RB Spreader Bars and Lifting Beams 1 — Questions and Answers
Question 1: What is the primary purpose of a spreader bar in a rigging operation?
- To increase lifting speed by distributing crane hook load
- To hold sling legs apart and prevent inward compressive forces on the load (Correct answer)
- To replace shackles when lifting heavy structural members
- To extend the effective hook height of a crane
Correct answer: To hold sling legs apart and prevent inward compressive forces on the load
A spreader bar holds sling legs apart, preventing the inward compressive forces that would otherwise act on the load if slings converged directly toward the crane hook.
Question 2: What does the marking 'SWL' on a spreader bar indicate?
- Structural Weight Limit — the bar's own self-weight rating
- Standard Working Length of the bar
- Safe Working Load — the maximum load the bar can safely carry (Correct answer)
- Steel Weld Level — the quality grade of the bar's welds
Correct answer: Safe Working Load — the maximum load the bar can safely carry
SWL stands for Safe Working Load and indicates the maximum load the spreader bar is rated to safely carry under normal working conditions.
Question 3: Which type of force does a spreader bar primarily experience during a lift?
- Tension — because the slings pull it upward
- Torsion — because the load rotates during the lift
- Bending — because the load hangs from its centre
- Compression — because the sling legs push inward on both ends (Correct answer)
Correct answer: Compression — because the sling legs push inward on both ends
Sling legs converge toward the crane hook, pushing inward on both ends of the spreader bar and placing it under compressive force.
Question 4: What document must accompany an engineered spreader bar when used on an Australian worksite?
- The crane operator's daily log
- An engineer's design certificate or test certificate confirming the rated SWL (Correct answer)
- The site supervisor's written approval
- A current registration certificate from the state transport authority
Correct answer: An engineer's design certificate or test certificate confirming the rated SWL
An engineered spreader bar must be accompanied by a design or test certificate from a competent engineer confirming its rated SWL and fitness for purpose.
Question 5: Before each use, what is the minimum inspection requirement for a spreader bar?
- Hydraulic or ultrasonic testing of the bar's welds
- Disassembly and reassembly to check all internal components
- Visual inspection for cracks, deformation, corrosion, and legible SWL markings (Correct answer)
- Recertification by a licensed structural engineer
Correct answer: Visual inspection for cracks, deformation, corrosion, and legible SWL markings
A pre-use visual inspection checking for cracks, deformation, corrosion, and legible SWL markings is the minimum required before each use.
Question 6: What effect does increasing the length of a spreader bar have on the sling loads during a lift?
- Sling loads increase because each sling must support a greater span
- Sling loads remain constant regardless of bar length
- Sling loads decrease because the slings become more vertical (Correct answer)
- Sling loads double for every additional metre of bar length added
Correct answer: Sling loads decrease because the slings become more vertical
A longer spreader bar creates more vertical sling angles, which reduces the vector load on each sling and improves lifting efficiency.
Question 7: What is the minimum information that must be legibly marked on a spreader bar before it can be used?
- Manufacturer name and country of origin
- SWL and a unique identification number (Correct answer)
- The year of manufacture and material grade
- The name of the certifying engineer
Correct answer: SWL and a unique identification number
As a minimum, a spreader bar must be legibly marked with its Safe Working Load and a unique identification number for traceability and inspection purposes.
RB Spreader Bars and Lifting Beams 1
What is the primary purpose of a spreader bar in a rigging operation?