To ensure safe and reliable lifting operations, cranes are equipped with comprehensive safety devices to protect machine components or alert operators in case of emergencies, thus providing safety protection.
1. Relief valves in the hydraulic system: These suppress abnormal high pressure in the circuit, preventing damage to the hydraulic pump and motor, and preventing overload.
2. Boom luffing safety device: In the event of an unforeseen accident, such as a burst or severed high-pressure hose or oil pipe in the boom luffing cylinder circuit, the balance valve in the hydraulic circuit activates, locking the working oil from the lower chamber of the cylinder, preventing the boom from falling and ensuring operational safety.
3. Boom extension safety device: In the event of an unforeseen accident, such as a burst or severed high-pressure hose or oil pipe in the boom extension cylinder circuit, the balance valve in the hydraulic circuit activates, locking the working oil from the lower chamber of the cylinder, causing the boom to retract automatically, thus ensuring operational safety.
4. Height Limit Device: After the hook is raised to the specified height, it contacts the limit counterweight, activating the limit switch. The "over-winding" indicator light illuminates, simultaneously cutting off hook raising, boom extension, and boom lowering operations to ensure safety. At this point, simply operating the hook lowering, boom retraction, or boom raising (i.e., operating in the safe direction) handles releases the limit counterweight, and normal operation resumes. In special circumstances where a small over-winding operation is still necessary, the release button on the instrument panel can be pressed. This releases the limit function, but extreme caution must be exercised during this operation to prevent accidents.
5. Outrigger Locking Device: In the event of an unforeseen accident, such as a rupture or cut in the high-pressure hose or pipe leading to the outrigger vertical cylinder, the bidirectional hydraulic lock in the hydraulic system seals the pressure oil in both chambers of the outrigger locking cylinder, preventing the outrigger from retracting or extending, thus ensuring the safety of lifting operations.
6. Lifting Capacity Indicator: The lifting capacity indicator is located on the side of the main boom (i.e., the right side of the operator's cab), clearly visible to the operator from inside the cab. It accurately indicates the boom's elevation angle and the crane's permissible rated lifting capacity under corresponding working conditions.
7. Lifting Characteristic Table: Located on the lower front wall panel inside the operator's cab, this table lists the rated lifting capacity and lifting height for various boom lengths and working radiuses for easy reference during operation. During lifting operations, the values specified in the table must never be exceeded.
