In response to recommendations by the U.S. Chemical Safety Board, E.I. DuPont de Nemours and Co. improved its hot work safety procedures globally.
The recommendations were issued as a result of the CSB’s investigation of a fatal hot work accident that occurred at DuPont’s Yerkes chemical facility in Buffalo, N.Y., on November 9, 2010, that killed a contract worker and injuring another.
DuPont’s new procedures require that hot work be avoided when possible ― an inherently safer approach ― and order that hot work be immediately discontinued if flammable gases reach a level of 10 percent of the lower explosive limit (LEL), as determined by gas-monitoring equipment.
“We see far too many preventable accidents involving hot work in flammable atmospheres around tanks,” Dr. Moure-Eraso said. “DuPont’s new procedures are a sound model for other companies, large and small, to emulate and should inform future regulatory developments in this area.” Most recently, in 2012 the CSB sent an investigative team to the Long Brothers oil well site in Arkansas, where three workers were fatally burned in a hot work accident while dismantling an oil tank. No combustible gas monitoring was conducted, CSB investigators found.
In its report on the Buffalo accident, the CSB found a number of deficiencies in the facility’s hot work permitting process and procedures that contributed to the accident. Contracted workers were welding atop a 10,000 gallon polymer slurry tank in a process area when hot sparks ignited flammable vinyl fluoride vapor that had accumulated inside the tank, triggering an explosion. The DuPont employee who signed the contractor’s hot work permit had no knowledge of the process to which the tank was connected or its associated hazards. Though the tank to be welded on was “locked out” from the process, an overflow line between adjacent tanks remained connected, allowing flammable vapor to accumulate inside the vessel where the welding was taking place.
In addition, the CSB found that despite National Fire Protection Association standards and industry good practices that call for testing the atmosphere inside tanks prior to conducting hot work, no internal tank monitoring was conducted.
The board’s recommendations urged DuPont to establish corporate policies and procedures requiring all facilities to audit their hot work permitting systems; isolate of process piping and similar connections prior to authorizing hot work; test for flammable gases inside containers prior to hot work; and require flammable gas monitoring during hot work in accordance with industry standards published by NFPA.
DuPont’s new standard, which it designated as S31F, requires that hot work permits be initiated and approved by individuals familiar with the scope of the work and associated hazards, and that both a job safety analysis and field audit be conducted prior to commencing work. The standard also requires isolating and removing energy sources from equipment where work is to be performed and sets up criteria for requiring either continuous or periodic flammable gas monitoring in the vapor spaces of process equipment and nearby containers during hot work operations.
DuPont's new procedure was accompanied by a comprehensive rollout package that was distributed to all U.S. locations. DuPont conducted series of technical training sessions for its employees and will provide periodic refresher training on a permanent basis.
As a result of the changes at DuPont, the CSB voted unanimously to change the status of all four recommendations to “Closed – Acceptable Action.”