Three workers were killed in an explosion at the Packaging Corporation of America (PCA) fiberboard manufacturing facility while they were welding on a temporary metal clamp to stabilize a damaged flange connection. The flange was located on top of an 80-foot tall storage tank that contained recycled water and fiber waste.

Facility personnel were unaware of the potential presence of flammable gas from the decomposition of the organic material in the tank, and combustible gas monitoring was not typically required or performed prior to starting work. At the time of the accident, three workers were on a catwalk above the tank; one began welding the flange into place when sparks from the welding ignited flammable vapors inside the tank. The resulting explosion ripped open the tank lid, knocking two of the workers to the ground 80 feet below. All three workers died of traumatic injuries. A fourth worker, who had been observing the work from a distance, survived with minor injuries.

KEY ISSUES:
• ANALYZE THE HAZARDS
• MONITOR THE ATMOSPHERE
• TEST THE AREA

ROOT CAUSES:
1. Anaerobic bacteria
2. Hot work

Image credit: CSB