The crane wire rope is the most fatigue-exposed element of the hoisting mechanism. A rope not replaced in time can break, dropping the load and causing serious accidents. ISO 4309 and FEM 1.001 clearly define the rope discard criteria.
When Should the Rope Be Replaced? (Discard Criteria)
- Six or more broken wires within any one lay length of a 6-strand rope
- Permanent diameter reduction exceeding 7% (wear or deformation)
- Kink, loop or crushing damage on the rope
- Corrosion affecting 50% of the surface area
- Permanent distortion caused by layer pressure on the drum
Rope Replacement Procedure
- 1Safe isolation: LOTO is applied and the hook is brought to an unloaded position.
- 2Releasing the old rope: The rope is carefully unwound from the drum and sheaves; the rope end is released.
- 3Cleaning the drum: The drum grooves and flanges are inspected; if deformed, replacement is decided.
- 4Preparing the new rope: The same diameter, lay direction and construction code (e.g. 6×36 IWRC) are selected; the manufacturer’s pre-tensioning advice is followed.
- 5Reeving the rope: The new rope is reeved in the correct direction and fixed to the drum, leaving at least 2 dead wraps at the flange.
- 6Tensioning test: Pre-tension is established by running several full lower/raise cycles at slow speed.
- 7Load test and record: A rated-capacity test is performed and the replacement date and details are logged in the maintenance record.
Frequently Asked Questions
Why is lay direction important in rope replacement?
The wrong lay direction causes rope twisting and rapid fatigue. The drum groove and rope lay direction (right lay / left lay) must match. This should be noted before the old rope is removed, or checked in the crane’s technical documentation.