Site and Lift Planning
Read the Site Before You Read the Chart
Lift planning starts with numbers you can defend. Establish the load's weight from drawings, shipping papers, or a scale - not from a guess - then add slings, shackles, the spreader beam, and any below-the-hook device. That total is what you compare against the crane's net capacity at the actual radius, measured horizontally from the center of rotation to the vertical line through the load's center of gravity. Confirm the chart configuration matches reality: boom length, jib stowed or deployed, counterweight, outriggers fully extended, and the capacity chart for that specific setup.
Ground is the second number. Estimate the load per outrigger float, then check it against soil bearing capacity with mats or cribbing sized to spread it. Compacted fill, asphalt over voids, and buried utilities all fail differently, and a load chart is only valid if the machine stays level.
Look up and around as well: power line approach distances, swing radius barriers, adjacent structures, wind sail area, and access routes for both the carrier and the load.
Traps in questions: measuring radius from the boom pivot or the near edge of the load instead of the center of gravity; deducting rigging weight but forgetting the spreader; quoting a chart for a longer boom than is actually pinned; treating a lift at 80% of capacity as routine. The 75% threshold is a common critical-lift trigger.
Rule of thumb: a 3 ft × 3 ft mat gives 9 ft². Thirty thousand pounds on one float is about 3,300 psf - more than most compacted soils will take, so go bigger.