By TEBAOFLEX Jyen. Originally published on September 5, 2026.
Corkscrewing is a change in cable shape that can indicate accumulated twist, unstable basket handling or internal displacement. Intermittent optical loss may occur at the same time, but a deformed cable is not the only possible cause. Connectors, contamination, splices and unsupported transitions also need investigation.
Start with the movement history
- Record hoist position, trolley position, travel direction, speed and the moment an optical alarm occurs.
- Compare the installed cable designation with the manufacturer’s stated basket, reeling or festoon duty. These handling modes are not interchangeable.
- Photograph the basket entry, coil pattern, guides, clamps and terminations while the equipment is safely isolated.
- Check changes after a cable replacement, basket repair or route alteration before attributing every failure to fibre material.
One full revolution is 360 degrees, or 2π radians. The twist introduced by a particular coil-handling arrangement depends on payout and take-up geometry; it is not established by counting coils alone. Cable suppliers may design special basket constructions, but their ratings do not automatically apply to a visually similar cable.
Separate optical events from mechanical symptoms
Clean and inspect accessible connectors using the appropriate procedure. Establish a repeatable end-to-end insertion-loss baseline at wavelengths suited to the installed fibre and equipment. An OTDR can help locate events, but launch/receive leads, dead zones, resolution and short cable length affect interpretation. A small event change on a short crane cable should not be presented as a precise distributed dB/km measurement.
Repeat measurements at safely controlled positions where faults previously occurred. Record temporary loss while moving and residual loss after the cable returns to its reference position. A stable average can conceal short interruptions; monitoring speed must suit the application.
Do not solve routing errors by changing fibre designation alone
G.657 describes bending-loss-insensitive single-mode fibre characteristics. It does not certify the complete cable against tensile loading, repetitive twisting or basket handling. OM3 and OM4 are multimode categories; substituting them requires compatible transmitters, receivers and link design, not merely a favorable bend claim.
Review the cable’s dynamic bending radius at the actual tension and temperature, guide geometry, bend reversals and termination strain relief. Radius, sheave diameter and spacing between opposite bends are different dimensions and must be identified explicitly on drawings.
Corrective action and acceptance
- Have the cable and handling-system suppliers agree the coiling direction, basket geometry, allowable torsion and installation procedure.
- Isolate and secure the machinery before inspection. Do not freely suspend a heavy cable or force a damaged cable straight without an approved handling plan.
- Assess bulges, sheath damage and suspected internal displacement before returning a cable to service; there is no universal safe number of untwisting cycles.
- Retain baseline optical traces, electrical checks, photographs and an agreed functional movement test after corrective work.
A purchase specification should identify the actual spreader movement and optical link budget, with representative qualification evidence for the offered construction. A generic flexible-conductor designation does not establish basket endurance.
Sources and scope
UTV: a purpose-designed basket cable
ITU-T G.657: bending-loss-insensitive single-mode fibre
These references explain the relevant methods or manufacturer guidance. They do not certify a TEBAOFLEX product or establish results for a supplied batch.
Discuss your specification
For a project-specific cable specification, send the duty, installation drawing and required acceptance criteria to TEBAOFLEX. WhatsApp: +86 185 9591 3361. Request documented product ratings and test evidence before approval.