Load Control, Center of Gravity & Rigging Techniques
Controlling loads with taglines, balancing CG, using spreader bars, choker placement, and rigging cylindrical/irregular loads.
- Explain how to locate and balance center of gravity for stable lifts
- Describe proper tagline use, swivels, and rotation control methods
- Identify spreader bar and equalizer applications for angle management
- Apply rigging techniques for pipes, bundles, and irregular shapes
- Explain plumb hook positioning and the risks of short sling legs
Lesson 1
Center of Gravity - Finding & Balancing Loads
Why Center of Gravity Matters
The center of gravity (CG) is the single most important concept in load control. The load must be rigged so the CG is directly below the crane hook. If the CG is not under the hook, the load will tilt, swing, or spin when lifted - creating a dangerous uncontrolled condition.
Critical Exam Concept
The load must be rigged so the center of gravity is directly below the hook to prevent tipping and uncontrolled swing. This is tested repeatedly on the NCCCO exam.
Finding the CG
For symmetrical loads (steel beams, uniform plates), the CG is at the geometric center. For asymmetrical or irregular loads, the CG shifts toward the heavier end. Methods to find CG:
- Manufacturer data - shipped equipment often has CG marked
- Visual inspection - identify the heavier end or section
- Trial lift - lift a few inches, observe tilt, adjust rigging
- Calculation - use weight distribution data when available
Adjusting for Off-Center CG
When the CG is not at the geometric center:
- Shorten the sling on the heavy side to bring the hook point closer to the CG
- Move attachment points toward the heavy end
- Use unequal leg lengths in a bridle to shift the balance point
The load must be rigged so the center of gravity is directly below the crane hook. Always perform a trial lift a few inches off the ground to verify balance before committing to the full lift.