Incident Report - Mississippi, USA

Multiple cranes were engaged to lift and place a 250-tonne bow unit for the assembly of a large supply vessel at a Mississippi shipyard. The tandem ‘lift and travel’ maneuver required two Manitowoc 16000 Crawler Cranes to lift, travel and align in unison.

When one crane pulled ahead of the other, the second Manitowoc tipped forward. While the operator attempted to recover, the massive weight meant the crane’s load slipped, crushing the cab and throwing the operator through the windshield in the process. The operator suffered a broken pelvis and crushed skull. While he survived, he suffered a traumatic brain injury. He is now blind and has severely reduced mental capacity. One of the cranes fell into a warehouse building at the VT Halter shipyard, injuring four others.

The shipyard bore most responsibility for the accident. The jury’s verdict found Manitowoc should bear 40 percent of the responsibility, and the operator, 10 percent. The shipyard was cited with four serious violations due to the absence of clearly visible load charts; exceeding the rated load capacity; the designated person did not ensure proper positioning of spotters and did not ensure the cranes made the predetermined movements; and failing to load test the lower load cell sensor on the main hoist after it was repaired.

Key learnings from this incident

With multiple cranes working in tandem, both the movement of the load and crane travel needs to be perfectly choreographed. Traveling means that dynamic forces come into play when synchronisation is off. Being off by the slightest amount can result in a catastrophic imbalance. This incident shows how terribly wrong a tandem lift can go when load planning failures are compounded by inadequate sensor and positioning information being available to the operator.