NCCCO Load Charts & Capacity Calculations 5 — Questions and Answers
Question 1: What does 'tipping capacity' mean in the context of crane load charts?
- The maximum load before the crane tips over (Correct answer)
- The minimum load required to maintain stability
- The load at which the crane is designed to operate at full efficiency
- The capacity reduced by 85% for the rated load chart
Correct answer: The maximum load before the crane tips over
Tipping capacity is the theoretical load at which the crane would begin to tip; rated capacities are a percentage of this value.
Question 2: A crawler crane's load chart has separate columns for 'on crawlers' and 'with carbody blocked.' When would you use the blocked carbody column?
- When the crane is traveling with a load
- When the crane's carbody is supported by cribbing or blocking to increase stability (Correct answer)
- When operating at maximum boom length
- When the load exceeds 50% of chart capacity
Correct answer: When the crane's carbody is supported by cribbing or blocking to increase stability
Blocking the carbody with cribbing distributes the load to a wider area, increasing stability and allowing higher rated capacities.
Question 3: How does wind affect crane load chart capacities during a lift?
- Wind has no effect if the load is below 50% of rated capacity
- Wind creates additional side loading that reduces effective lifting capacity (Correct answer)
- Wind only matters for lifts above 100 ft height
- Wind increases stability by counteracting the load weight
Correct answer: Wind creates additional side loading that reduces effective lifting capacity
Wind applies lateral forces to the load, boom, and crane, creating additional stresses not reflected in standard load chart capacities.
Question 4: On a lattice boom crane load chart, why are capacities listed for specific boom lengths rather than a continuous range?
- Lattice booms can only be assembled in fixed length increments (Correct answer)
- Regulations require only specific boom lengths to be tested
- Load charts are too complex to calculate for all possible lengths
- Only certain boom lengths are approved by OSHA
Correct answer: Lattice booms can only be assembled in fixed length increments
Lattice boom sections come in fixed lengths and can only be assembled in specific increments, so load charts reflect those discrete configurations.
Question 5: A load chart shows a maximum radius of 60 ft for a given configuration. The planned lift requires a 65 ft radius. What must the operator do?
- Reduce the load by 10% to account for the extra 5 ft
- The lift cannot be performed at that radius in that configuration (Correct answer)
- Contact the load chart manufacturer to estimate the 65 ft capacity
- Increase the boom length and recalculate using the same chart
Correct answer: The lift cannot be performed at that radius in that configuration
Operating beyond the maximum radius listed on the load chart is prohibited; the operator must reconfigure the crane or change the lift plan.
Question 6: What does the term 'rated capacity' mean under ASME B30.5?
- The absolute maximum load the crane can physically lift
- The load capacity assigned by the manufacturer for specific configurations, typically 75-85% of tipping load (Correct answer)
- The capacity tested and certified by a third-party inspector
- The load limit set by OSHA for all crane types
Correct answer: The load capacity assigned by the manufacturer for specific configurations, typically 75-85% of tipping load
Under ASME B30.5, rated capacity is the manufacturer-designated maximum load for specific crane configurations, which must be at or below 75-85% of tipping capacity.
Question 7: When a load chart shows a jib (fly) attached to the main boom, how is the working radius measured?
- From the center of rotation to the tip of the main boom
- From the center of rotation to the centerline of the suspended load (Correct answer)
- From the center of the hook block to the centerline of the crane
- From the tip of the jib to the nearest outrigger pad
Correct answer: From the center of rotation to the centerline of the suspended load
Working radius is always measured horizontally from the crane's center of rotation to the centerline of the suspended load, regardless of boom/jib configuration.
NCCCO Load Charts & Capacity Calculations 5
What does 'tipping capacity' mean in the context of crane load charts?