Tandem (Two-Crane) Lift Load Share
Each crane's share of a tandem lift from the CG, the derated allowable per crane, and a combined pass / fail.
Example
You enter
- Total load weight (lb) 40000
- Span between crane picks (in) 300
- Distance from crane 1 to CG (in) 120
- Per-crane derate (percent) 75
- Crane 1 net capacity (lb) 28000
- Crane 2 net capacity (lb) 24000
You get
- Share c1 24000
- Share c2 16000
- Allow c1 21000
- Allow c2 18000
Checked against published worked examples from: ASME B30.5 / OSHA 1926 Subpart CC.
Details, formula, and sources
ScopeA designated lift director and an engineered plan govern.
Formula or tableshare_c1 = W x (span - cg) / span; share_c2 = W x cg / span; allow = net_chart x derate / 100; pass when each share <= its derated allowable.
Source and editionASME B30.5 and OSHA 1926 Subpart CC by name; the cg-load-share statics plus a per-crane tandem derate.
Free accessOSHA 1926 Subpart CC is free at osha.gov; ASME B30.5 is a consensus standard. The capacities come from each crane's load chart.
What governsEstimate. Head rigger and manufacturer working-load-limit charts govern. Inspect every piece of hardware before the show.
API field namestotal_weight_lb, span_in, cg_from_c1_in, derate_pct, c1_chart_lb, c2_chart_lb, share_c1, share_c2, allow_c1, allow_c2
- Tandem derate 75% of each crane's net chart capacity (planning default)rigging planning practice