At the equipment installation site of a chemical industrial park in a certain city, a SANY STC500 truck crane was performing the hoisting task of a 25-ton reactor. When the main arm was extended to a 32-meter radius with an elevation angle of 70°, the operator suddenly noticed that the main arm continued to sink without any operation, dropping a total of about 8cm within 5 minutes, and at the same time, the left outrigger showed slight retraction. The on-site supervisor immediately issued a shutdown order - if the operation continued, it might cause the whole machine to overturn due to the shift of the center of gravity. After the technical team arrived, it was initially determined that the main arm cylinder (HSGK200/110-1800) and the outrigger cylinder (HSGK180/100-900) had internal leakage problems, which were directly related to the operating habit of not performing timely maintenance after 12 hours of continuous heavy-load operation three days ago.
Solution:
Maintenance Methods
| Cylinder type | Model specification | Bore / Rod diameter | Stroke | Rated pressure | Sealing material |
| Main arm cylinder | HSGK220/125-2000 | 220mm/125mm | 2000mm | 32MPa | PTFE + PU |
| Jib cylinder | HSGK160/90-1500 | 160mm/90mm | 1500mm | 28MPa | Polyurethane (PU) |
| Outrigger cylinder | HSGK190/110-1000 | 190mm/110mm | 1000mm | 26MPa | Polyurethane (PU) |
1. Repair of outrigger cylinder sinking (retraction)
• Disassemble the oil cylinder, replace the piston seal with a new suitable model, carefully inspect the surface of the cylinder barrel and piston, and if there is wear, repair it by grinding and other processes.
• Inspect the control valve, and if the valve core or seal is damaged, replace it in time to ensure good sealing performance of the valve core.
2. Repair of poor telescoping of main arm cylinder
• Inspect the hydraulic oil circuit of the main arm cylinder, remove impurities and blockages in the oil circuit, and replace aging hydraulic oil pipes.
• Inspect the piston rod inside the oil cylinder. If there is bending, use professional equipment to straighten it; if the guide sleeve is severely worn, replace it with a new one in time.
3. Repair of abnormal noise of jib cylinder
• Check the oil quantity and quality of the hydraulic oil in the jib cylinder. If the oil quantity is insufficient, replenish it in time; if the oil quality deteriorates, replace all with new suitable hydraulic oil.
Disassemble the oil cylinder, check whether the internal parts are loose or damaged, fasten the loose parts, and replace the damaged parts.
