NCCCO - National Commission for the Certification of Crane Operators Sling Types and Load Distribution 1

Question 1

A two-leg bridle sling is used to lift a 10,000 lb load, with each sling leg inclined 45° from vertical. What is the approximate tension in each leg?

Accepted Answer

7,071 lb — the incline increases tension by a factor of 1/cos(45°)

Answer

5,000 lb — each leg carries exactly half the total load

Answer

6,667 lb — the load is divided by the sine of the included angle

Answer

8,660 lb — tension is calculated using the tangent of the sling angle

Question 2

Under ASME B30.9, what is the rated load capacity of a wire rope sling used in a choker hitch expressed as a percentage of its vertical hitch capacity?

Accepted Answer

75% — the standard choker derating factor for wire rope slings

Answer

100% — the rated capacity is the same regardless of hitch type

Answer

80% — choker hitches reduce capacity due to the sharp bend

Answer

50% — wrapping the rope around the load halves its rated capacity

Question 3

When inspecting a synthetic web sling, which of the following conditions requires immediate removal from service?

Accepted Answer

Surface abrasion that has worn through 10% of the outer yarn bundles

Answer

A faded but still-legible capacity tag

Answer

Slight stiffening from routine exposure to low-humidity air

Answer

Minor oil contamination on the outer cover that has been wiped clean

Question 4

What does the designation 'Grade 80' (G80) stamped on an alloy steel chain sling indicate?

Accepted Answer

The minimum tensile strength class of the alloy steel, which governs the chain's rated capacity

Answer

The chain has a working load limit of 80 tons

Answer

The chain contains 80% iron and may not be used for overhead lifting

Answer

The chain passed an 80,000-cycle fatigue test

Question 5

A rigger uses a two-leg sling of equal leg lengths to lift a load whose center of gravity is offset significantly toward one end. What is the most likely result?

Accepted Answer

The leg over the heavier end carries a greater share of the load, potentially exceeding its rated capacity

Answer

Both legs share the load equally because the sling legs are the same length

Answer

The load automatically re-centers as the crane lifts, equalizing tension in both legs

Answer

The load will not move until the sling legs are adjusted to different lengths

Question 6

Which sling hitch configuration provides the highest rated load capacity for a single wire rope sling of a given size and length?

Accepted Answer

Basket hitch with the two legs vertical and parallel — the load is shared across two runs of rope

Answer

Vertical hitch — the rope is used in direct tension without any bends

Answer

Choker hitch — wrapping around the load adds friction that increases capacity

Answer

Inverted choker hitch — reversing the choke direction doubles rated load