Crane safety devices: safety devices luffing jib. When the mishap occurred, boom luffing cylinder loop burst high-pressure hose or tubing or cut off, the hydraulic circuit balancing valves on the work, the lower chamber of the cylinder lock from operating oil boom will not fall so heavy cranes to ensure the safety of operations. Crane safety devices: the height limit device. For special occasions, such as still need to make small amounts of over-winding operation, press the release button on the meter box buy heavy cranes, then the role will be to lift the limit, but this time the operation must be very careful to avoid accidents . Telescopic crane safety device: When unexpected accident, telescoping boom cylinder circuit of high-pressure hose or pipe burst or cut off, the hydraulic circuit balancing valves to work used heavy cranes, locked from the fuel tank under the working oil chamber so hang retract on their own, so as to ensure the safety of operations.