NCCCO Rigging Techniques & Equipment Inspection 4 — Questions and Answers
Question 1: When inspecting a wire rope sling, which condition requires immediate removal from service?
- Minor surface rust that wipes off
- Six randomly distributed broken wires in one rope lay (Correct answer)
- Slight kinking that has been straightened
- A heat-shrink tag that is partially peeled
Correct answer: Six randomly distributed broken wires in one rope lay
ASME B30.9 requires removing a wire rope sling from service if six or more randomly distributed broken wires are found in one rope lay.
Question 2: What is the primary purpose of a shackle's safety pin or bolt?
- To increase the shackle's working load limit
- To prevent the pin from unscrewing under load (Correct answer)
- To allow the shackle to rotate freely
- To color-code the load rating
Correct answer: To prevent the pin from unscrewing under load
The safety pin or cotter pin on a shackle prevents the screw pin from backing out due to vibration or load cycling during a lift.
Question 3: A choker hitch reduces the rated capacity of a synthetic web sling to approximately what percentage of its straight-basket capacity?
- 100%
- 87%
- 75% (Correct answer)
- 50%
Correct answer: 75%
A choker hitch applied to a synthetic web sling reduces its rated capacity to approximately 75% of the straight-basket (vertical) capacity.
Question 4: During pre-use inspection of a chain sling, a rigger finds a link that is stretched and narrowed. What action should be taken?
- Continue using the sling if stretch is less than 5%
- Mark the link with a tag and monitor during the lift
- Remove the sling from service immediately (Correct answer)
- Apply penetrating oil and re-inspect after 30 minutes
Correct answer: Remove the sling from service immediately
A stretched or elongated link indicates overloading or shock loading; the sling must be removed from service and destroyed or repaired by a qualified person.
Question 5: What does the term 'D/d ratio' refer to in rigging?
- The ratio of dead load to dynamic load
- The ratio of the diameter of curvature to the wire rope diameter (Correct answer)
- The ratio of design factor to working load
- The ratio of drum wraps to rope diameter
Correct answer: The ratio of the diameter of curvature to the wire rope diameter
The D/d ratio compares the diameter of the curve a wire rope bends around (such as a hook or sheave) to the rope's own diameter, directly affecting rope service life.
Question 6: Which type of rigging hardware is specifically designed to allow a load to rotate freely without untwisting the hoist line?
- Swivel hook (Correct answer)
- Screw pin shackle
- Eye bolt
- Turnbuckle
Correct answer: Swivel hook
A swivel hook contains a bearing that allows the load attachment point to rotate freely, preventing torque from being transferred to the hoist rope.
Question 7: When using a bridle sling with four legs, the load is typically distributed among how many legs for rating purposes?
- All four legs equally
- Three legs (Correct answer)
- Two legs
- One leg
Correct answer: Three legs
For load distribution calculations, a four-leg bridle sling is rated assuming only three legs share the load because perfect load equalization across four legs cannot be guaranteed.
NCCCO Rigging Techniques & Equipment Inspection 4
When inspecting a wire rope sling, which condition requires immediate removal from service?