4.2 Wire Rope & Rigging Hardware
Key Takeaways
- Wire rope is built from wires laid into strands and strands laid around a core; running rope is removed for broken wires, corrosion, kinks, core protrusion, and diameter loss per ASME B30.5
- Sling tension rises sharply as the angle from horizontal decreases; a low sling angle can multiply leg tension far above the share of the load weight
- Hooks, shackles, and blocks must be rated, identifiable, and inspected; shackle pins must be the correct matched pin, never substituted with a bolt
- Increasing parts of line through the load block multiplies lifting capacity up to the hoist and rope limits but slows hook speed
- Reeving is the path of wire rope through the boom-tip and load-block sheaves; incorrect reeving or two-blocking can fail the rope or destroy the block
Rigging is not a separate trade on the NCCCO core exam — it is treated as part of safe crane operation. Technical Knowledge questions expect you to inspect wire rope, choose and angle slings correctly, identify hardware, and understand how the rope is run through the blocks. A rigging mistake is one of the most common causes of dropped loads, so this material is heavily tested.
Wire Rope Construction
Wire rope is built in three layers: individual wires are laid into strands, and the strands are laid helically around a core. The core can be a fiber core (FC) or an independent wire rope core (IWRC), which adds strength and crush resistance. A common description like 6 x 19 means 6 strands of about 19 wires each.
Key terms the exam uses:
- Lay: the direction the wires and strands are twisted (for example, right regular lay).
- Running rope: rope that bends over sheaves and spools on the drum (the hoist rope).
- Standing rope: rope that is fixed, such as boom pendants or guy lines.
Wire Rope Inspection and Removal
Wire rope must be inspected before use and removed from service when it is unsafe. The American Society of Mechanical Engineers standard ASME B30.5 (mobile and locomotive cranes) drives the removal criteria the exam expects. Remove running rope from service for conditions such as:
| Condition | Typical Removal Trigger |
|---|---|
| Broken wires | Several randomly distributed broken wires in one rope lay, or broken wires concentrated in one strand |
| Wear / diameter loss | Loss of original diameter from outside-wire wear beyond the allowable amount |
| Corrosion | Pitting or corroded, broken wires |
| Kinks / crushing | Kinking, crushing, birdcaging, or other distortion of the rope structure |
| Heat damage | Evidence of heat damage from any source |
| Core protrusion | Core pushing out between strands (a sign of overload or shock load) |
The exact broken-wire count comes from the manufacturer and the standard; for the exam, know the categories, that any kink, birdcage, or core protrusion is cause for removal, and that a damaged rope is replaced, never spliced back into hoisting service.
Slings and Sling Angle
Sling types include wire rope slings, alloy chain slings, and synthetic web/round slings. Each has a rated capacity that depends on the hitch (vertical, choker, or basket) and, in a multi-leg lift, on the sling angle.
The single most-tested rigging concept is sling angle. As the angle measured from horizontal decreases, the tension in each sling leg increases sharply even though the load weight has not changed.
| Sling Angle from Horizontal | Approx. Tension Multiplier (per leg vs. its share) |
|---|---|
| 90 degrees (vertical) | 1.00 |
| 60 degrees | about 1.15 |
| 45 degrees | about 1.41 |
| 30 degrees | about 2.00 |
A 30-degree angle roughly doubles the tension. This is why riggers avoid low sling angles and why a sling rated for the load straight down can still fail at a shallow angle.
Hooks, Shackles, and Blocks
- Hooks: must have a legible rated capacity and identification. Remove a hook for cracks, a throat opening that has stretched beyond the allowable percentage, or twist/bend. A safety latch keeps slings from jumping out but is not a load-bearing part.
- Shackles: anchor (bow) and chain (D) types. The pin must be the correct matched pin for that shackle body — never substitute a bolt or mismatched pin, and never side-load a shackle beyond its reduced rating.
- Load block / hook block: the assembly of sheaves, side plates, and the hook that the wire rope reeves through. It must be rated for the load and free to rotate.
Parts of Line and Reeving
Parts of line is the number of rope parts supporting the load block. Each added part shares the load, so total lifting capacity is roughly the single-line pull multiplied by the number of parts — until limited by the chart, rope, or hoist. More parts means more capacity but slower hook speed.
Reeving is the path the wire rope takes through the boom-tip sheaves and the load-block sheaves. Reeving must be correct and even; a critical hazard is two-blocking, where the load block runs up into the boom tip. Two-blocking can snap the rope and drop the load, which is why cranes use an anti-two-block (ATB) device.
A four-leg bridle is rigged so each sling leg is at 30 degrees from horizontal. Compared with a vertical (90-degree) lift, the tension in each loaded sling leg is approximately:
During inspection you find the wire rope core protruding between the outer strands. The correct action is to:
Increasing the parts of line through the load block from two parts to four parts will:
Which practice involving a shackle is acceptable?