What safety feature must hydraulic cranes have to ensure they do not lower unexpectedly?

Hydraulic cranes are equipped with holding valves as a critical safety feature to prevent unintended lowering of the load. Holding valves are designed to maintain hydraulic pressure in the system when the crane is not actively in operation or when there is a loss of pressure elsewhere in the hydraulic system. This mechanism allows the crane to support the load securely in the raised position, effectively preventing any sudden or unintended descent that could result from hydraulic leaks or system failures.

This feature is particularly important in maintaining safety on job sites, as unexpected lowering can pose significant risks to workers and equipment. Holding valves ensure that the load remains stable and secure, contributing to the overall reliability and safety of hydraulic cranes in lifting operations.