| Problem |
Cause/Action |
| Mechanical
damage caused by the rope contacting the structure of the crane on
which it is operating or an external structure - usually of a localized
nature. |
- Generally results from operational conditions.
- Check sheave guards and support/guide sheaves to ensure that the rope has not jumped out of the intended reeving system.
- Review operating conditions.
|
Opening
of strands in Rotation Resistant ropes - in extreme circumstances
the rope may develop a "birdcage distortion" or protrusion
of inner strands.
Note - Rotation Resistant ropes are designed with a specific strand
gap which may be apparent on delivery in an off tension condition.
These gaps will close under load and will have no effect on the operational
performance of the rope. |
- Check
sheave and drum groove radii using sheave gauge to ensure that
they are no smaller than nominal rope radius +2.5% - Bridon recommends
that the sheave and drum groove radii are checked prior to any
rope installation.
- Repair or replace drum/sheaves if necessary.
- Check fleet angles in the reeving system - a fleet angle in excess of 1.5 degrees may cause distortion (see Fleet Angle).
- Check installation method - turn induced during installation can cause excessive rope rotation resulting in distortion (See Product Safety: Handling & Installation).
- Check if the rope has been cut on site prior to installation or cut to remove a damaged portion from the end of the rope. If so, was the correct cutting procedure used? Incorrect cutting of rotation resistant, low rotation and parallel closed ropes can cause distortion in operation (See Product Safety: Handling & Installation).
- Rope may have experienced a shock load.
|
Broken
wires or crushed or flattened rope on lower layers at crossover points
in multi - layer coiling situations.
Wire breaks usually resulting from crushing or abrasion. |
- Check tension on underlying layers. Bridon recommends an installation tension of between 2% and 10% of the minimum breaking force of the wire rope. Care should be taken to ensure that tension is retained in service. Insufficient tension will result in these lower layers being more prone to crushing damage.
- Review wire rope construction. Dyform wire ropes are more resistant to crushing on underlying layers than conventional rope constructions.
- Do not use more rope than necessary.
- Check drum diameter. Insufficient bending ratio increases tread pressure.
|
| Wires looping from strands. |
- Insufficient
service dressing.
- Consider
alternative rope construction.
- If
wires are looping out of the rope underneath a crossover point,
there may be insufficient tension on the lower wraps on the drum.
- Check
for areas of rope crushing or distortion.
- Possible
fleet angle problems causing rope rotation.
|
| Pigtail or severe spiralling in rope. |
- Check that the sheave and drum diameter is large enough - Bridon recommends a minimum ratio of the drum/sheave to nominal rope diameter of 18:1.
- Indicates that the rope has run over a small radius or sharp edge.
- Check to see if the rope has jumped off a sheave and has run over a shaft.
|