As the core of power transmission, the hydraulic system of the offshore crane needs to be maintained from three aspects: oil management, component inspection, and leakage prevention and control according to the characteristics of high pressure, humid environment, and frequent start and stop, and the following are the key points:
Oil management: the lifeline of system health
1. Oil quality control
- Regular sampling and testing: oil is analyzed with a spectrometer every 250 hours, and the oil must be changed when the metal particles > 50ppm or the acid value >0.5mgKOH/g;
- Temperature monitoring: The system's oil temperature needs to be controlled at 30-60°C. More than 70°C will easily lead to oil oxidation, and the cooler should be checked for blockage or overflow valve failure.
2. Pollution prevention and control
- Three-stage filtration: 80μm filter at the suction port, 25μm fine filter at the pipeline, 10μm filter element at the oil return port, and replace it regularly (every 500 hours);
- Waterproof and moisture-proof: The hydraulic tank respirator is equipped with a dryer, and the oil's water content is >0.1% when dehydrated by a vacuum oil purifier.
Inspection of core components: accurate positioning of hidden dangers
1. Pumps & Motors of the marine crane
- Abnormal noise troubleshooting: the axial piston pump emits a "buzzing" sound to indicate the evacuation of the suction; check the liquid level of the oil tank or the leakage of the suction pipe;
- Leak test: When the motor housing's oil discharge exceeds 50mL/min, the oil distribution pan is worn and needs to be disassembled and repaired.
2. Valve group and oil cylinder
- Reversing valve stagnation: After the operating handle returns to the center, the oil cylinder moves slowly, and the valve needs to be dismantled and cleaned (focusing on removing salt crystals);
- Cylinder leakage: When the luffing cylinder is loaded, the settlement exceeds 20mm within 10 minutes, the piston seal ring is aged, or the cylinder barrel is scratched.
Leakage and pressure management: eliminate power loss
1. Leakage prevention and control
- Joint sealing: Flange connection with hydraulic special O-ring (fluoroelastomer material anti-seawater corrosion), tightening torque according to the manufacturer's standard (e.g., M20 bolt up to 120N・m);
- Hose replacement cycle: The high-pressure hose in the marine environment is forced to be replaced every 1.5 years, and it will be stopped immediately if there is a bulge or exposed braid.
2. Pressure calibration
- System pressure holding test: the lifting circuit is pressurized to the rated pressure (such as 25MPa), the pressure drop is >0.5MPa within 10 minutes, and the nitrogen pressure of the accumulator or the internal leakage of the valve group needs to be checked;
- Safety valve setting: The valve shall be calibrated annually with a pressure calibration table, and the opening pressure deviation shall not exceed ±5% of the set value.
Environmental adaptability maintenance
- Anti-corrosion treatment: the exposed part of the piston rod of the cylinder is coated with molybdenum disulfide grease, and the salt is attached to it by rinsing it with fresh water every week;
- Low-temperature start: Before working below -10°C, run each mechanism without load for 15 minutes, and start the electric heating of the oil tank at the same time (the oil temperature needs to rise to more than 15°C);
- Post-typhoon inspection: focus on checking the loosening of pipe clamps in the open hydraulic pipeline to prevent vibration from causing joint thread wear.
Maintenance cycle and records
| Projects: | Daily Inspection | Monthly Inspection | Annual Overhaul |
| Oil Level | |||
| Filter Blockage Alarm | Replace all filters | ||
| Cylinder Settlement | Dismantling the inspection seal | ||
| System efficiency test | Full load action cycle |
Standardized maintenance can reduce the downtime rate of hydraulic system failures by 60% and maintain the power transmission efficiency above 90%, which is a key guarantee for the continuous operation of offshore cranes.
One-Stop Marine Mechanical Equipment Factory
YFM focuses on offshore cranes and has established an industry reputation for professional accumulation and innovation. The company's products cover large port cranes (intense lifting, high efficiency, helping port logistics), platform deck cranes (anti-marine environment, accurate lifting of materials), and small marine cranes (light and flexible, suitable for small ships) to meet diverse needs. All marine cranes have passed authoritative certifications from major classification societies such as China Classification Society (CCS), Det Norske Veritas (DNV), and other authoritative certifications, and strictly control the quality from design to testing to ensure that the products are safe, reliable, and stable in harsh sea conditions.