CSB Approves Urgent Recommendations to Prevent Explosions During Pipe Cleaning, Purging Operations
The recommendations - directed to the Occupational Safety and Health Administration (OSHA), the National Fire Protection Association (NFPA) and others - result from CSB investigations into the February 7, 2010, 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' 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 February 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 the CSB proposed 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.
The recommendations also urge OSHA to require that companies involve their workers and contractors in developing safe procedures and training for handling fuel 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. NFPA is 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 recommendations 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.
The CSB public meeting was held in Portland, Conn., on June 28. Following a public comment period, the board approved the recommendations without modifications in a 4-1 vote.