NCCER Crane Load Charts & Rigging Principles 3

Question 1

What is the significance of the 'tipping line' in crane stability calculations?

Accepted Answer

The fulcrum axis over which a crane would rotate if it tipped

Answer

The tipping line is the axis (typically the outer edge of the outriggers or rear axle) over which the crane would rotate if it were overloaded and began to tip.

Question 2

Wire rope used for rigging should be removed from service if it has how many randomly distributed broken wires in one rope lay?

Accepted Answer

6 or more

Answer

ASME B30.9 specifies that wire rope slings with 6 or more randomly distributed broken wires in one rope lay must be removed from service.

Question 3

What effect does a choker hitch have on a sling's rated capacity compared to a vertical hitch?

Accepted Answer

Reduces capacity to approximately 75–80% of vertical rating

Answer

A choker hitch reduces a sling's working load limit to approximately 75–80% of its vertical hitch rating because of the bend and friction at the choke point.

Question 4

In crane load charts, 'structural' rated capacity is limited by:

Accepted Answer

The strength of the crane's boom, structure, and components

Answer

Structural capacity is the maximum load the crane's structural components—boom, luffing mechanism, pins—can handle before failure, independent of tipping.

Question 5

When rigging a load with a four-leg bridle sling, ASME standards assume how many legs are considered load-bearing for rating purposes?

Accepted Answer

Three legs, to account for the possibility that one leg may not be taut

Answer

ASME B30.9 conservatively assumes only three of four legs share the load, because minor load imbalances can result in one leg carrying little to no tension.

(NCCER Crane) National Center for Construction Education and Research Crane Certification Practice Test

(NCCER Crane) National Center for Construction Education and Research Crane Certification Practice Test

NCCER Crane Load Charts & Rigging Principles 3