NCCCO Load Charts and Capacity Calculations

Question 1

When reading a mobile crane load chart, what two primary variables determine the rated lifting capacity?

Accepted Answer

Working radius and boom length/angle

Answer

Load charts are organized by working radius (horizontal distance from center of rotation to the load) and boom length or angle configuration. These two variables intersect to give the maximum rated load.

Question 2

A mobile crane load chart shows a capacity of 40,000 lb at a 30-foot radius. The rigger plans to lift a 38,000-lb load plus 800 lb of rigging hardware. What is the total suspended load?

Accepted Answer

38,800 lb — rigging hardware weight must be added to the load weight

Answer

Total suspended load includes the load weight plus all below-the-hook rigging hardware (shackles, slings, spreader bars, hooks). Here: 38,000 + 800 = 38,800 lb total.

Question 3

What does the deduction column on some load charts represent?

Accepted Answer

The weight of the hook block and ball that must be subtracted from the rated capacity to get net load capacity

Answer

The deduction column lists the weight of the crane's own hook block/ball assembly. This weight counts as part of the lifted load and must be deducted from the rated capacity to determine the actual net weight you can attach to the hook.

Question 4

A crane is rated for 20 tons at a 40-foot radius on fully extended outriggers. The operator is setting up on a slope of 2%. What is required before using the rated capacities?

Accepted Answer

Re-level the crane to within manufacturer tolerances — off-level operation voids the load chart

Answer

Load charts are developed for level operation (within manufacturer-specified tolerance, typically ±1%). Operating off-level shifts the center of gravity and reduces tipping stability — the crane must be leveled before using rated capacities.

Question 5

Which of the following correctly describes 'working radius' as used in crane load charts?

Accepted Answer

Horizontal distance from the center of the crane's rotation to the center of the suspended load

Answer

Working radius is the horizontal distance — not the boom length — from the center of rotation (turntable center pin) to the plumb line of the suspended load. It determines the overturning moment.

NCCCO (National Commission for the Certification of Crane Operators) Practice Test

NCCCO (National Commission for the Certification of Crane Operators) Practice Test

NCCCO Load Charts and Capacity Calculations