Load Charts & Capacity Calculations Flashcards
6 cards from real NCCCO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Load Charts & Capacity Calculations flashcards as text
What is a 'tipping line' in crane capacity calculations?
Answer: The axis around which the crane would tip if overloaded, defined by the crane's support points
The tipping line (or fulcrum line) connects the crane's support points (outrigger pads or crawler edges) on the side toward the load. The crane tips when the load moment exceeds the counterweight moment about this line.
How does boom angle affect the operating radius?
Answer: Higher boom angle decreases radius (load moves closer to the crane center)
Raising the boom angle brings the load closer to the crane's center of rotation (shorter radius), which increases capacity. Lowering the boom angle moves the load farther away (longer radius), reducing capacity.
What does it mean to operate at '75% of rated capacity'?
Answer: The crane is lifting 75% of the maximum allowed load, leaving a 25% safety margin
Operating at 75% of rated capacity means the load is three-quarters of the maximum allowed. Many companies mandate operating at 75% or less for routine lifts, reserving the full capacity for planned critical lifts.
A lift plan calls for a 40-foot radius. During the lift, the radius increases to 45 feet due to boom deflection. What is the danger?
Answer: The crane may now exceed its rated capacity at the greater radius, risking tip-over
At 45 feet, the crane's rated capacity may be significantly less than at 40 feet. If the load was near capacity at 40 feet, the increased radius from boom deflection could put the crane over its limit.
What is 'structural capacity' versus 'stability capacity' on a load chart?
Answer: Structural = max load before boom/components break; Stability = max load before the crane tips over. The chart shows the lower value.
Load charts show the lesser of two limits: structural capacity (component strength) and stability capacity (tipping resistance). At short radius, structural usually governs; at long radius, stability governs.
How is the weight of an unknown load estimated on a job site?
Answer: Using shipping documents, manufacturer specs, volume calculations, or a crane scale — never guess
Load weight must be determined using reliable sources: shipping documents, manufacturer specifications, engineering calculations, or weighing devices. Estimation by sight is never acceptable for crane lifts.