NCCCO Load Charts and Capacity Calculations 4

Question 1

When using a load chart with a luffing jib attachment, what additional deduction must be applied to the main boom capacity?

Accepted Answer

The weight of the jib and all associated rigging must be subtracted from the rated capacity

Answer

The weight of the luffing jib assembly, including pins, rigging, and the jib hook block, must be subtracted from the main boom's rated capacity because the crane must support this weight before lifting any payload.

Question 2

A crane's load chart shows a capacity of 40,000 lbs at a 50-foot radius. If the total rigging weight is 800 lbs and the hook block weighs 600 lbs, what is the maximum net payload that can be lifted?

Accepted Answer

38,600 lbs

Answer

The net payload equals the rated capacity minus all weight below the hook: 40,000 − 800 − 600 = 38,600 lbs.

Question 3

On a telescoping boom crane load chart, why do capacities typically decrease as boom length increases at the same radius?

Accepted Answer

Longer booms increase structural stress and reduce stability, lowering the rated capacity

Answer

Longer boom sections increase bending moment and reduce structural integrity margins, and the boom's own weight further reduces net lifting capacity at any given radius.

Question 4

A crawler crane load chart lists two sets of capacities: 'over front' and 'over side.' Which is typically greater and why?

Accepted Answer

Over front, because the carbody and tracks provide greater tipping resistance in the longitudinal direction

Answer

Crawler cranes have greater stability lifting over the front due to the longer longitudinal distance between the tipping fulcrum and the crane's center of gravity.

Question 5

What does the term 'structural capacity' mean on a load chart as opposed to 'stability capacity'?

Accepted Answer

Structural capacity is limited by the strength of crane components, while stability capacity is limited by the crane's resistance to tipping

Answer

At short radii, cranes are often structurally limited (component strength governs), while at longer radii, stability (tipping resistance) typically becomes the governing factor.

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 4