Preventing deadly explosions and fires
06 August 2010
The US Chemical Safety Board (CSB) has approved urgent safety recommendations to OSHA, NFPA and others. The draft recommendations, which were approved without amendments at a public meeting in Portland, CT, aim to prevent deadly explosions and fires during pipe cleaning and purging operations.
The recommendations - directed to the Occupational Safety and Health Administration (OSHA), the National Fire Protection Association (NFPA) and others, result from extensive CSB investigations into the February 7, 2010, explosion at the Kleen Energy power plant in Middletown that caused six deaths and multiple injuries, and the June 9, 2009, explosion at the ConAgra Foods Slim Jim plant in Garner, North Carolina, 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 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.
OSHA is also urged to require that companies involve their workers and contractors in developing safe procedures and training for handling fuel gas.
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.
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