Wire Rope Basics
Wire rope holds up the load on cranes, hoists and winches, and is used for slings and guys. It’s strong, but it wears out from bending, crushing, corrosion and abuse. The damage often starts small and hidden, which is why it must be inspected every shift.
- Construction
- Cranes
- Rigging
How it’s built
- Wires are twisted into strands.
- Strands are twisted around a core: a fiber core (more flexible) or an independent wire rope core, IWRC (stronger and more crush-resistant).
- Lay is the direction and pattern of the twist. One “rope lay” is the length along the rope in which one strand makes a full turn. Inspection criteria are often counted per lay.
- Common classes like 6x19 and 6x37 mean 6 strands with about 19 or 37 wires each. More wires are more flexible but less resistant to abrasion.
- Rotation-resistant rope is built to resist spinning under load but is easier to damage and has stricter removal criteria.
Use only the rope type, size and grade the crane or hoist manufacturer specifies.
Inspections
- Each shift: a competent person visually checks the rope in use for obvious damage (OSHA 1926.1413).
- Monthly: a documented inspection like the shift check.
- Annually: a thorough inspection by a qualified person, including the full length of rope as far as practical.
- Wear leather gloves. Broken wires (“fishhooks” or “meat hooks”) cut hands. Never run your bare hand along a rope.
Remove from service when you find
- Broken wires: for running ropes, OSHA’s criteria include 6 randomly distributed broken wires in one rope lay, or 3 broken wires in one strand in one lay (stricter limits apply to rotation-resistant rope)
- Kinks, crushing, flattening or bends
- Birdcaging: strands that have opened up like a cage
- Core protruding between the strands
- Heat damage, arc strikes or electrical contact
- Heavy corrosion or pitting
- A diameter reduced more than about 5% from its nominal size
- Damaged or improperly installed end fittings
Some conditions call for removal right away; others allow continued use with closer monitoring if a qualified person approves. When in doubt, take it out of service and ask. See Crane Inspections.
Caring for wire rope
- Spool rope evenly on the drum, with the right tension, so it doesn’t crush itself.
- Keep at least two full wraps on the drum at all times (or what the manufacturer requires).
- Use sheaves of the right size with grooves in good shape. Small or worn sheaves wear rope fast.
- Lubricate as the manufacturer recommends.
- Unreel new rope straight off the reel, not off the side, to avoid kinks.
- Don’t drag rope over sharp edges or through dirt.
- Don’t shock-load it or use it as a ground for welding.
- Don’t try to straighten a kink and keep using the rope.
Wire rope slings
Wire rope slings follow similar rules, under OSHA 1910.184 and ASME B30.9, and need a legible tag showing the rated load. See Sling Inspection.
Standards & references
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