NCCCO Load Charts & Capacity Calculations 2 — Questions and Answers
Question 1: What information is needed to use a crane's load chart correctly?
- Only the load weight
- Boom length, operating radius, crane configuration, and ground conditions (Correct answer)
- The color of the load
- The time of day
Correct answer: Boom length, operating radius, crane configuration, and ground conditions
To find rated capacity on a load chart, you need: boom length/configuration, operating radius (distance from center of rotation to load), quadrant of operation, and whether outriggers are deployed.
Question 2: What is 'operating radius' and how is it measured?
- The distance from the crane to the nearest building
- The horizontal distance from the center of rotation to the center of the load (Correct answer)
- The height of the boom
- The length of the wire rope
Correct answer: The horizontal distance from the center of rotation to the center of the load
Operating radius is measured horizontally from the crane's center of rotation (center pin) to the center of the hook/load. As radius increases, lifting capacity decreases.
Question 3: As the operating radius increases, what happens to the crane's rated capacity?
- It increases proportionally
- It decreases — the farther the load is from the crane, the less it can lift (Correct answer)
- It stays the same regardless of radius
- It first increases then decreases
Correct answer: It decreases — the farther the load is from the crane, the less it can lift
Capacity decreases as radius increases because the tipping moment (load weight × radius) increases. The crane can lift the most weight closest to its center of rotation.
Question 4: What must be subtracted from the load chart capacity to determine the actual weight you can lift?
- Nothing — the chart shows net capacity
- The weight of the hook block, rigging (slings, shackles), and any headache ball (Correct answer)
- Only the hook block weight
- Only the wire rope weight
Correct answer: The weight of the hook block, rigging (slings, shackles), and any headache ball
Load chart capacity includes everything hanging from the boom tip. You must subtract the weight of hook block, headache ball, wire rope, and all rigging to find the available capacity for the actual load.
Question 5: A crane has a rated capacity of 50 tons at 30 feet radius. The rigging weighs 2 tons. What is the maximum load that can be lifted?
- 50 tons
- 48 tons (Correct answer)
- 52 tons
- 30 tons
Correct answer: 48 tons
Maximum net load = rated capacity minus rigging weight = 50 - 2 = 48 tons. The rigging is part of the total weight the crane must support.
Question 6: Why do load charts show different capacities for different quadrants (over front, over side, over rear)?
- Different quadrants have different paint colors
- The crane's stability varies depending on which direction it's facing due to counterweight position and outrigger configuration (Correct answer)
- It's an error in the load chart
- Different quadrants use different hoisting mechanisms
Correct answer: The crane's stability varies depending on which direction it's facing due to counterweight position and outrigger configuration
Crane stability varies by quadrant because of how the counterweight, outrigger spread, and crawler positioning affect the tipping line in each direction.
NCCCO Load Charts & Capacity Calculations 2
What information is needed to use a crane's load chart correctly?