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CT Crane Operator study materials
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CT Crane Operator: Rigging, Slings, and Below-the-Hook Devices

CT Crane Operator · Work through your exam, one topic at a time.

All guide sections

Rigging, Slings, and Below-the-Hook Devices

What the exam tests

This domain tests whether you can select and inspect rigging for the load, calculate tension in angled slings, and recognize when a below-the-hook device changes the lift. Expect questions on working load limit (WLL), hitch types, sling angle, hardware, and inspection rejection criteria.

Core rules

  • WLL is the maximum load for a specific sling, hitch, and configuration. Do not use the nominal breaking strength as a working limit.
  • ASME B30.9 safety factors are commonly 5:1 for wire rope, synthetic web, and metal mesh slings, and 4:1 for alloy chain slings. The tag and manufacturer's data govern.
  • Hitch type changes capacity. A vertical hitch uses the full vertical WLL; a choker hitch reduces capacity because the sling is compressed around the load; a basket hitch can increase capacity only when both legs are loaded evenly and the hitch is properly seated.
  • Sling angle matters. As the angle from horizontal decreases, tension in each leg increases. For a two-leg bridle, tension per leg = load / (2 x sin of the angle to horizontal).
  • Protect slings from sharp edges, heat, chemicals, and abrasion. Do not shock-load, drag, or side-load slings.
  • Below-the-hook devices include spreader beams, lifting clamps, magnets, vacuum lifters, and pallet forks. They must be rated, marked, and inspected; the device weight is a deduction from crane capacity.

Worked example

A 4,000 lb load is lifted with a two-leg bridle. Each leg makes a 60-degree angle with horizontal. Tension per leg = 4,000 / (2 x sin 60) = 4,000 / 1.732 = 2,309 lb. If each sling has a vertical WLL of 2,000 lb, the bridle is overloaded even though the total load is only 4,000 lb. A larger sling, a lower included angle, or a spreader beam may be required. If a 250 lb spreader beam is added, the crane must also deduct that 250 lb from its net capacity.

Traps

  • Using the vertical WLL for a choker hitch.
  • Ignoring the sling angle and using only total load weight.
  • Assuming a basket hitch always doubles capacity.
  • Forgetting the weight of shackles, spreader beams, and clamps in the crane chart deductions.
  • Accepting a sling with a missing tag or damaged hardware because it 'looks strong'.