The Chemical Safety Board is commending the National Fire Protection Association for an emergency change it has made on indoor purging of gas pipes to the National Fuel Gas Code, addressing the cause of the fatal June 2009 blast at the ConAgra Slim Jim Plant in North Carolina.

That tragic and preventable accident cost four lives, injured 67 others, and led to a decision to close the plant, with the loss of hundreds of jobs in the region. The accident occurred during an operation to purge (or clear air) from a new steel gas-supply pipe that was connected to a newly installed industrial water heater.

The pipe was connected at the other end to the building’s natural gas distribution system. During the purging operation, gas was allowed to flow through the pipe and exit through an open valve inside the utility room where the water heater was located. Due to difficulties in lighting the water heater, the purging operation was continued for an unusually long time, eventually causing gas to accumulate above the lower explosive limit inside the building. The gas contacted an ignition source and exploded, causing extensive sections of the large facility to collapse.

The CSB noted that the accident at ConAgra was but one of a number of similar explosions caused by an intentional, planned work activity that inadvertently led to a large and unsafe release of natural gas into a workplace.

At the time of the accident, indoor purging of natural gas systems was not prohibited under the National Fuel Gas Code, a key consensus code of the National Fire Protection Association (NFPA) that has been adopted by many states and localities across the country. At the February 4 public meeting, the Board voted to make urgent recommendations to NFPA and the International Code Council to prohibit indoor purging and require companies and installers to purge flammable fuel gases to safe locations outdoors, away from workers and ignition sources.

“I am pleased that the NFPA made our recommendation a high priority and took immediate steps to improve the National Fuel Gas Code,” said CSB member John Bresland. “On August 5, the NFPA Standards Council gave final approval to an emergency code change, known as a Tentative Interim Amendment that will prohibit indoor purging of industrial gas lines operating at greater than 2 pounds per square inch gauge (psig) or meeting certain pipe size criteria.

According to the NFPA, the new requirements are designed to require outdoor purging for industrial, large commercial and large multifamily buildings.”

These new provisions would have required the gas pipe at ConAgra to be purged outdoors, away from personnel and ignition sources. Under the new requirements, purging must be monitored using appropriate detection equipment to prevent a significant release of flammable gas. The new requirements are similar to new safety procedures developed and implemented by both ConAgra and the State of North Carolina in the months following the tragedy.

“Outdoor purging is inherently safer than venting gas into a building. Had the gas pipe at ConAgra been safely purged outdoors, the explosion and resulting deaths and injuries could have been avoided,” said Bresland, who presided at a Chemical Safety Board public meeting in Raleigh, N.C. in February to present the CSB’s findings on the explosion at the manufacturing plant in the nearby community of Garner.

He encouraged all companies to study the new code recommendations and to purge flammable gases outdoors whenever possible. “I urge the NFPA to ensure that a prohibition on indoor purging and other safeguards are permanently incorporated into the National Fuel Gas Code, and I thank the NFPA leadership and members for their positive actions to promote worker safety.”

Prohibition by OSHA Urged

CSB also is urging OSHA to prohibit flammable gas blows during pipe cleaning operations, saying it believes that OSHA does have adequate authority to take this action and to start the standard setting process at any time.

The CSB found that the practice of gas blows is inherently unsafe. In its investigation of the Kleen Energy accident, the CSB found that several safe alternatives to pipe cleaning are available to the industry are already in use, such as compressed air, nitrogen and the use of a solid cleaning device propelled by compressed air that is referred to as a pig.

Furthermore, the CSB found companies have already begun to ban the practice. And at least one leading manufacturer of natural gas electric turbines, General Electric, has informed its customers it will not support the practice of gas blows to clear out pipes leading to the turbines.

A GE official discussed this during the CSB public meeting held in June in Connecticut. “The practice of using flammable gas to clean out pipes is inherently unsafe and I believe this practice should be prohibited by regulation, as the CSB board voted at its June meeting. I urge OSHA to examine our recommendation closely and work toward its adoption.”

The Chemical Safety Board voted to issue 18 urgent recommendations to various recipients, including OSHA, aimed at halting the dangerous practice of releasing large quantities of flammable gas in the presence of workers and ignition sources during cleaning operations.

Six workers were killed and there were numerous injuries on February 7, 2010, at the Kleen Energy power plant under construction in Middletown, Connecticut. A recommendation to OSHA called for, among other things, the promulgation of regulations to prohibit the release of flammable gas to the atmosphere for the purpose of cleaning fuel gas piping.

Last month, OSHA announced citations, proposed fines against construction companies and contractors at the Kleen Energy power plant construction site, and announced a plan to notify natural gas power plant operators of the dangers of natural gas blows.

“I was pleased that during his news conference, Dr. David Michaels, assistant secretary of labor for OSHA, stated his agency is studying the CSB recommendation to prohibit flammable gas releases during cleaning operations, and that OSHA agrees with the CSB that this problem must be addressed immediately,” said CSB Chairperson Dr. Rafael Moure-Eraso.

Dr. Michaels had previously said that OSHA likely does not have the authority to prohibit the use of flammable gases during pipe cleaning operations, and that promulgating such a regulation would take years. FSM