NCCER Crane Load Charts & Rigging Principles 5 — Questions and Answers
Question 1: During a tandem lift involving two cranes, who is responsible for ensuring the total lift does not exceed either crane's rated capacity?
- Only the larger crane's operator
- A qualified lift director or engineer who coordinates both crane capacities (Correct answer)
- The signal person assigned to the lift
- Each operator independently without coordination
Correct answer: A qualified lift director or engineer who coordinates both crane capacities
Tandem lifts require a qualified lift director or engineer to plan the operation, ensuring load distribution does not exceed either crane's rated capacity at its specific radius and configuration.
Question 2: What is the purpose of a 'load moment indicator' (LMI) on a crane?
- To measure the actual weight of the suspended load on a scale
- To calculate and display the ratio of the actual load moment to the crane's rated capacity and warn of overload (Correct answer)
- To automatically stop the hoist when the load exceeds capacity
- To record the maximum load lifted during a shift
Correct answer: To calculate and display the ratio of the actual load moment to the crane's rated capacity and warn of overload
An LMI monitors boom angle, radius, and load to calculate the current load moment and compare it to rated capacity, providing the operator with a percentage reading and overload warning.
Question 3: Wire rope with a visible kink should be:
- Straightened by hand and returned to service if no broken wires are visible
- Removed from service immediately (Correct answer)
- Lubricated and monitored for further damage
- Used for lighter lifts below 50% of its rated capacity
Correct answer: Removed from service immediately
A kinked wire rope has suffered permanent deformation that weakens its load-bearing capacity and must be removed from service regardless of visible broken wires.
Question 4: What is the effect of temperature extremes on synthetic sling capacity?
- Synthetic slings are unaffected by temperature
- High temperatures can reduce synthetic sling capacity, requiring derating per manufacturer guidelines (Correct answer)
- Cold temperatures increase synthetic sling capacity
- Only wire rope slings are affected by temperature
Correct answer: High temperatures can reduce synthetic sling capacity, requiring derating per manufacturer guidelines
High temperatures weaken synthetic fibers such as nylon and polyester, reducing working load limits; manufacturers provide derating tables for elevated temperature conditions.
Question 5: When calculating the sling angle factor (SAF) for a two-leg bridle, a sling angle of 30 degrees from horizontal results in an SAF of approximately:
- 1.0
- 0.87
- 0.50 (Correct answer)
- 2.0
Correct answer: 0.50
The sling angle factor = sin(θ), and sin(30°) = 0.5, meaning each sling leg must carry twice what it would carry if rigged vertically, doubling the tension.
Question 6: In a crane load chart, the footnote 'capacities do not exceed 85% of tipping' means:
- The crane will tip at 85% of the listed capacity
- The listed capacities have already been limited to 85% of the theoretical tipping load to provide a safety margin (Correct answer)
- Operators must reduce all lifts to 85% of the chart value
- The chart is only valid when 85% of the counterweight is installed
Correct answer: The listed capacities have already been limited to 85% of the theoretical tipping load to provide a safety margin
ASME B30.5 requires that mobile crane rated capacities on outriggers not exceed 85% of the theoretical tipping load, so the derating is already factored into the published chart.
Question 7: A rigger notices the load chart shows 'NA' (not applicable or not available) for a particular boom length and radius combination. This means:
- The crane can lift any load at that configuration
- No safe rated capacity exists for that configuration and the lift must not be made (Correct answer)
- The operator should estimate based on nearby chart values
- The crane manufacturer must be called for a special rating
Correct answer: No safe rated capacity exists for that configuration and the lift must not be made
An 'NA' entry indicates the manufacturer has determined no safe rated capacity exists for that boom length and radius combination, and the lift must not be attempted.
NCCER Crane Load Charts & Rigging Principles 5
During a tandem lift involving two cranes, who is responsible for ensuring the total lift does not exceed either crane's rated capacity?