Load Charts & Rigging Principles Flashcards

During a tandem lift involving two cranes, who is responsible for ensuring the total lift does not exceed either crane's rated capacity?

Answer: A qualified lift director or engineer who coordinates both crane capacities

Tandem lifts require a qualified lift director or engineer to plan the operation, ensuring load distribution does not exceed either crane's rated capacity at its specific radius and configuration.

What is the purpose of a 'load moment indicator' (LMI) on a crane?

Answer: To calculate and display the ratio of the actual load moment to the crane's rated capacity and warn of overload

An LMI monitors boom angle, radius, and load to calculate the current load moment and compare it to rated capacity, providing the operator with a percentage reading and overload warning.

Wire rope with a visible kink should be:

Answer: Removed from service immediately

A kinked wire rope has suffered permanent deformation that weakens its load-bearing capacity and must be removed from service regardless of visible broken wires.

What is the effect of temperature extremes on synthetic sling capacity?

Answer: High temperatures can reduce synthetic sling capacity, requiring derating per manufacturer guidelines

High temperatures weaken synthetic fibers such as nylon and polyester, reducing working load limits; manufacturers provide derating tables for elevated temperature conditions.

When calculating the sling angle factor (SAF) for a two-leg bridle, a sling angle of 30 degrees from horizontal results in an SAF of approximately:

Answer: 0.50

The sling angle factor = sin(θ), and sin(30°) = 0.5, meaning each sling leg must carry twice what it would carry if rigged vertically, doubling the tension.

In a crane load chart, the footnote 'capacities do not exceed 85% of tipping' means:

Answer: The listed capacities have already been limited to 85% of the theoretical tipping load to provide a safety margin

ASME B30.5 requires that mobile crane rated capacities on outriggers not exceed 85% of the theoretical tipping load, so the derating is already factored into the published chart.

A rigger notices the load chart shows 'NA' (not applicable or not available) for a particular boom length and radius combination. This means:

Answer: No safe rated capacity exists for that configuration and the lift must not be made

An 'NA' entry indicates the manufacturer has determined no safe rated capacity exists for that boom length and radius combination, and the lift must not be attempted.