Execution of Complex Lifts
Complex and Critical Lifts
Complex lifts are the ones where the standard chart-and-hook routine stops covering you: multiple cranes, tailing and upending, lifts over occupied space or hazardous materials, unusual rigging configurations, and lifts near the top of the capacity chart. Many employers define a critical lift at 75% or more of rated capacity at the actual radius, and require a written or engineered plan, a pre-lift meeting, and a dedicated supervisor.
In a two-crane or tailing operation, the load is shared dynamically. As a vessel rotates from horizontal to vertical, the tailing crane's share drops while the main crane's share rises, so each crane must be checked against the worst point in the rotation, not the starting point. The plan must define rigging geometry, the load-sharing assumption, communications, and the stopping point if anything drifts.
Load control equipment - load moment indicator, rated capacity limiter, anti-two-block - must be functional and never overridden to "get it done." Wind, side loading, and rapid swing start and stop add forces the chart does not show.
Trap: candidates assume the tailing crane's load stays constant, or that a two-crane lift is simply two single-crane lifts side by side.
Rule of thumb: any lift at 75% of chart capacity gets a written plan, a dry run, and a pre-lift meeting with everyone who will touch the load.