Overhead Crane Wire Rope Selection: The Complete Guide to Safe Drum and Sheave Design

Wire rope, drums, and sheaves are the core components of any overhead crane or hoist lifting mechanism. When specifying these components, what minimum safety factor should you use? How do you calculate the required minimum breaking force? What diameter should your drum and sheave be?

Overhead Crane Wire Rope Selection explained with GB/T 34529-2017 (ISO 16625). Learn how to calculate minimum breaking force, choose the correct wire rope safety factor, determine drum and sheave diameters, control fleet angles, select groove dimensions, and optimize wire rope performance for overhead crane and hoist applications.

1. Scope

This standard applies to the following crane and hoist types (most are defined in ISO 4306-1, corresponding to GB/T 6974.1-2008):

• Bridge cranes (overhead cranes)
• Wire rope hoists
• Portal or semi-portal cranes
• Gantry or semi-gantry cranes
• Cable cranes and portal cable cranes (lifting mechanism and trolley travel mechanism only)
• Mobile cranes
• Tower cranes
• Railway cranes
• Floating cranes
• Deck cranes
• Derrick cranes and cable-type derrick cranes
• Rigid-braced derrick cranes
• Jib cranes (pillar, boom, wall, or bicycle type)
• General offshore cranes

2. Overhead Crane Wire Rope Minimum Safety Factor Zp

The minimum safety factor for an overhead crane wire rope depends on the mechanism work duty, rope application, reeving arrangement, and rope type.

Items 1–5 are sourced from GB/T 3811-2008 Table 44; items 6–9 are sourced from GB/T 34529-2017 and GB/T 8706-2017.

Key supplementary notes:

1. For wire ropes handling hazardous loads, select the safety factor from the table at one work-duty level higher than the design classification.
2. For metallurgical cranes and port container cranes with mechanism work duties M7 or M8, a slightly lower work-duty classification may be used for wire rope selection, provided that rope deterioration can be monitored during service to ensure safe use and timely replacement.
3. Metallurgical cranes: the minimum safety factor shall not be less than 7.1.
4. Port container cranes: the minimum safety factor for main hoist ropes and trolley traction ropes shall not be less than 6.
5. Wire ropes for telescopic booms shall have a safety factor of not less than 4.
6. Standard wire rope — A collective term for “single-layer strand rope” and “parallel-closed rope”, also referred to as “non-rotation-resistant rope”.
7. Rotation-resistant wire rope — A multi-strand rope that produces reduced torque or rotation when supporting a load. Rotation-resistant ropes generally consist of at least two layers of strands laid helically around a steel strand core or fibre core, with the outer strands laid in the opposite direction to the adjacent inner strands.

1. Single-layer strand rope — A multi-strand rope consisting of one layer of strands laid helically around a core.

1. Parallel-closed rope — A multi-strand rope consisting of two or more layers of strands laid in a single operation around a strand core or fibre core.

Mobile cranes include truck cranes, wheel-type cranes, crawler cranes, all-terrain cranes, and lorry-mounted cranes (GB/T 20776-2023).

3. Overhead Crane Wire Rope Selection

3.1 Minimum Breaking Force

Fmin ≥ S × Zp

Special handling for grab-bucket cranes:

3.2 Maximum Fleet Angle

Measures to reduce fleet angle:

• Increase drum diameter to reduce the winding range
• Increase the distance between sheave and drum

3.3 Maximum Service Temperature for Wire Rope

4. Overhead Crane Drum and Sheave Selection

4.1 Drum Type and Winding Direction

Winding direction rules:

• Plain drum → The winding direction depends on the rope lay direction; determine the rope fixing point per Table 4.
• Grooved drum → Either rope lay direction may be used, but the same lay as for a plain drum is preferred: left-hand helical groove matches right-hand lay rope, right-hand helical groove matches left-hand lay rope.

4.2 Groove Radius and Sheave Material

Sheave material selection guidelines:

For frequent service: use steel sheaves to increase the likelihood of external wear — this wear facilitates rope inspection. If polymer sheaves are used, it is recommended to include at least one steel sheave in the reeving arrangement, usually the one closest to the drum.

4.3 Minimum Drum and Sheave Diameter

5. Special Operating Conditions

For molten metal handling, extremely severe and/or corrosive environments, and similar special conditions:

1. The mechanism work duty shall not be lower than M5
2. The Zp value shall be increased by 25%, up to a maximum of 9.0

The original document also covers the use of swivels and swivel joints, causes of wire rope deterioration, rope elongation and selection, and rope termination selection. Refer to the original standard for further study.

Reference standards(Query of Chinese Crane Standards):

• GB/T 34529-2017 Cranes and hoists — Selection of wire ropes, drums and sheaves (IDT ISO 16625:2013)
• GB/T 20118-2017 Steel wire ropes for general purposes (NEQ ISO 2408:2017)
• GB/T 20863.1-2021 Cranes — Classification — Part 1: General (IDT ISO 4301-1:2016)
• GB/T 6974.1-2008 Cranes — Vocabulary — Part 1: General (IDT ISO 4306-1:2007)
• GB/T 5972-2023 Cranes — Wire ropes — Care and maintenance, inspection and discard (IDT ISO 4309:2017)
• GB/T 8706-2017 Steel wire ropes — Vocabulary, designation and classification (MOD ISO 17893:2004)

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