On a 2-1 vote at a public meeting in Raleigh, N.C., the U.S. Chemical Safety Board approved urgent recommendations to improve gas purging safety.
The draft recommendations, which were approved as presented by the staff without amendment, urged the National Fire Protection Association (NFPA), American Gas Association (AGA), and the International Code Council (ICC) to strengthen the national fuel gas code provisions for purging during maintenance or installation of new piping.
The recommendations arose from the CSB's ongoing federal investigation into the June 9, 2009, natural gas explosion at the ConAgra Slim Jim production facility in Garner, N.C., which caused four deaths, three life-threatening burn injuries, and other injuries that sent a total of 67 people to the hospital.
In preliminary findings presented at the public meeting on February 4, 2010, 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' 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.
CSB investigations supervisor Donald Holmstrom said his team made the recommendations to the board during the course of the ConAgra investigation after discovering gaps in the fuel gas codes.
“Purging flammable gases into building interiors is a recipe for disaster. At ConAgra, we determined the accident would not have happened had the gas been vented safely outdoors through a hose or pipe.”
Holmstrom noted that since the June 2009 accident, ConAgra has instituted strict policies on purging, requiring it be done to safe outdoor locations.
The CSB recommendations urge the NFPA and the AGA to enact tentative interim and then permanent changes to the National Fuel Gas Code. These 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 recommendations 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.
- Warnings against the use of odor alone for detecting releases of fuel gases.