CSB Addresses Gas Venting Dangers

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The U.S. Chemical Safety Board offered an update on its investigation of the Kleen Energy Systems LLC natural-gas power plant in Middletown, Conn., which resulted in five fatalities and 12 injuries. The explosion was caused by a cleaning practice is known as a “gas blow.”

CSB Lead Investigator Don Holmstrom said that industry personnel have indicated that gas blows are a common practice during the commissioning of new or modified gas pipes at their facilities. ‘At the same time that gas blows were underway, there were potential ignition sources present in the surrounding area, including inside the power plant building. There were many construction-related activities underway inside the building,” Holmstrom explained. Determining the exact ignition source is not a major focus of the CSB investigation at this point. In most industrial worksites, ignition sources are abundant and efforts at accident prevention focus first and foremost on avoiding or controlling the release of flammable gas or vapor, Holmstrom said.

“Initial calculations by CSB investigators reveal that approximately 400,000 standard cubic feet of gas were released to the atmosphere near the building in the final ten minutes before the blast. This gas was released into a congested area next to the power block building. This congested area likely slowed the dispersion of the gas. The gas built up above the lower explosive limit of approximately 4 percent in air and was ignited by an undetermined ignition source,” Holmstrom said.

A major focus of the CSB investigation is to determine what regulations, codes and good practices apply to gas blows. CSB strongly cautions natural gas power plants and other industries against the venting of high-pressure natural gas in or near work sites. It is investigating possible alternatives to this practice, including the use of air, steam, nitrogen, or water or the use of combustion devices to safely destroy the gas. Combustion devices like flares can safely burn up flammable gas or vapor, preventing the possibility of an explosion.

For more information, view the full transcript of Holmstrom’s comments at
http://www.csb.gov/assets/news/document/CSB_statement_2_25_2010.pdf.

WP