The Definition of Load Chart

Definition of Load Chart

A load chart is the table or set of tables provided by a crane manufacturer that shows the maximum load a crane can safely lift in each configuration. Rated capacities change with the boom length, the lift radius, the boom angle, the counterweight installed, the outrigger position and whether the load is lifted over the front, side or rear of the machine.

Every crane has its own load chart, and operators must use the chart for that specific machine and configuration. Load charts are usually kept in the cab, and many modern cranes also have a load moment indicator or rated capacity limiter that uses chart data to warn the operator when a lift approaches its limit.

OSHA's crane standard for construction, 29 CFR 1926 Subpart CC, requires that cranes not be operated beyond the manufacturer's rated capacity and that the load chart be available to the operator at the control station. ASME B30.5 sets similar requirements for mobile cranes.

How to Read a Load Chart

Key terms

• Radius: the horizontal distance from the crane's center of rotation to the center of the hook or load. Capacity drops quickly as radius increases.
• Boom length: how far the boom is extended. Longer booms generally reduce capacity.
• Boom angle: the angle of the boom above horizontal, which links boom length and radius.
• Gross capacity: the total rated load from the chart before deductions.
• Net capacity: what is left for the actual load after subtracting the weight of the hook block, slings, spreader bars and other lifting attachments.

Structural and stability limits

Many load charts are split into areas limited by structural strength and areas limited by stability. At short radius, the boom or other parts may fail before the crane tips. At long radius, the crane may tip before anything breaks. Operators should know which limit applies to their lift, because tipping can happen with little warning.

Chart notes

The notes printed with the chart are as important as the numbers. They often specify that capacities apply only on firm, level ground, with outriggers fully extended, in limited wind, and with certain deductions for attachments. Ignoring the notes can lead to overloading even when the main table seems to allow the lift.

Using Load Charts Safely

• Confirm the exact load weight, including all rigging, before the lift.
• Measure or calculate the actual radius at pick-up, travel and set-down, using the largest radius.
• Select the chart that matches the crane's current setup and quadrant of operation.
• Subtract all deductions to find net capacity.
• Build in a margin. Many companies treat lifts above a set percentage of capacity as critical lifts that need a formal lift plan.
• Do not rely only on electronic limiters. Operators should still check the chart manually.

Load chart use is a core part of crane operator training and certification. Related equipment, such as jib cranes and knuckle boom cranes, have their own capacity charts or plates.

Example of Load Chart

A crane operator was asked to lift a precast concrete panel weighing 9,000 pounds. The panel would be picked at a 40-foot radius and set at 55 feet. Checking the load chart for the crane's boom length and full outrigger setup, the operator found a gross capacity of 14,200 pounds at 55 feet. After deducting 650 pounds for the hook block and 300 pounds for slings and a spreader bar, net capacity was 13,250 pounds.

The lift was within capacity at about 75 percent of the chart rating. However, the site's lifting procedure required a critical lift plan for any lift above 75 percent, so the operator paused and the lift supervisor completed and approved a plan before the panel was moved.

Frequently Asked Questions: Load Chart

Why does crane capacity go down as radius increases?

As the load moves farther from the crane, it creates a larger tipping moment. The crane must resist that moment with its counterweight and outriggers, so the allowable load decreases.

Do I have to include rigging weight?

Yes. Hooks, blocks, slings, shackles and spreader bars are all part of the load the crane is lifting and must be subtracted from the chart capacity.

Can a load chart from a similar crane be used?

No. Operators must use the load chart for the specific crane, serial number and configuration being used.