Rigging Design, Load Movement, and Critical Lift Planning
Core concepts
A critical lift plan is a written, engineered document. Candidates must know what makes a lift critical (near capacity, multiple cranes, personnel under load, unusual configuration, hazardous loads), the elements of a lift plan (load weight and CG, rigging diagram, capacity checks, ground conditions, communication, contingency), and the principle of load movement control - tag lines, controlled descent, and avoidance of swing. Also: two-crane lifts require load-sharing analysis and a designated lift director.
Traps in questions
- Treating a lift plan as a checklist rather than an engineered analysis.
- Ignoring ground bearing and underground utilities.
- Assuming two cranes share load equally - they rarely do; geometry and CG drive the split.
- Forgetting environmental limits (wind, visibility).
Rule of thumb
If any element is unusual - near capacity, multi-crane, personnel, or hazardous - treat it as critical and require engineering review and a written plan.
Worked example
A two-crane pick of a 30,000 lb vessel: the CG is closer to crane A, so A carries 18,000 lb and B carries 12,000 lb. Each crane's chart must be checked at its actual radius and configuration, with a lift director coordinating. Equal-share assumptions are a common and dangerous error.