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

Hoist line speed and rope diameter

Answer

Counterweight weight and outrigger pad size

Answer

Engine horsepower and hydraulic pressure

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

38,000 lb — rigging hardware is excluded from load chart calculations

Answer

40,800 lb — the chart capacity must also be included

Answer

37,200 lb — only net load weight without any hardware

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 amount by which boom length reduces ground bearing pressure

Answer

A safety margin already built into the published capacities

Answer

The minimum counterweight required for each configuration

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

Apply a 2% derating factor to all load chart values

Answer

Proceed normally as 2% slope is within OSHA's acceptable range

Answer

Extend outriggers on the downhill side fully and use half capacity on the uphill side

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

The length of the boom from pivot pin to tip sheave

Answer

The maximum reach of the boom measured along its centerline

Answer

Vertical distance from ground level to the hook at maximum height

Question 6

A crane load chart note states 'Capacities are based on structural strength and do not exceed 75% of tipping load.' What does this note indicate?

Accepted Answer

The published capacities already include the ASME-required stability derating, so no further reduction is needed for normal lifts

Answer

The operator must manually reduce all chart values by an additional 25%

Answer

These capacities apply only to static lifts; dynamic lifts require a 50% reduction

Answer

The crane is rated for lattice boom only and not hydraulic boom configurations