Operating Radius
The horizontal distance from the crane's center of rotation to the center of the load being lifted.
In Detail
Operating radius is the horizontal distance measured from the center of the crane's rotation (center pin) to the center of the load hook (or the point where the load is attached). It is one of the primary variables determining rated capacity — as the radius increases, the available capacity decreases significantly. Operators must accurately determine the operating radius for every lift and reference the load chart accordingly. Boom deflection under load increases the actual radius beyond what the boom angle alone would indicate. Modern cranes with LMI systems calculate real-time radius automatically, but operators must still understand the concept for planning and safety.
Related Terms
Load Chart
A manufacturer-provided chart showing the maximum safe lifting capacities at various boom lengths and radii.
Rated Capacity
The maximum load a crane can safely lift at a given configuration, as specified by the manufacturer's load chart.
Boom
The primary structural member of a crane that extends outward and upward to position the hook over the load.
Lift Plan
A documented plan specifying the crane, rigging, load path, and safety procedures for a critical lift.