Overview
ISO 21669:2005 specifies a standardized method to determine the rotational properties of steel wire ropes. The method gives manufacturers, independent test laboratories and lifting-equipment designers a repeatable procedure to measure cable rotation under load. Results are expressed as the number of turns per unit length (normalized to 1 000d, where d is the nominal rope diameter in millimetres).
This standardized test is primarily intended to support decisions about the use of swivels or other anti-rotation devices with hoist and crane ropes and to inform cable selection where rotation behaviour under load is important.
Key Topics
- Specimen requirements: Test specimens must be representative of the complete rope, free from defects and independent of the rope used to lift the test load. The free length between terminations shall be at least 100 × d (d = nominal rope diameter).
- Terminations allowed: Swaged socket, resin or metal-filled sleeves, wedge sockets, eye terminations or ferrule and thimble arrangements as appropriate.
- Test load: The mass of the test load must be at least 20% of the rope's minimum breaking force (F_min). If the test mass exceeds 20% of F_min, the measured rotation is not adjusted for the overload.
- Measurement method: A needle is attached to the lower end of the specimen or load to indicate rotation against a graduated dial (graduations must not exceed 45°). During lifting, the number of full turns and angular deviation are recorded when the load reaches equilibrium.
- Normalization: Observed rotations are converted to an equivalent value for a length of 1 000d by direct proportion (for example, 1 turn measured on a 250d free length equals 4 turns per 1 000d).
- Reporting: Test reports must include number of tests, reference to ISO 21669:2005, cable designation and F_min (kN), rotation value in turns per 1 000d, and test load (tonnes).
Applications
The measured rotational property supports practical decisions and safety assessments in:
- Crane and hoist rope selection and specification
- Determination of whether a swivel (rotule) can be used with a given rope
- Factory and type testing by rope manufacturers and independent test houses
- Operational safety reviews and lift planning where load rotation is a hazard
Annex A of the standard provides practical guidelines on swivel use based on rotation results:
- <= 1 turn/1 000d at 20% F_min: a swivel may be used
-
= 1 and <= 4 turns/1 000d at 20% F_min: swivel use depends on manufacturer guidance or competent approval
-
= 4 turns/1 000d at 20% F_min: swivel use is not recommended
Related Standards
- ISO 17893 - Steel wire ropes: vocabulary, designation and classification (referenced by ISO 21669:2005).
For effective implementation, test results from ISO 21669:2005 should be used alongside equipment manuals and lifting-equipment safety procedures to ensure correct swivel selection and safe lifting operations.