ISO 24445:2020 Crane Wire Rope Selection Requirements
ISO 24445:2020 — "Cranes — Wire Rope Selection Requirements" is the governing standard for crane wire rope selection. Building on ISO 4308, it adds refined selection criteria for diverse operating conditions, including special performance requirements such as high-temperature resistance, corrosion resistance, and rotation resistance.
Selecting the Right Wire Rope Construction
ISO 24445:2020 specifies the preferred wire rope constructions for crane applications — round-strand ropes with regular lay in 6×19+FC or 6×37+FC configurations are the first choice. For applications requiring rotation resistance, multi-layer strand rotation-resistant ropes or spiral ropes are recommended. For Metallurgical Foundry Cranes operating in high-temperature environments, heat-resistant wire ropes with specially treated steel wires and heat-resistant coating are specified, suitable for service temperatures up to 300°C. In corrosive environments such as port and marine cranes, galvanized wire ropes with a zinc layer weight of at least 200 g/m² or stainless steel wire ropes are recommended. For Tower Cranes with lifting heights exceeding 100 m, compacted strand wire ropes or spiral ropes are recommended to minimize multi-layer winding on the drum. The recommended nominal tensile strength is 1770 N/mm²; for ultra-large tonnage cranes where dead weight reduction is critical, 1960 N/mm² may be selected, though bending fatigue life will be correspondingly reduced.
Wire Rope Diameter Calculation
The standard defines two methods for determining wire rope diameter. Method 1 is based on minimum breaking force: Fmin ≥ S × Zp, where S is the maximum working load on the rope (including lifting load and rope dead weight) and Zp is the minimum safety factor. Method 2 uses a diameter coefficient: d ≥ C × √S, where C is the diameter selection coefficient that depends on the work duty classification and wire rope construction. The larger value from the two methods governs. Safety factors by classification — M1~M2: 3.55, M3: 4.0, M4: 4.5, M5: 5.0. For special working conditions — high-temperature environments require an additional 0.5 above the base classification factor. Cranes used for personnel lifting require a safety factor of at least 6. The calculated diameter must be rounded up to the nearest standard size — 8/10/11/12.5/14/16/18/20/22/24/26/28/30 mm, etc. Rounding down is not permitted.
| Work Duty / Classification | Safety factor Zp | Diameter Coefficient C | Application |
|---|---|---|---|
| M1~M2 | 3.55 | 0.080 | Manual/Light Duty |
| M3 | 4.0 | 0.086 | Medium Duty |
| M4 | 4.5 | 0.092 | Heavy Duty |
| M5 | 5.0 | 0.100 | Extra Heavy Duty |
| Personnel | ≥6.0 | 0.110 | Personnel Lifting and transport |
Drum & Sheave Matching for Wire Rope
After selecting the wire rope, the D/d ratio for the drum and sheaves must be verified—drum D≥18d, hoisting pulley ≥18d, and equalizer sheave ≥12d. For rotation-resistant or spiral wire ropes, the D/d ratio should be ≥20. The drum groove radius should be approximately R≈0.53d–0.56d, with groove depth ≥0.25d and groove pitch between 1.05 and 1.1d. For lay direction, right regular lay (ZS) is the most commonly used. When fixing the wire rope end with clamp plates, at least two clamping plates are required; for wedge sockets, the wedge must be fully seated. Kelude Heavy Industry strictly follows ISO 24445:2020 in wire rope selection, choosing the most suitable rope type and specification based on the operating environment and conditions.
| Check Items | requirements | applicable conditions |
|---|---|---|
| Drum D/d | ≥18(Standard)/≥20(Spiral Strand Rope) | All |
| Pulley Dp/d | ≥18(Hoisting / Lifting)/≥12(Balance) | All |
| rope groove radius | R=0.53~0.56d | All |
| rope groove Depth | ≥0.25d | All |
| rope groove Spacing | 1.05~1.1d | All |
FAQ
Q: What does ISO 24445:2020 require for wire rope selection under special working conditions?
A: Use heat-resistant wire rope for high-temperature environments (≤300°C), galvanized rope (≥200g/m²) for corrosive atmospheres, compacted strand or spiral rope for lifting heights exceeding 100 m, and a safety factor of at least 6 for personnel lifting. Regular lay 6×19 or 6×37 constructions are preferred.
Q: What are the two methods for determining wire rope diameter?
A: The breaking force method (Fmin ≥ S × Zp) and the diameter coefficient method (d ≥ C × √S), taking the larger value. Safety factor M4 ≥ 4.5, M5 ≥ 5.0, and ≥ 6.0 for personnel lifting. Always round the diameter up, never down.
Q: How are special safety factors determined?
A: Add 0.5 to the M5 value for high-temperature environments. Personnel-lifting cranes require a safety factor of at least 6.0. Kelude configures safety factors one grade above the standard to ensure maximum reliability.
Q: How do you verify drum and sheave compatibility?
A: Drum ratio D/d ≥ 18 (≥ 20 for spiral rope), hoisting pulley ratio Dp/d ≥ 18, and equalizer sheave ratio ≥ 12. Rope groove radius R = 0.53–0.56d, depth ≥ 0.25d, and pitch 1.05–1.1d. Kelude selects and matches components according to the standard.
