Which limiting device helps in controlling the angle of the boom?

The boom angle indicator is specifically designed to measure and display the angle of the boom relative to the horizontal plane. This tool provides crucial information to operators about how high or low the boom is positioned, which is essential for ensuring safe and efficient crane operation. Maintaining the correct boom angle is critical for achieving desired lifting capabilities and preventing accidents due to instability.

While other devices, such as the luffing jib limiting device, may control the movement of the jib and the overall configuration of the crane, they do not specifically measure or control the angle of the boom itself. Similarly, the boom length indicator and the radius indicator provide information about the boom's length and the distance from the pivot point to the load, but they do not address the angle of the boom directly. Thus, the boom angle indicator is the appropriate choice for controlling and monitoring the boom's angle.