CSB: Outlaw Natural Gas Blows

Thursday, October 7, 2010 @ 08:10 AM gHale

Natural gas blows should not occur during power plant construction, said U.S. Chemical Safety Board (CSB) Member Mark Griffon who called on the American Society of Mechanical Engineers (ASME) to adopt the CSB recommendation.
The urgent recommendation was one of 18 issued this past June 2010 following the natural gas explosion that killed six workers and injured dozens of others at the Kleen Energy plant in Middletown, CT February 7, 2010. The plant was under construction at the time.
Workers used hundreds of thousands of cubic feet of natural gas to clean debris from gas pipes used to fuel electricity-producing turbines.The gas accumulated in and around the buildings, was ignited by an unknown ignition source, and exploded.
“The CSB believes that using natural gas or other flammable gases to clean fuel gas piping is inherently unsafe and should be prohibited,” Griffon said. He cited other accidents to show that explosions resulting from flammable gas blows have the potential of causing death, serious injuries, and costly property damage.
Griffon said the practice of using gas blows, or forcing large volumes of flammable gas through piping to clear out debris, was common in construction of electric generating facilities. The CSB investigation of Kleen Energy, says “From a fire and explosion perspective, releasing large volumes of natural gas in the vicinity of workers or ignition sources is inherently unsafe.”
ASME is considering the CSB recommendation to prohibit gas blows and use inherently safer methodologies to clean piping. “It has been argued that the gas blow at Kleen Energy was not conducted properly to ensure the dispersion of the released natural gas and to prevent the gas from encountering ignition sources,” Griffon said. “This point overlooks the simple fact that cleaning piping with flammable gases presents an inherent explosion hazard. Cleaning piping with flammable gases presents an explosion hazard that cannot be wholly eliminated.”
Even if every effort is made to eliminate ignition sources, such as welding, or electrical equipment not rated for a hazardous environment, Griffon said, the friction of the gas flowing through the piping can cause an accumulation of static electricity and cause ignition; in addition, sparks from impacts of metal debris striking surfaces when the gas exits the piping can also ignite the gas.
Griffon said the CSB found other alternatives to gas blows which are safer. These methods include blowing air or nitrogen through piping, or by “pigging,” in which a cleaning device propels through the pipe using air.

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