Cranes and derricks with variable-angle booms must be equipped with what essential indicator?

Cranes and derricks that utilize variable-angle booms require an angle indicator as an essential component for safe and effective operation. An angle indicator provides the operator with real-time data on the boom's angle relative to the ground or its horizontal position. This information is crucial because the load capacity of a crane significantly fluctuates based on the angle of the boom. By knowing the exact angle, the operator can make informed decisions about load limits and adjustments during lifting operations, ensuring that the crane is used within its safe working range. This prevents accidents and equipment failures that can arise from overloading or improper use based on an incorrect understanding of the boom's position.

While a load weight indicator is useful for understanding the weight being lifted, and a height indicator can assist in ensuring that lifts do not exceed vertical clearances, it is the angle indicator that directly relates to the specific dynamics of boom operation and load stability. Therefore, it holds an essential place in the equipment’s safety and operational effectiveness.