How is the boom length of a crane measured?

The boom length of a crane is measured from the boom foot pin to the center of the boom tip sheave pin. This measurement is standardized in crane operations because it provides a consistent and precise way to determine the working range and load capacity of the crane. The boom foot pin is where the boom connects to the crane structure, and the center of the boom tip sheave pin is the point where the load line exits the boom, which is crucial for understanding the mechanics of lift and extension.

Measuring from these two specific points ensures that the length accounts for the effective reach of the crane when in operation, allowing operators to calculate the crane's capabilities accurately. This method plays a significant role in safety and operational efficiency, as it directly impacts load charts and lifting calculations.

The other options either do not accurately reflect the standard measurement practices or involve points that do not provide a consistent reference for operational purposes.