A fire and series of explosions at the Barton Solvents chemical distribution facility in Des Moines, IA, were caused by a static electrical spark resulting from inadequate electrical bonding and grounding during the filling of a portable steel tank, the U.S. Chemical Safety Board (CSB) determined in a final report.
The accident occurred in the packaging area of the facility as an operator was filling a 300-gallon steel tank, known as a tote, with ethyl acetate, a flammable solvent. The operator had secured the fill nozzle with a steel weight and had just walked across the room when he heard a “popping” sound and turned to see the tote engulfed in flames. Employees tried unsuccessfully to extinguish the fire with a handheld fire extinguisher before evacuating.
The CSB found that the nozzle and hose were not intended for use in transferring flammable liquids, and the steel parts of the fill nozzle and hose assembly were not bonded and grounded. “In this case, all the conductive metal objects in the nozzle and hose, and the steel weight that was suspended from the handle by a wire, were all isolated from ground and were susceptible to static accumulation and discharge,” said CSB Lead Investigator Randy McClure.
The packaging area, where the fire started, had no automatic sprinkler system and was adjoined to the flammable storage warehouse. The investigation found that the wall separating the two areas was not fire rated. As a result, the warehouse was rapidly consumed, and although this area had an automatic sprinkler system, it was incapable of extinguishing the large blaze.
The CSB recommends that facilities ensure that equipment used to transfer liquids is properly bonded and grounded; that fire suppression systems should be installed in packaging areas; and that packaging to be used for flammable liquids, such as portable steel tanks, be separated from bulk storage areas by fire-rated walls and doors.