NCCCO Sling Types and Load Distribution 5 — Questions and Answers
Question 1: What is the primary reason sling angles below 30 degrees from horizontal are generally prohibited?
- The sling becomes too short to attach to the hook
- Tension in sling legs exceeds two times the load weight, drastically increasing failure risk (Correct answer)
- The load swings outward beyond the crane's load chart
- Hook latches cannot engage at shallow angles
Correct answer: Tension in sling legs exceeds two times the load weight, drastically increasing failure risk
At angles below 30 degrees from horizontal, the tension multiplier exceeds 2.0, meaning each sling leg must support more than the total load weight, risking sling failure.
Question 2: A polyester web sling offers an advantage over nylon in which specific environment?
- Alkaline (caustic) environments
- Acidic environments (Correct answer)
- High-temperature environments above 194°F
- Areas with heavy UV exposure
Correct answer: Acidic environments
Polyester is more resistant to acids than nylon, making it preferable in mild acidic environments, though both types have chemical exposure limitations.
Question 3: When a load's center of gravity is higher than the attachment points of a multi-leg bridle sling, the result is:
- Improved stability and lower sling tension
- An unstable lift that could cause the load to tip over (Correct answer)
- Reduced sling angle stress
- No effect on lift stability
Correct answer: An unstable lift that could cause the load to tip over
If the COG is above the attachment points, the load is top-heavy and will be unstable, risking a tip-over once lifted free of the ground.
Question 4: Which type of sling provides the best resistance to abrasion during dragging operations?
- Nylon web slings
- Polyester roundslings
- Wire rope slings (Correct answer)
- Flat synthetic slings
Correct answer: Wire rope slings
Wire rope slings have superior abrasion resistance compared to synthetic slings, making them more suitable where contact with rough surfaces is expected.
Question 5: An alloy chain sling must be proof-tested to what load before being placed into service?
- The rated working load limit
- 1.5 times the rated working load limit (Correct answer)
- 2 times the rated working load limit
- 3 times the rated working load limit
Correct answer: 1.5 times the rated working load limit
New alloy chain slings are proof-tested to 1.5 times their rated working load limit prior to being placed into service, per ASME B30.9 requirements.
Question 6: When calculating the load per sling leg in a two-leg bridle, if the total load is 8,000 lbs and the sling angle is 45 degrees from horizontal, what is the approximate tension per leg?
- 4,000 lbs
- 5,660 lbs (Correct answer)
- 6,930 lbs
- 8,000 lbs
Correct answer: 5,660 lbs
At 45 degrees, the tension factor is approximately 1.414; each leg carries (8,000 / 2) × 1.414 ≈ 5,656 lbs, rounded to 5,660 lbs.
Question 7: What action should be taken if a synthetic sling's identification tag is missing or illegible?
- Estimate capacity based on sling width and color
- Remove the sling from service until properly identified and tagged (Correct answer)
- Use the sling only for loads under 1,000 lbs
- Attach a new tag with the same information as another similar sling
Correct answer: Remove the sling from service until properly identified and tagged
Without legible identification, the rated capacity cannot be verified, so the sling must be removed from service per ASME B30.9.
NCCCO Sling Types and Load Distribution 5
What is the primary reason sling angles below 30 degrees from horizontal are generally prohibited?