Load Charts, Capacity, and Stability
What this domain covers
Load Charts, Capacity, and Stability tests whether you can select the correct chart, apply deductions, and recognize when stability or ground conditions govern.
Rules
- Use the manufacturer's chart for the exact configuration: boom length, jib, counterweight, outrigger spread, track gauge, leads, hammer, and pile cap.
- Determine radius at the load's center of gravity, not the boom tip. Apply all deductions for attachments, rigging, and the pile.
- Keep the pile load within rated capacity throughout the lift, including pick-up, swing, and placement. Consider wind, dynamic starts and stops, side loading, and extraction resistance.
- A load moment indicator aids the operator but does not replace the chart or the operator's judgment. Stability can govern before the structural rating is reached.
- Check ground bearing and levelness; an outrigger sinking changes radius and can overload the boom.
Worked example
At a 30-ft radius the chart allows 18,000 lb. Deductions are 3,000 lb for leads and hammer, 600 lb for rigging, and 2,400 lb for the pile, totaling 6,000 lb. Remaining capacity is 12,000 lb, so the lift is acceptable only if no dynamic or wind penalty applies. If the pile must be dragged sideways because it is not under the boom, the side load is outside the chart and the lift must be replanned.
Traps
Reading radius to the boom tip; using the crane chart when the pile driver attachment changes ratings; omitting the pile weight; and assuming a level-looking pad proves stable ground.