Crane Lift Plan Quick-Math
Gross load, sling tension, percent of chart, and 75 / 90 percent flag.
Example
You enter
- Load (lb) 8000
- Rigging (lb) 200
- Sling legs (n) 2
- Sling angle (deg) 60
- Chart capacity for this configuration (lb) 12000
You get
- Gross load 8200 lb
- Per-leg sling tension 4619 lb
- Chart capacity (lb) 12000
- Percent of chart 68.3 %
- Flag GREEN
Details, formula, and sources
The crane manufacturer's load chart governs.
Gross load = load + rigging + block + jib_deduct. Per-leg sling tension L = W / (n × sin(theta)) with the sling angle theta measured from horizontal (vertical pick theta = 90 deg gives W/n; tension diverges as the sling flattens). Percent of chart = gross / chart_capacity × 100. Flags: < 75% green, 75-90% yellow, ≥ 90% red. Refuses to render an output without the user-entered chart capacity (the tool never reproduces a load chart).
ASME B30.5 (Mobile and Locomotive Cranes) by name and section. ASME B30.9 (Slings) for the per-leg formula. OSHA 29 CFR 1926 Subpart CC (cranes and derricks) by section.
ASME B30 series licensed; OSHA 29 CFR 1926 free at ecfr.gov.
Estimate. Engineer of record governs the design and acceptance. Verify against the project structural drawings and the manufacturer's published capacity / chart.
Field names used by the API: load_lb, rigging_lb, sling_legs, sling_angle_deg, chart_capacity_lb, gross_load_lb, per_leg_lb, percent_of_chart, flag
- Per-leg formula L = W / (n × sin(theta)) with theta the sling angle from horizontal; vertical pick (theta = 90 deg) L = W / nASME B30.9
- Critical-lift threshold 75% of chart capacity (engineering-practice critical-lift trigger)engineering practice