Tiredness Kills - Fatigue Breaks in Wire Rope

What are fatigue breaks and how are they identified?

The individual wires in wire rope have a fatigue life limit, which when exceeded, will cause them to break.   Typical external fatigue breaks are visible on the outside of the wire rope where the crown of the strand is in contact with the sheaves, drums and other contact points on the crane. They will predominate in the main working part of the rope.

A fatigue break will show as a flat ended break in the wire (see the below image). The break will start as a hairline crack and will eventually tear away.   A single fatigue crown wire break is generally not serious unless it is near the termination. So what are the limits and how do we know when to reject?

Typical fatigue broken wires shown on the strand crown of a wire rope.

Discard Criteria standards

The discard criteria specified in this presentation are in line with ISO 4309:2010 (2017 edition now available) It is the responsibility of the Competent Person to determine what standards apply to your industry, either International, National,   Industrial or Company.

Count the number of visible wire breaks occurring randomly in sections of rope which run through one or more steel

sheaves and spool on and off the drum when single-layer spooling or occurring at sections   of rope   which are coincident   with cross-over zones when multi-layer spooling over lengths of 6 or 30 diameters.

Discard Criteria