n a construction site in the city, a Sany Heavy Industry STC250C4 crane was working intensively. However, recently, the operator found that the crane's boom extension and luffing movements became slow and unstable, and sometimes even abnormal jitters occurred. This not only seriously affected the construction progress but also brought potential safety risks. After preliminary inspection, it was judged that the problem lay in the hydraulic system. In order to make this "steel giant" regain its vitality, our maintenance team quickly intervened and launched a "battle" against the failure.
Solution:
Troubleshooting
Comprehensive Inspection: Conduct a comprehensive visual inspection of the hydraulic system. Check if there are any looseness, damage, cracks, or oil leaks in the hydraulic oil tank. During the inspection, a small amount of oil seepage was found at the bottom of the tank. At the same time, check the hydraulic oil level, contamination level, and viscosity. It was found that the hydraulic oil was severely contaminated and had exceeded the normal standard.
Key Component Detection: Use professional tools to detect the working status of the hydraulic pump, including abnormal noise, vibration, and heating, as well as the normal supply pressure. The test results showed that the supply pressure of the hydraulic pump was lower than the specified value, and there was obvious abnormal noise during operation. Further inspection of the pipeline joints found that some joints were loose and leaking, which may lead to system pressure leakage and affect the overall performance.
Precision Component Inspection: For the key control components in the hydraulic system, such as balance valves and one - way throttle valves, carefully check their working status. Through professional instrument testing, it was found that the spool of the balance valve had a certain degree of wear, which may be one of the important reasons for the unstable operation of the boom.
Fault Summary: Based on the comprehensive inspection results, the main problems existing in the hydraulic system were determined as follows: severe hydraulic oil contamination, decreased working performance of the hydraulic pump, loose and leaking pipeline joints, and wear of the balance valve spool. These problems interacted with each other and jointly led to the fault performance of the crane hydraulic system.
Component Replacement
Replace Hydraulic Oil and Filter: Select high - quality hydraulic oil that meets the equipment requirements. Completely drain the original contaminated hydraulic oil and replace it with a new hydraulic oil filter. During the replacement process, strictly follow the operating specifications to ensure the accurate addition of new oil and the firm installation of the filter without leakage risk.
Replace Hydraulic Pump: After determining the model and specifications of the hydraulic pump, purchase a new hydraulic pump that is suitable for the equipment. When replacing, first turn off the power of the hydraulic system, release the system pressure, and then carefully remove the faulty hydraulic pump, record the disassembly sequence and relevant parameters. Clean the installation surface of the hydraulic pump and the installation seat on the equipment to ensure that the surface is clean and free of oil stains. Install the new hydraulic pump in the reverse order of disassembly, ensuring firm connection and good sealing.
Handle Pipeline Joints: Handle all loose and leaking pipeline joints. Disassemble the joints, check whether the seals are damaged, and replace them with new seals if damaged. When reinstalling the joints, use appropriate tools to tighten them according to the specified torque to ensure that the joints are firmly connected and free of leakage.
Replace Balance Valve: Purchase a balance valve of the same model as the original for replacement. First release the system pressure, remove the old balance valve, and clean the installation position. When installing the new balance valve, pay attention to the correct installation direction of the spool to ensure its normal operation.
System Debugging
System Oil Filling: After completing the component replacement, carry out system debugging. First, add hydraulic oil to the specified oil level and ensure that there are no air bubbles remaining in the system through specific operations, providing good basic conditions for the normal operation of the system.
Pressure Adjustment: Start the hydraulic system and slowly adjust the pressure to the set value step by step. At the same time, closely monitor the changes of the pressure gauge to ensure that the pressure adjustment process is stable without abnormal fluctuations.
Function Testing: Conduct a comprehensive function test on the hydraulic cylinders, motors, and various control valves of the crane, checking their response speed and action accuracy. During the test, simulate the actual working conditions of the crane, including boom extension, luffing, and slewing actions, to ensure that the system operates smoothly and all components work together normally.
Data Recording: Record in detail all the data during the debugging process, including pressure, flow, temperature, etc., to form a complete test report. These data not only help to determine whether the system has returned to normal but also provide an important reference for subsequent equipment maintenance.
Solution Results
Performance Restoration: After a series of maintenance and debugging work, the performance of the crane's hydraulic system has been significantly restored. The boom extension and luffing actions have become smooth again, and the speed and power have reached the normal standards of the equipment. In actual operation, it can quickly and stably complete various hoisting tasks, greatly improving the construction efficiency.
Stability Improvement: After the troubleshooting of the hydraulic system, the stability of the crane during operation has been significantly enhanced. The abnormal jitter phenomenon has disappeared, and the equipment operates more smoothly and reliably, effectively reducing safety risks and providing a strong guarantee for safe production at the construction site.
Data Compliance: Through the data recording and analysis during the debugging process, all key parameters meet the technical requirements of the equipment. The pressure, flow, and temperature indicators are stable within the normal range, indicating that the hydraulic system has returned to a good working state.
Customer Feedback: The equipment operators and the construction party gave high praise to the performance of the repaired crane. They said that the performance of the crane has returned to its original state, the construction progress can be smoothly advanced, and they recognized and thanked the maintenance team for their professional ability and efficient service.
