U.S. Issues Safety Rules on North Carolina Plant Gas Explosion

February 5, 2010

On a 2-1 vote, the U.S. Chemical Safety Board yesterday recommended that national fuel gas codes be changed to improve safety when gas pipes are being purged of air during maintenance or installation of new piping. The federal recommendations came after a probe of the deadly explosion at a ConAgra Slim Jim snack factory in North Carolina last year.

The draft recommendations urge the National Fire Protection Association (NFPA), American Gas Association (AGA), and the International Code Council (ICC) to strengthen the national fuel gas code provisions on purging.

If adopted, the guidelines would require that purged gases shall be vented “to a safe location outdoors, away from personnel and ignition sources.” In cases where outdoor venting is not possible, companies would be required to seek a variance from local officials before purging gas indoors, including approval of a risk evaluation and hazard control plan. The recommendation would also require the use of combustible gas detectors to continuously monitor gas concentrations; the training of personnel about the problems of odor fade and odor fatigue; and warnings against the use of odor alone for detecting releases of fuel gases.

The June 9, 2009, natural gas explosion at the ConAgra Slim Jim production facility in Garner, North Carolina, caused four deaths, three critical life-threatening burn injuries, and other injuries that sent a total of 67 people to the hospital.

CSB investigators determined that the catastrophic explosion resulted from the accumulation of significant amounts of natural gas that had been purged indoors from a new 120-foot length of pipe during the startup of a new water heater in the plant that made Slim Jims, a popular beef-jerky product. During pipe purging, workers feed pressurized gas into a pipe in order to displace air or other gases so that only pure fuel gas remains in the piping when it is connected to an appliance such as a water heater or boiler.

The Associated Press reported in September that the board initially voted down a similar proposal from its staff. Two board members had argued that code writers should be the ones to decide on any new written rules, not the safety board.

In yesterday’s vote, board Chairman John Bresland and member William Wark voted to approve; board member William Wright voted to disapprove. There are currently two board vacancies.

Current national safety codes, developed by a committee convened by the National Fire Protection Association and the American Gas Association, say gas purges “shall not be discharged into confined spaces or areas where there are sources of ignition unless precautions are taken.”

North Carolina has since voted to enact emergency changes to its code, adopting the new safety suggestions.

A settlement last month between ConAgra and the state Labor Department over the Slim Jim plant accident said a contractor released a mixture of pressurized gas and air into an enclosed room while installing a natural gas-fired water heater.

ConAgra agreed to pay $106,000 for workplace safety violations.

CSB said it has examined several other similar accidents in which gas was purged indoors and not detected.

“We have determined that workers cannot rely on their sense of smell to warn them of danger, in part because people become desensitized to the odorant added to natural gas and propane. Gas detectors must be used,” CSB investigations supervisor Donald Holmstrom said.

Other incidents examined by the CSB include: a 1999 explosion at a Ford power plant in Dearborn, Michigan, killing six, injuring 38, and causing a $1 billion property loss; a 2008 explosion at a Hilton Hotel under construction in San Diego, California that injured fourteen people; a 2005 school explosion in Porterville, California, burning two plumbers; and an explosion at a hotel in Cheyenne, Wyoming, in 2007 severely burning two plumbers.

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