Open-Tank Mix of Flammable Solvents Caused Explosion, CSB Concludes

Two workers from Universal Form Clamp Co., based in Bellwood, Ill., were injured as a result of the blast that occurred on June 14. Eyewitnesses told CSB investigators the two injured men were not in the mixing rooms but in adjacent work areas. According to CSB interviews, the fatally injured worker who suffered burns over 90 percent of his body was a delivery driver not employed by Universal Form Clamp.

During the investigation, CSB found that at the time of the incident there were approximately 11,000 pounds of heptane a highly flammable and volatile liquid and mineral spirits in the open tank.

During the heating process there was a sudden evolution of flammable vapors from the tank. The vapors ignited, causing an explosion and fire. Combustible chemicals stored nearby also caught fire and burned for 2 hours until the blaze was extinguished by local firefighters.

CSB Board Member John Bresland said the agency will continue its investigation.

"The board is concerned about the practice of mixing and heating flammable liquids in open tanks without appropriate safeguards," he said. "Our investigation will examine facility procedures as well as the adequacy of fire codes, standards and local permitting and enforcement.'

Universal Form Clamp Co. is a manufacturer and supplier of construction products and chemicals. The facility changed ownership about 6 weeks prior to the incident. The company has been cooperating fully with the investigation, according to CSB.