INSPECTIONS:

Steel wire rope is subject to rapid deterioration through exposure to excessive heat, moisture. chemicals and a wide range of environmental factors in addition to certain harsh applications.

All ropes will eventually wear out and gradually lose nominal strength throughout their service of life, which necessitates periodical inspections.  A regular visual inspection of wire rope and equipment used in conjunction with it will reveal the following:

• The condition of the wire rope and its remaining service life;

• If rapid or accelerated wear is present, possible alternate constructions that could be recommended;

• Potential faults in equipment or rigging that could be discovered.

Inspections should be carried out by an experienced person who is familiar with the product, its application, and has learned through special training and/or practical experience what to look for.  The ability to judge the importance of any abnormal conditions and to maintain an accurate record of inspections is crucial.

Common Rope Failures:


This sample wire indicates that its failure was due to a load/stress that exceeded its working load capacity and ultimately its nominal strength.  The "Cup & Cone" appearance at the break reveals a necking down of the wire at the point of failure.

Clearly this sample wire is a distinct fatigue break, which is easily recognizable by square end perpendicular to the wire.

A wire rope that has been subjected to repeated bending over sheaves under normal loads.  This results in fatigue breaks in individual wires-these breaks are square and usually in the crown of the strands.

This wire rope sample shows what happens when wire rope is subjected to heavy loads while running over small sheaves.  Wire breaks in the valleys of the strands and some crown wire breaks are also visible.

This single strand was removed from a wire rope and clearly shows "strand nicking".  The cause of this nicking is a result of adjacent strands rubbing against one another.  While this is normal in the operation of wire rope, this condition can be accelerated by heavy loads, core deterioration or sheaves that may be worn, or too small. 

Samples of Wire Rope Wear and Abuse:


This birdcage was caused by a sudden release of tension while under load and the resulting rebounding action.  The individual wire and strands will not recover and this failure is cause for immediate removal from service.

Here is a sample of wire rope that has excessive internal wear, which can only be determined by an internal inspection while the rope is in a slack position.  This localized wear would likely be invisible during the ropes operation .

When a wire rope jumps a sheave, this type of a curled break quickly follows.

 

Diversified Chain and Rigging - Brooks and Area, Saskatchewan and Alberta