KEVOS® MAKEOS · Mechanics
Wire Rope Reeving: Line Pull and Safety Factor
What pull is on the hoist rope with this reeving, and is the rope’s safety factor enough?
Line pull at the drum for a load reeved over several parts of line with sheave friction, the rope safety factor against its minimum breaking load, and the sheave-to-rope diameter ratio.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Load mass (including hook block) | kg | Mass lifted including the hook block and slings. |
| Parts of line supporting the load | parts | Number of rope falls between the upper and lower blocks. |
| Efficiency per sheave | % | Efficiency of each sheave (about 98% for rolling bearings, 96% for plain bushes). |
| Rope minimum breaking load | kN | Minimum breaking load from the rope certificate. |
| Required rope safety factor | Rope design factor required by your crane or hoist code (often 5 or more). | |
| Sheave pitch diameter | mm | Pitch diameter of the smallest sheave. |
| Rope diameter | mm | Nominal rope diameter. |
| Required minimum D/d | Minimum sheave-to-rope ratio from the code or rope maker. |
Method and formulas
- Line pull F = W (1 − η) ÷ (1 − ηⁿ), with W = m g.
- Reeving efficiency = W ÷ (n F).
- Safety factor = MBL ÷ F; D/d = sheave ÷ rope diameter.
- Example: 5000 kg on 4 parts gives 12.632 kN line pull and a safety factor of 9.4995.
Limitations
- Hoisting at steady speed; acceleration, dynamic and wind loads must be added per the code.
- Lead and equaliser sheaves outside the block are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check hoist rope and drum pull for a block
- Choose the number of parts of line
- Check sheave size against the rope
Who it is for
- Lifting engineers
- Maintenance engineers
- Crane and hoist designers
What you get
- Line pull at the drum
- Rope safety factor
- Reeving efficiency
- Sheave D/d ratio
Interpreting the result
- Lifting equipment must meet its design code and be certified by a competent person.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2613–2650. Topic reference; no source tables or recommended settings are reproduced.
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