Citing initial findings from a fatal explosion in July, a federal safety agency has issued a warning to companies with storage tanks.
Investigators from the U.S. Chemical Safety Board (CSB) sent water samples from an exploded tank at the Omega Protein facility in Moss Point, MS, to a lab for testing.
What the lab found: microbial activity in the samples and offgassing of flammable methane and hydrogen sulfide.
The Omega explosion occurred during hot work and resulted in the death of one contract worker and severe injuries to another contract worker.
The water inside of the tank had been thought to be nonhazardous. No combustible gas testing was done on the contents before the hot work started.
The CSB says it’s now investigated three fatal hot work incidents since 2008 involving biological or organic matter in storage tanks.
At the Packaging Corp. of America (PCA) facility in Tomahawk, WI, three workers were killed on July 29, 2008, as they were performing hot work on a catwalk above a tank of white water – a slurry of pump fiber waste and water. The CSB identified hydrogen-producing bacteria in the tank. The hydrogen ignited, ripping open the tank lid and sending the workers falling to their deaths.
On Feb. 16, 2009, a welding contractor was killed while conducting repairs on a tank at the ConAgra Foods facility in Boardman, OR. The tank held water and waste from potato washing. Material decaying in the tank generated a flammable gas that ignited.
The CSB says companies, contract firms and maintenance personnel should know that inside a storage tank, seemingly non-hazardous organic material can release gases that cause the vapor space to exceed the lower flammability limit. After that happens, a small spark or even heat from hot work can cause an explosion.
Following recommendations from the CSB in 2012, the DuPont Co. instituted a series of reforms for hot work safety practices at its facilities, including combustible gas monitoring when planning welding or other hot work on or near storage tanks. An explosion at a DuPont chemical site near Buffalo, NY, killed a worker.
Monitoring for combustible gases in tanks is also recommended by the National Fire Protection Association (NFPA).