NCCCO Load Charts and Capacity Calculations 3

Question 1

A crane has a load chart capacity of 55,000 lbs at a 25-foot radius. The actual load weighs 50,000 lbs and the rigging weighs 1,500 lbs. What percentage of rated capacity is this lift?

Accepted Answer

93.6%

Answer

Total suspended weight = 50,000 + 1,500 = 51,500 lbs. Percentage of capacity = (51,500 / 55,000) × 100 = 93.6%.

Question 2

What is the effect on rated crane capacity when wind speed increases above the manufacturer's specified limit?

Accepted Answer

Operations must stop; the manufacturer's wind speed limit defines the maximum condition under which the load chart is valid

Answer

Load chart rated capacities are valid only within the wind speed limits specified by the manufacturer. When wind exceeds those limits, the load chart no longer applies and crane operations must cease.

Question 3

When using a load chart for a crane with a jib (fixed or luffing), what additional variable must the operator consider beyond boom length and radius?

Accepted Answer

The jib angle or jib offset relative to the main boom, as jib charts have separate entries for each jib configuration

Answer

When a crane is equipped with a jib, the load chart includes separate tables for different jib angles or offsets, and the operator must use the table corresponding to the actual jib angle being used.

Question 4

What does 'interpolation' mean in the context of reading crane load charts, and is it generally permitted?

Accepted Answer

Interpolation means estimating a capacity between two listed values; some manufacturers permit this while others do not

Answer

Interpolation is the mathematical process of estimating a value between two known chart values. Whether interpolation is permitted depends on the crane manufacturer's specific instructions in the load chart documentation.

Question 5

When does a lift require a formal, written critical lift plan under ASME P30.1?

Accepted Answer

Lifts exceeding 75% of the crane's rated capacity, multiple crane lifts, or lifts determined to be critical by a qualified person

Answer

ASME P30.1 defines critical lifts as those exceeding 75% of the crane's rated capacity, multiple crane lifts, or those where a qualified person determines a written plan is required due to unusual risks.

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 3