RB Spreader Bars and Lifting Beams 3

Question 1

When lifting a long structural load such as a steel beam using a spreader bar, how many tag lines should be used?

Accepted Answer

Two tag lines — one at each end of the load

Answer

Two tag lines, one at each end of the load, allow the rigging crew to control both rotation and lateral swing of a long suspended load throughout the lift.

Question 2

During a test lift, the rigger observes that the spreader bar is not sitting level. What is the most likely cause?

Accepted Answer

Unequal sling leg lengths or the load's centre of gravity not directly below the pick point

Answer

An unlevel spreader bar most commonly results from unequal sling leg lengths or misalignment between the crane hook, the bar's pick point, and the load's centre of gravity.

Question 3

What is the generally accepted maximum angle that sling legs should form with the vertical when used with a spreader bar?

Accepted Answer

60 degrees from vertical

Answer

The generally accepted maximum sling angle is 60 degrees from vertical; beyond this, compressive forces on the spreader bar increase rapidly and sling load factors become unfavourable.

Question 4

A spreader bar is rated at 4.0 tonnes SWL. Due to the sling configuration, a deration factor of 0.75 applies. What is the maximum load that can safely be lifted?

Accepted Answer

3.0 tonnes

Answer

Applying the deration factor: 4.0t × 0.75 = 3.0 tonnes is the maximum allowable lift weight under these sling conditions.

Question 5

What is the main advantage of using a spreader bar when lifting a large-diameter thin-walled pipe?

Accepted Answer

It prevents inward compressive forces from the converging slings from crushing the pipe

Answer

A spreader bar keeps the slings from converging inward, preventing the crushing compressive forces that would otherwise be applied to the walls of a thin-walled pipe.

Rigging Licence Practice Test

Rigging Licence Practice Test

RB Spreader Bars and Lifting Beams 3