Model line pull, parts of line, and losses. Validate duty, angle, and layer effects. Get clear capacity margins for safer lifts every time onsite.
| Scenario | Rated line pull (kN) | Parts of line | Efficiency | Derating (duty×angle×layer) | Load (kN) | Dynamic factor | Allowable (kN) | Margin (kN) |
|---|---|---|---|---|---|---|---|---|
| Typical lift | 10.0 | 2 | 0.88 | 0.90 | 8.0 | 1.10 | 15.84 | 7.04 |
| High angle loss | 10.0 | 2 | 0.88 | 0.75 | 8.0 | 1.20 | 13.20 | 3.60 |
| Heavier load | 12.0 | 2 | 0.88 | 0.85 | 14.0 | 1.15 | 17.95 | 1.85 |
These examples are illustrative. Always follow manufacturer instructions and site lifting plans.
1) Combined derating factor
Derating = Efficiency × Duty factor × Angle factor × Layer factor
2) Effective allowable load
Allowable = Rated line pull × Parts of line × Derating
3) Dynamic demand
Dynamic demand = Load × Dynamic factor
4) Safety margin and utilization
Margin = Allowable − Dynamic demand, and Utilization = (Dynamic demand ÷ Allowable) × 100%
Hoists support critical lifts in maintenance bays, structural erection, equipment installation, and material handling. A practical capacity check is not only about the nameplate rating. Real jobsite performance is reduced by reeving losses, fleet-angle effects, drum-layer changes, duty cycle, and dynamic events such as starting, stopping, snags, and load swing. This calculator organizes these influences into one transparent workflow so planners can document assumptions and confirm that the selected setup has adequate reserve.
Start by entering the rated line pull provided by the manufacturer, then set the parts of line for your reeving arrangement. More parts of line increase mechanical advantage, but each sheave introduces friction. That is why the reeving efficiency is applied as a multiplier rather than assuming perfect force transfer. Next, apply derating factors that reflect field conditions: duty factor for heat and repetition, angle factor for side loading and fleet angle, and layer factor for reduced pull on higher drum layers.
The calculator then compares effective allowable load against dynamic demand. Dynamic demand is computed by multiplying the total load (including rigging, hooks, spreaders, and below-hook devices) by a dynamic factor. When lifts involve frequent starts, sudden stops, or potential snags, choose a higher dynamic factor. The output includes a safety margin and utilization percentage so you can quickly judge how close the lift is to the adjusted limit.
Example data: suppose a wire rope hoist has a rated line pull of 10 kN, reeved with 2 parts of line, and a reeving efficiency of 0.88. If duty×angle×layer derating is 0.90, the combined derating becomes 0.792. The effective allowable load is 10 × 2 × 0.792 = 15.84 kN. For an 8 kN total load with a dynamic factor of 1.10, dynamic demand is 8.80 kN, leaving a margin of 7.04 kN. This reserve is useful for minor configuration changes, but it is still good practice to keep utilization comfortably below 100% for routine lifts.
Use the CSV or PDF export to attach capacity checks to lift plans, permits, and inspection packs. Always follow the manufacturer’s limits, site procedures, and qualified rigging supervision for final approval.
It is the manufacturer’s specified pull on the line under stated conditions, often tied to drum layer, speed, and reeving. Use the official manual or nameplate, not estimates from similar equipment.
More parts of line provide mechanical advantage, reducing the required pull per line segment. However, extra sheaves add friction, so efficiency must be considered to avoid overestimating capacity.
Use higher values when shock loading is possible: rapid starts, sudden stops, snagging, wind-induced swing, or poor control. Use lower values only for smooth, well-controlled lifts with minimal disturbance.
Angle factor derates capacity for side loading, fleet angle, and misalignment that increase friction and reduce effective pull. If the line does not run straight, apply a conservative angle factor.
As wire rope builds up on a drum, the effective drum diameter increases and available pull can decrease. Layer factor is a practical adjustment to reflect reduced performance on upper layers.
No. It is a simplified force–velocity estimate to support planning. Motor sizing should include drivetrain losses, duty rating, starting currents, thermal limits, and manufacturer guidance.
It supports documentation and screening, but it does not replace engineered lift planning. Always confirm rigging, structural support, travel path, clearances, and supervision requirements before execution.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.