Wire rope discard criteria under ISO 4309, in plain English

ISO 4309 is the standard behind every rope inspection on a crane. It is not a pass or fail switch. It is a set of degradation modes, each with its own limit, and a rope goes off the drum when any single one is reached.

Broken wires

The count depends on rope construction and whether it runs on steel or synthetic sheaves, so a single number quoted across a whole yard is a warning sign in itself. The examiner counts visible breaks over a reference length of six rope diameters and again over thirty. Breaks clustered in one lay are worse than the same number spread over a length, and breaks at a termination usually mean the rope is finished regardless of the count.

Diameter reduction

Measure across the crowns of opposing strands with the correct caliper, at several points along the working length, and compare against the actual measured diameter of the new rope rather than the nominal size. A steady reduction points to core collapse, and core collapse is a discard condition even where the wire count looks acceptable.

Corrosion

External corrosion is visible and pitting is what matters, not surface rust. Internal corrosion is the one that ends ropes without warning, and the signs are a reduction in diameter with no obvious wear, or wires that have lost the tight nested feel when the rope is opened at a bend.

Deformation

Waviness, basket or lantern deformation, core protrusion, kinks, flattening and birdcaging. Any of these that reach the levels in the standard are immediate discard, and several of them mean the rope was damaged by handling rather than worn out in service.

What a good rope report contains

• Rope construction, diameter, grade and date fitted.
• The measured diameter of the new rope, recorded when it was fitted.
• Broken wire counts by reference length, with their positions.
• Diameter readings at defined points along the working length.
• The examiner's judgement on remaining service life, with a re-check date.

Sites that keep a rope file from the day the rope is fitted get years of useful trend data. Sites that only produce the last certificate are guessing every time.