CSB Approves Urgent Recommendations to Prevent Deadly Explosions During Pipe Cleaning and Purging Operations

On June 28, CSB approved series of 18 urgent recommendations aimed at preventing fires and explosions caused when fuel gas is used to clean or purge gas pipes of debris, air or other substances, typically during facility construction and maintenance.

The recommendations, which were directed to OSHA, the National Fire Protection Association (NFPA) and others, resulted from extensive CSB investigations into the Feb. 7 explosion at the Kleen Energy power plant in Middletown, Conn., that caused six deaths and multiple injuries, and the June 9, 2009, explosion at the ConAgra Foods Slim Jim plant in Garner, N.C., that killed four workers and injured 67.

The accident at Kleen Energy occurred during the planned cleaning of natural gas piping during the commissioning and startup phase of construction. Natural gas was forced through large piping that was to fuel the plant’s large electricity-generating gas turbines, in an operation called a “natural gas blow.” This gas was vented directly to the atmosphere from open pipe ends that were less than 20 feet off the ground and were located in congested areas adjacent to the power generation building.

CSB investigators obtained gas company records showing some two million standard cubic feet of natural gas were released to the atmosphere during gas blows on Feb. 7 – enough, the CSB calculated, to provide heating and cooking fuel to a typical American home every day for more than 25 years. The gas found an ignition source and exploded.

In CSB’s recommendations, OSHA is urged to pass regulations that would prohibit the use of natural gas for pipe cleaning, the cause of the explosion at Kleen Energy, and would prohibit the venting or purging of fuel gas indoors, the cause of the explosion at the ConAgra Slim Jim plant. Both explosions resulted from releases of natural gas during the installation and commissioning of new piping that led to gas-fired appliances.

OSHA also is urged to require companies to involve their workers and contractors in developing safe procedures and training for handling fuel gas.

In testimony at a June 28 field hearing before a subcommittee of the U.S House of Representatives Committee on Education and Labor, CSB Board Member John Bresland said there is a “significant gap” in the current gas safety standards for general industry and construction, “a gap that threatens the continued safety of workers at facilities that handle flammable natural gas.”

An urgent recommendation directed at the NFPA urges the code-development organization to enact a tentative interim amendment as well as permanent changes to the National Fuel Gas Code that addresses the safe conduct of fuel gas piping cleaning operations. Under the draft recommendation, NFPA would be asked to remove key exemptions in the code for natural gas power plants and for high-pressure gas piping and to require the use of inherently safer alternatives to natural gas blows. CSB investigators determined that compressed air is a feasible and economical alternative to using natural gas for pipe cleaning and is already used by many companies.

Other draft recommendations would seek related safety improvements from the State of Connecticut and other states, the leading gas turbine manufacturers, the American Society of Mechanical Engineers and the Electric Power Research Institute.

“We believe that the 18 urgent recommendations proposed today – together with the two urgent recommendations we issued on Feb. 4 – address all of the principal root causes of these two tragic accidents,” Bresland told the House committee. “If adopted by the recipients, I have no doubt that future accidents will be avoided and lives will be saved as a result.”

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