The Chemical Safety Board (CSB) yesterday approved two “urgent” recommendations on gas purging safety and called on the National Fire Protection Association (NFPA), American Gas Association (AGA), and the International Code Council (ICC) to adopt them to strengthen national fuel gas code provisions.
The group, which investigates industrial chemical accidents, said its call to tighten up safety practices come as a direct result of its investigation into the blast at ConAgra’s Slim Jim plant in Garner, North Carolina, in June 2009. The explosion killed four people, critically injured three and hospitalised 67 in total.
Catastrophic explosion
CSB investigators discovered the “catastrophic explosion” resulted from the build up of significant amounts of natural gas that had been purged indoors from a new 120-foot length of pipe during the start-up of a new water heater in the plant that made the 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.
CSB Chairman John Bresland said: “The board is very concerned that companies across the country continue to purge pipes indoors. Currently, the codes of the NFPA and ICC do not require gases to be vented outdoors or define adequate ventilation or hazardous conditions, nor do they require the use of combustible-gas detectors during these operations.”
The CSB said its recommendation urged the NFPA and ICC to alter their codes. Both the NFPA and ICC are prominent bodies whose guidelines are used and followed by government bodies, private organizations and individuals nationwide, said the agency.
Donald Holmstrom, head of the CSB investigation, said his team made the proposal after discovering gaps in the fuel gas code.
“Purging flammable gases into building interiors is a recipe for disaster,” he said. “At ConAgra, we determined the accident would not have happened had the gas been vented safely outdoors through a hose or pipe.”
Since the June 2009 accident, ConAgra has changed its policy so that purging is done outside.
Recommendations
The new measures called for the NFPA and the American Gas Association (AGA), to enact tentative interim and then permanent changes to the National Fuel Gas Code – requiring all purged gases to be vented in “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 CSB has examined several other similar accidents in which gas was purged indoors and not detected,” said Holmstrom. “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.”