RB Spreader Bars and Lifting Beams 2 — Questions and Answers
Question 1: How does a lifting beam differ structurally from a spreader bar?
- A lifting beam is made of aluminium; a spreader bar is always made of steel
- A lifting beam resists bending moments; a spreader bar resists compression (Correct answer)
- A lifting beam is used only overhead; a spreader bar is used at ground level
- A lifting beam has a fixed SWL; a spreader bar's SWL varies with configuration
Correct answer: A lifting beam resists bending moments; a spreader bar resists compression
A lifting beam is designed to resist bending (flexural) forces from loads suspended below it, while a spreader bar is designed to resist compressive forces from inward-pulling slings.
Question 2: As the sling angle measured from vertical increases beyond 45 degrees when used with a spreader bar, what happens to the compressive force in the bar?
- The compressive force decreases as the slings become more spread out
- The compressive force remains constant regardless of sling angle
- The compressive force increases significantly (Correct answer)
- The compressive force reverses and becomes tensile
Correct answer: The compressive force increases significantly
As sling angles increase beyond 45° from vertical, the horizontal component of sling forces grows rapidly, driving up the compressive load on the spreader bar.
Question 3: Under which circumstance must a spreader bar be immediately removed from service?
- When it has been used more than 100 times in a 12-month period
- When the rigging configuration changes between consecutive lifts
- When visible cracks, deformation, or missing/illegible SWL markings are found (Correct answer)
- When the ambient temperature on site exceeds 30°C
Correct answer: When visible cracks, deformation, or missing/illegible SWL markings are found
Visible cracks, deformation, or missing/illegible SWL markings indicate compromised structural integrity, requiring immediate removal from service.
Question 4: Which Australian standard specifically covers the design and use of lifting devices such as spreader bars and lifting beams?
- AS/NZS 3000 (Wiring Rules)
- AS 4991 (Lifting devices) (Correct answer)
- AS 1576 (Scaffolding)
- AS 3569 (Steel wire ropes)
Correct answer: AS 4991 (Lifting devices)
AS 4991 (Lifting devices) is the Australian standard specifically covering the design, manufacture, testing, and safe use of lifting devices including spreader bars and lifting beams.
Question 5: If a spreader bar's test certificate cannot be located on site, what must the rigger do?
- Proceed with the lift at 50% of the marked SWL as a precaution
- Obtain verbal confirmation of the SWL from the site supervisor
- Not use the spreader bar until a valid certificate is produced (Correct answer)
- Use the bar only for loads under 1 tonne regardless of the markings
Correct answer: Not use the spreader bar until a valid certificate is produced
Without a valid test certificate, the spreader bar's design and rated SWL cannot be verified, so it must not be used until proper documentation is produced.
Question 6: Where should the crane hook attach when a spreader bar is rigged for a standard lift?
- To one end of the spreader bar to keep the hook centred over the load
- To the central lifting lug or pick point on top of the spreader bar (Correct answer)
- Directly to the load's slings, bypassing the bar entirely
- To the slings at mid-span between the bar and the load
Correct answer: To the central lifting lug or pick point on top of the spreader bar
The crane hook must attach to the central lifting lug on top of the spreader bar to ensure the load is balanced and the bar is loaded correctly.
Question 7: What is the function of end retention pins or end stops on a spreader bar?
- To adjust the rated SWL of the bar for different load weights
- To indicate the maximum safe extension length of the bar
- To prevent slings from sliding off the end fittings during the lift (Correct answer)
- To connect the spreader bar directly to the crane's main hook block
Correct answer: To prevent slings from sliding off the end fittings during the lift
End retention pins and stops are safety devices that prevent slings from accidentally sliding off the end fittings of the spreader bar during a lifting operation.
RB Spreader Bars and Lifting Beams 2
How does a lifting beam differ structurally from a spreader bar?