What is a primary function of the radius indicator in crane operation?

The primary function of the radius indicator in crane operation is to indicate the distance from the center of rotation to the load. This measurement is crucial for safe crane operation because it helps the operator understand how far the load is from the pivot point of the crane. The radius, which is the distance from the center of rotation to the load, directly affects the crane's lifting capacity and stability.

Knowing the radius allows operators to ensure that they are within the safe operational limits of the crane. As the radius increases, the crane's lifting capacity generally decreases, and vice versa. Therefore, monitoring this distance is essential for preventing overloading, which can lead to accidents and equipment failure.

The other options, while related to crane operation, do not accurately describe the main function of the radius indicator. For instance, signaling two-blocking is related to load handling and safety systems in cranes but not specifically tied to radius measurement. Displaying the length of the boom is important for understanding the reach of the crane but does not provide information about the distance to the load. Showing the angle of the boom helps the operator understand the boom's position but again does not measure the radius from the center to the load.