During the early morning hours of January 25, ASCO employees filled cylinders with purchased acetylene. At approximately 9:30 am, with the depletion of the supply of purchased acetylene, they began to produce acetylene from calcium carbide in the generator.

Because of heavy snowfall, workers were shoveling snow in the area south of the decant tanks near the loading dock. At 10:36 am, an explosion occurred, centered in the shed. Two of the workers immediately south of the shed were killed instantly. A third worker farther south, closer to the loading dock, was severely injured and was pronounced dead shortly after arriving at the Newark Medical Center. A fourth worker who was in the loading dock/lime pit area was very seriously injured by the blast. .

KEY ISSUES:
• OPERATING PROCEDURES
• STAFF TRAINING
• DRAIN & VENT TO SAFE LOCATION
• BUILDINGS TO BE DESIGNED FOR ACETYLENE CONTAINMENT
• MECHANICAL INTEGRITY
• POSITIVE ISOLATION

ROOT CAUSES:
1. At ASCO, a line that could potentially contain acetylene drained into an enclosed wooden shed.
2. The shed in this incident was not designed or constructed in accordance with NFPA 51A.
3. At ASCO the check valve was relied upon to prevent backflow. The check valve and block valve that failed at ASCO and allowed backflow were not on a testing or inspection schedule. The single block valve on the recycle water line, which was found closed after the explosion, leaked during post-incident testing.
4. Operators did not use either written operating procedures or check lists for start up of the acetylene generator or recycled water system at this facility.

Image Credit: CSB