Inspection Detail

Inspection: 303391973 - National Paving Company, Inc.

Inspection Information - Office: Marlton Area Office

Investigation Summary

At approximately 4:30 p.m. on June 26, 2001, Employee #1 was performing his daily end of day clean up procedures at an asphalt manufacturing plant. One of his duties was to spray approximately half gallon of Number 2 fuel oil onto the flights of the two enclosed conveyors that carry the asphalt from the plant's asphalt mixing drum to the asphalt silos. While the conveyor was running, the Number 2 fuel oil was applied to the conveyor through an opening at the base of the first conveyor where the hot asphalt enters the conveyor from the mixing drum. Once the entire conveyor had been coated with the Number 2 fuel oil, Employee #1 used a metal scraper to remove some of the excess asphalt from it. A second coating of Number 2 fuel oil was applied. This application softened any residual asphalt on the conveyor and helped to prevent it from hardening over night. Although the Number 2 fuel oil is not flammable at ambient temperatures, when applied to the residual asphalt, the Number 2 fuel oil's flash point was exceeded. The temperature was approximately 300 degrees Fahrenheit when it enters the conveyor. The vapors accumulated in the conveyor's enclosures until it was ignited (source of ignition was undetermined). The conveyor enclosure exploded, shearing the 0.5 inch bolts that held the metal cover plates on it. The plates blew over the top of the plant and landed approximately 350 feet away. The plates weighed several hundred pounds each. Employee #1 had minor cuts and was treated at a local hospital later that evening.

Keywords: FLAMMABLE VAPORS, EXPLOSION, LACERATION, CONVEYOR, ASPHALT