Which technique involves using a plumb bob to verify that the crane is level?

• A. Place a level at two points on the slew gear perpendicular to each other
• B. Raise the boom to a high angle, lower the load line close to the ground, and swing while watching to see if the load line stays in line with the boom (a plumb bob)
• C. Raise the boom to a high angle and slowly swing while watching the LMI values for boom angle
• D. Use a laser level at the cab

Answer: (B)

Using a plumb bob provides a true vertical reference to gravity, which lets you verify that the crane’s load path stays aligned with the boom as you move. By raising the boom, lowering the load line toward the ground, and then swinging while watching the load line in relation to the plumb bob, you’re checking whether the line of action of the load remains in line with the boom. If it does, the crane is effectively level with respect to gravity; if not, you’ve got a tilt or out-of-level condition to address. This direct, gravity-based check is why this technique is the appropriate method.

Other methods don’t use the plumb bob as the vertical reference and therefore don’t test level in the same way: placing a level on the slew gear checks the machine’s alignment but not the load path during swing; following LMI readings focuses on angles and load calculations rather than true vertical alignment; a laser level from the cab provides a level reference without the plumb-bob comparison.