A recommendation to the NFPA and NGA would require fuel gases to be vented outdoors away from personnel and any ignition sources, combustible gas detectors to be used in the area where the gas is released and employees would be trained on the problems of odor fade and odor fatigue. The recommendation would also allow for an exception to gas lines being purged outdoors with the approval of a risk evaluation and hazard control plan. The evaluation and plan would require that all non-essential personnel be evacuated from the area where the line is purged to keep the gas concentration much lower than explosive limit, ample ventilation be provided and ignition sources be controlled or removed from the area.
The second recommendation to the ICC would ask that the revised provisions to the National Fuel Gas Code be included in the International Fuel Gas Code.
The recommendations come because the issue of purging within buildings is a common practice to many in the workforce, CSB Chairman John Bresland said, and accidents like ConAgra’s have been documented for several years.
During the investigation, the five-member team found similar instances at a Hilton in San Diego as well as a 1999 explosion in Michigan that killed six people.
This was the first explosion of this sort the CSB has investigated.
The recommendations will be voted on long before a final report is expected, CSB Investigations Supervisor Donald Holmstrom said. If passed, they will come in time for the NFPA and NGA to evaluate the current codes.
Purging gas lines within a building can cause an explosion if not monitored and ignition sources are not controlled or removed from the area.
“This is what happened at ConAgra and this is what the CSB doesn’t want to happen again,” Bresland said. “Unfortunately, it took the tragedy in Garner to get us where we are now.”
Problems at ConAgra
When the contractor installed a new water heater at ConAgra last June, there was also 120 feet of natural gas piping installed for the unit. The contractor had difficulty lighting the water heater, indicating that the line needed to be purged of air and filled with natural gas.
Bresland said the purging took place intermittently for two and a half hours in the vac pump room where the water heater was located.
After the accident, ConAgra changed its policy on the purging of natural gas lines in the company’s facilities.
The June 9 explosion created serious structural damage to the building, caused by the collapse of double-T concrete ceiling panels, each weighing at least 11 tons. While the construction of the building is not in question, the officials said they are looking into the placement of the vac pump room.
An ammonia leak from a refrigeration system hindered rescue teams from entering the building immediately.
The explosion took the lives of four people and sent 67 others to the hospital, three of which involved life-threatening burns and one amputation.
The CSB will meet with experts and the public tonight at 6 p.m. at the Sheraton Raleigh in the Oak Forest Room. There will be parking available across the street from the building for the public.
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