSB board member, Manny Ehrlich, also said the investigation is ongoing and they will now start doing some field testing of devices.

“Investigators have been inside the manufacturing building on numerous occasions evaluating the process equipment, building layout, and safety systems,” Ehrlich said. “These systems include building ventilation, toxic gas detection, availability of emergency breathing air, and exit routes for workers, to name a few.”

“At this point, the field phase of the investigation is approximately 50 percent complete,” he said. “In the coming weeks and months, testing of field equipment such as check valves, block valves, and interlock systems will take place as well as verification of critical instrumentation.”

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