Frequent Luffing Wire Rope Damage Issue

frzing8585 · Apr 20, 2016

It is observed that the Wire Rope used for the Luffing Operations of our Crane is getting frequently damaged (2-3 Months - 100hrs of Working). There were no fouling observed at any point on the Crane and the Fleeting Angle is also within acceptable limits (0.7 Degrees as per the Supplier). We are using a 6x36 construction Right Hand Lay Wire Rope (Minimum Breaking Strenth 372KN) and is tightly wound on the drum.
Can any one provide any insights as to what might be causing this abrupt failure?

IRstuff · Apr 20, 2016

A picture of the damage would probably be useful

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berkshire · Apr 20, 2016

Have you checked the lead in angles of any sheaves in the rig to ensure the lines are going fair onto the sheaves?
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chicopee · Apr 20, 2016

Is the damage throughout the whole length of the cable or is it just the sides of the cable in contact with the drum flanges which one side appear fretted? Have you checked the condition of all the sheaves to make sure that they are not cracked, fretted, worn out.
Get a maintenance manual on this crane to be sure that all sheaves and drum have the proper diameters.

frzing8585 · Apr 22, 2016

The cuts on the Wire rope are found throughout the rope winding on the Second layer of the Drum at distances varying from 700mm-1400mm between successive cuts. The boom starts lifting when the wire rope gets wound on to this layer on the drum. Most of these cuts are observed at Crossover points on the rope.
We had inspected the Sheaves and they were found to be alright(No signs of damage found on the sheaves as such).

(Image with marking of position of the cuts on the wire rope)

BigHarvey · Apr 22, 2016

Check manufacturer's specs, it seems to me you should have a LH and not a RH cable.

frzing8585 · Apr 23, 2016

The spec's mentions RHO Wire Rope.
Can I know What factors would determine the Lay orientation of the Rope?
We were also discussing on the Fleeting Angle of the Wire Rope onto the Drumfrom the pulley amongst our team. The supplier mentions that the Fleet angle incorporated here 0.56 Degree which is according to him in the acceptable range(0.5 Degrees to 2.5 Degrees). Would increasing the Fleeting angle to say 0.8-0.9 Degree reduce the stresses during Overlapping of Wire Rope at Crossover points?

Many Thanks for your valuable inputs.

chicopee · Apr 23, 2016

Increasing the fleet angle would increase contact stresses between rows of wound rope. I don't think that is your problem though. There is a chart that details causes of rope damage which you can get from crane books in order to pinpoint the cause of your problem.
Have you discussed the problem with the crane manufacturer and the wire rope supplier? Is this crane used strictly for lifting and not for example dragging buckets? Any side loading taking place?

BUGGAR · Apr 23, 2016

You are using a regular lay. Lang lay will wind around a tighter sheave but is more sensitive to a
too-small radius. What does wire rope manufacturer say?

chicopee · May 4, 2016

Also the replacement with non rotational wire rope should be explored.

Tmoose · May 7, 2016

Got a sample of the old cable?
How did it last?

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