Millwright Certification Rigging Techniques 2

Question 1

What is the purpose of a tag line when performing a crane lift?

Accepted Answer

To control the load's rotation and prevent it from spinning or swinging during the lift

Answer

Tag lines are ropes attached to the load that riggers hold to control the load's orientation, preventing it from spinning, swinging, or contacting structures during lifting and travel.

Question 2

What is the safe working load (SWL) of a sling, and how does it relate to the breaking strength?

Accepted Answer

SWL is the maximum load a sling can safely lift, calculated by dividing the breaking strength by a safety factor (typically 5:1 for wire rope slings)

Answer

Safe Working Load (SWL) or Working Load Limit (WLL) is the maximum load a sling is rated to lift in normal service. It equals the breaking strength divided by the design safety factor (typically 5:1 for wire rope, 5:1 for chain).

Question 3

How does the sling angle affect the load on each leg of a multi-leg sling arrangement?

Accepted Answer

As the sling angle from vertical decreases (spreads wider), the load on each sling leg increases due to the horizontal force component

Answer

As sling legs spread wider from vertical, each leg must carry more load to produce the same vertical lifting force. At 60 degrees from vertical, each leg carries the full load weight; at 45 degrees, each carries 1.41 times its share.

Question 4

What is a basket hitch, and when is it appropriate to use?

Accepted Answer

A sling passed under the load with both ends attached to the hook, doubling the sling capacity for loads that are stable and balanced

Answer

A basket hitch passes the sling under the load and attaches both end fittings to the crane hook, effectively creating a U-shaped cradle. This configuration doubles the sling's rated capacity because the load is shared between two legs.

Question 5

Before performing any lift, what is the first thing a rigger must determine?

Accepted Answer

The weight of the load, including the weight of rigging hardware attached to it

Answer

Knowing the exact weight of the load (plus rigging hardware) is the fundamental first step in any lift plan because all rigging selections (crane capacity, sling ratings, shackle sizes, and rigging configuration) depend on the load weight.

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Millwright Certification Rigging Techniques 2