Methods for diagnosing failures in the safe unloading function of cranes
Thread Content
The safe unloading of cranes is achieved through the combined action of a torque limiter, an overload unloading solenoid valve, and pilot-controlled hydraulic systems such as logic valves or limit switches. Safe unloading operations generally feature good responsiveness, making them a very popular safety device in cranes. However, failures in the crane’s electrical or hydraulic system can also often cause it to fail to unload safely; in such cases, it is necessary to use our insight to identify the root cause of the problem. The failure of a crane’s safe unloading function is mainly considered from two aspects: the electrical circuit and the hydraulic system. When checking the circuit, if the alarm signal from the panel indicator is successfully transmitted to the unloading solenoid valve, it indicates that safe unloading is working properly; otherwise, safe unloading will fail. After checking the electrical circuit, check the hydraulic circuit as well. In a hydraulic system, if the spring of the check valve inside the logic valve is too stiff or if the diameter of the valve opening is too small, it can prevent the unloading oil circuit from functioning properly, thereby preventing the crane from unloading safely. Therefore, when such fluid circuit failures occur, the layout of the logic valves should be adjusted accordingly. Furthermore, once the causes of failure in the safe unloading function of the crane are identified, improvements should be made promptly. To ensure safe unloading, it is advisable to use the crane again after testing, which enhances its safety level.
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