The hydraulic system of a cutter suction dredger is responsible for driving core components such as the cutter, positioning piles, and traversing winches. Due to the harsh operating environment (high load, complex water conditions), the stability of the hydraulic system directly determines the construction efficiency.
I. Daily Maintenance
The core of maintenance lies in "cleanliness" and "monitoring". More than 70% of hydraulic system failures are caused by oil contamination.
1. Pre-operation Inspection (Shift Maintenance)
1.1 Oil Level Inspection
Ensure the hydraulic oil tank level is at 1/2 ~ 2/3 of the level gauge. Too low a level will cause cavitation due to pump suction, while too high a level will easily lead to oil temperature rise.
1.2 Leakage Check
Walk around the dredger to check for leaks at hydraulic pumps, motors, oil cylinders and pipeline joints. Focus on whether oil drips out of the piston rod (normal condition is oil film wetting).
1.3 Vent Hole Cleaning
Check if the tank vent hole is blocked. If blocked, a vacuum will form inside the tank, causing difficulty in oil suction by the pump.
1.4 Fasteners
Check if connecting bolts and base bolts are loose, especially at the joints of hydraulic motors and pumps.
2. Listening, Observing and Measuring During Operation
2.1 Listening
2.1.1 Cavitation Noise
If the pump emits a sharp squeal or "clicking" sound, it is usually insufficient oil suction or air leakage in the oil suction pipe.
2.1.2 Abnormal Noise
Periodic knocking noise may indicate gear pump tooth surface wear or bearing damage.
2.2 Observing
2.2.1 Actuator Observation
Observe whether actuators (such as cutter lifting, pile carriage movement) have crawling, jamming or slow movement, which is usually caused by valve core stuck or excessive internal leakage due to oil contamination.
2.2.2 Pressure Gauge Observation
Observe whether the pressure gauge pointer fluctuates violently.
2.3 Measuring Temperature
2.3.1 Temperature Range
Regularly detect the temperature of pump casing, valve group and pipelines with an infrared thermometer. The ideal operating temperature of hydraulic oil is usually 30°C ~ 60°C, and the maximum shall not exceed 82°C.
2.3.2 Temperature Difference Check
If the local temperature difference exceeds 10°C, check for heat dissipation or internal leakage problems.
3. Periodic Maintenance (Monthly/Quarterly/Yearly)
3.1 Filter Element Replacement
Replace return oil filters and oil suction filters according to operating hours (usually 500 hours or quarterly). Check the seal of the mounting seat during replacement to prevent bypass contamination.
3.2 Oil Inspection
Sample and test viscosity, acid value and cleanliness (NAS grade) quarterly. If the oil turns black, has a burnt smell or the viscosity drops by 15%, replace the oil in advance.
3.3 Lubrication
Strictly lubricate all hinge points, pulleys and steel wire ropes according to the lubrication cycle table.
II. Hydraulic System Maintenance
Operators shall carry out daily maintenance of the hydraulic system on the basis of mastering the principle of the hydraulic system of the dredger. The fundamental task is to closely monitor the working process of the hydraulic system, find unfavorable factors in time, analyze the operating status of the system from various aspects, and eliminate hidden dangers before failures occur.
1. Maintain Normal Oil Tank Level
The hydraulic system has many oil pipes and pumps with large capacity. After operation, the oil tank level drops as the oil circulates into the system. If it is lower than the specified value, replenish hydraulic oil in time. Leakage is inevitable in normal operation, so observe frequently to ensure the normal level.
2. Cleanliness and Qualified Grade of Hydraulic Oil
2.1 Oil Standard
Add hydraulic oil meeting national standards as required, usually 46# anti-wear hydraulic oil.
2.2 Replacement Cycle
Inspect and replace hydraulic oil regularly, generally every half a year to one year. Adjust the replacement cycle reasonably according to the operating environment and working hours.
2.3 Oil Replacement Requirement
Replace oil that has oxidized, deteriorated, severely contaminated or degraded in performance in time.
2.4 Oil Change Procedure
When changing oil, drain the hydraulic oil in pipelines, valve bodies and oil cylinders as much as possible, and clean the valve cores and filters. Hydraulic oil must be added from the specified oil filling port with a filter screen.
2.5 Cleaning Notice
When cleaning filter elements and screens in oil, avoid falling of cotton yarn, cloth scraps and other debris.
3. Appropriate Oil Temperature
The oil temperature shall not exceed 60°C, and the optimal range is 35°C ~ 60°C. Excessively high oil temperature will easily oxidize and deteriorate the oil.
4. Prevent Air Suction in the System
Drain all existing air completely to prevent system crawling and oil deterioration. Drain water at the bottom of the oil tank regularly.
5. Initial Start-up of Hydraulic Pump
Fill oil into the hydraulic pump before initial start-up. The purpose is to speed up oil output, prevent air from entering and causing dry grinding of the hydraulic pump due to idle rotation.
6. Relief Valve Pressure Setting
The set pressure of the relief valve shall not exceed the maximum system pressure.
7. Component Adjustment Rules
Keep in mind the rotation direction of adjusting handles of various hydraulic components and the relationship between pressure and flow. Prevent adjustment errors and accidents. If the equipment is not used for a long time, loosen all hydraulic components and return the oil to the tank as much as possible to prevent deformation or damage of hydraulic components due to long-term stress.
8. Standardized Maintenance
Carry out inspection and maintenance strictly in accordance with the maintenance system, inspection items and cycles. Establish maintenance files, accumulate data and explore rules.
Cutter Suction Dredger Hydraulic Schematic Diagram :
III. Common Fault Analysis
Generally speaking, the hydraulic system is safe and reliable, with the advantages of high efficiency, small size and convenient operation. However, failures are easy to occur due to improper adjustment and inattention during operation. Since all hydraulic components operate in a sealed system, it is not easy to find the cause and eliminate failures in time when they occur.
1. Insufficient or No Pressure in the Hydraulic System
1.1 Troubleshooting Methods
1.1.1 Pump Oil Discharge Check
First, check whether the pump discharges oil. If not, the possible reasons are wrong pump rotation direction, serious component wear, large resistance or air leakage in the oil suction pipe. For a new pump, it is most likely due to internal air, sand holes in the pump casing, low pump speed and low oil discharge.
1.1.2 Relief Valve Check
If the hydraulic pump discharges oil, check the return circuit to see where the oil returns. If the oil returns from the relief valve, it indicates that the set pressure of the relief valve is low. If there is still no pressure after tightening the relief valve spring to the specified value, it is most likely that the relief valve core is stuck, the spring fails or the damping hole is blocked.
1.1.3 Pressure Circuit Check
If the fault is not eliminated after checking and cleaning the relief valve, some valves in the pressure oil circuit may be stuck in the return position due to dirt or other reasons, resulting in a short circuit between the pressure oil circuit and the return oil circuit.
1.1.4 Hydraulic Pump Efficiency Check
If the pressure can be adjusted through the relief valve, but the flow rate of the hydraulic pump decreases significantly with the increase of pressure, and the pressure cannot reach the required value, the hydraulic pump may be seriously worn.
1.1.5 Local Pressure Check
If normal pressure can be established in the whole system, but there is no pressure in some pipelines or hydraulic cylinders, it may be blocked at small pipeline holes or throttle valves.
2. Insufficient or No Movement Speed of Working Mechanism
2.1 Main Causes
2.1.1 Hydraulic Pump Oil Suction Problem
Wrong rotation direction of the hydraulic pump or insufficient oil suction of the hydraulic pump, which may be caused by excessive resistance of the oil suction pipe, too low oil tank level, air leakage in the suction pipe, too viscous oil or too low oil temperature, too low speed, etc.
2.1.2 Hydraulic Pump Internal Leakage
Serious internal leakage of the hydraulic pump, caused by serious internal wear, increased sealing clearance, sand holes or cracks in the hydraulic pump casing.
2.1.3 Valve Core Stuck
The valve bodies and cores of the relief valve or pressure circuit are stuck by impurities or rust.
2.1.4 Sealing and Wear Problem
Excessive wear of pipe joints of pressure oil circuit, valve cores of directional valves and valve holes, and serious internal leakage due to damaged sealing devices of hydraulic cylinders.
2.1.5 Relief Valve Pressure Too Low
The set pressure of the relief valve is too low.
3. Noise and Vibration
3.1 Main Causes
3.1.1 Air in System
Air in the system, especially in the oil suction pipe, will produce great noise.
3.1.2 Hydraulic Pump Problem
Caused by the hydraulic pump. If the hydraulic pump has large pulsation, insufficient elimination of oil trapping, stuck or broken blades of vane pumps, broken gear teeth of gear pumps, loose fixing of the hydraulic pump casing, loose coupling, and misalignment between the pump and the output shaft of the main engine.
3.1.3 Pipeline and Valve Problem
Caused by oil pipes and valves. If the pipeline is slender and not rigidly fixed, the oil flows fast in the pipe, causing pipeline vibration; valve bodies such as relief valves resonate due to the natural frequency close to the pulse frequency of the hydraulic pump.
4. Uneven Movement of Working Components
4.1 Main Causes
4.1.1 Air in Hydraulic System
Air in the hydraulic system. Due to the dissolution and separation of air in the oil to produce foam and its own compressibility, the medium becomes an elastic fluid, causing uneven movement of moving parts.
4.1.2 Poor Lubrication or Jamming
Poor lubrication between moving parts or jamming due to damaged parts.
4.1.3 Deformation of Moving Parts
Deformation between moving parts, causing uneven friction.
4.1.4 Back Pressure Problem
Insufficient back pressure setting or poor contact at the back pressure setting part.
5. Excessively High Oil Temperature
5.1 Main Causes
5.1.1 Serious leakage leading to low efficiency
5.1.2 Excessively high system pressure regulation leading to low efficiency
5.1.3 Failure or absence of system pressure relief measures
5.1.4 Too small oil tank, poor heat dissipation, or insufficient heat dissipation capacity of the cooler
5.1.5 Excessively high oil viscosity and excessively fast oil flow rate, causing excessive friction loss and overheating
5.1.6 Increased pipeline throttling, additional throttling loss due to pipeline damage or local blockage, increasing heat generation
5.1.7 Excessively high operating environment temperature
IV. Fault Phenomenon - Cause - Solution Summary Table
| Fault Phenomenon | Possible Causes | Troubleshooting and Solutions |
|---|---|---|
| No system pressure / Weak action | 1. Relief valve set pressure too low or stuck2. Serious wear of hydraulic pump, large internal leakage3. Too low oil tank level, suction empty | 1. Check and adjust relief valve pressure2. Test pump volumetric efficiency, replace if necessary3. Replenish oil to standard level |
| Excessively high oil temperature (>82°C) | 1. Cooler blocked or fan fault2. Hydraulic oil viscosity too high or too low3. Serious system internal leakage | 1. Clean cooler, check fan2. Replace hydraulic oil meeting viscosity standard3. Check internal leakage of pumps, motors and valve groups |
| High hydraulic pump noise / Cavitation | 1. Oil suction filter blocked2. Air leakage in oil suction pipeline3. Excessively high oil viscosity | 1. Clean or replace oil suction filter element2. Tighten joints, replace seals3. Preheat oil or idle for temperature rise |
| Actuator crawling / Jitter | 1. Air mixed in the system2. Damaged hydraulic cylinder seal3. Poor lubrication of guide rails or pin shafts | 1. Open vent valve to exhaust air2. Replace hydraulic cylinder seal ring3. Check mechanical resistance, add grease |
| Oil emulsification (white / cloudy) | 1. Internal leakage of cooler (water enters oil circuit)2. Water vapor enters through oil tank breathing hole | 1. Check cooler seal, replace if necessary2. Replace hydraulic oil, clean oil tank |
V. Suggestions and Precautions
1. Oil Mixing Prohibition
Strictly prohibit mixing oil products: Different brands and grades of hydraulic oil have different additive components. Mixing may cause chemical reactions and produce sediments to block valve cores.
2. Thorough Oil Change
When replacing hydraulic oil, not only drain the oil in the oil tank, but also open the low-point valves of pipelines to drain residual oil in branches and components, and flush the system with new oil.
3. Hidden Fault Inspection
For hydraulic pipelines underwater (such as inside the cutter bridge), which are difficult to visually inspect, it is recommended to regularly check the pipe wall wear with an ultrasonic thickness gauge, or use ultraviolet dye with a black light to find tiny leaks.
4. Intelligent Maintenance
Modern advanced dredgers have begun to apply online monitoring systems to monitor the vibration of pumps and motors and oil cleanliness in real time. If your equipment is old, it is recommended to manually establish a detailed "maintenance ledger".
FAQ 1
Q: Why is the hydraulic system of a cutter suction dredger so important?
A: It drives key parts such as the cutter, positioning piles and winches. Its stability directly affects construction efficiency and safety.
FAQ 2
Q: What are the most common hydraulic faults on a cutter suction dredger?
A: Common faults include low pressure, slow movement, high oil temperature, abnormal noise, vibration, oil emulsification and oil leakage.
FAQ 3
Q: What is the key point of daily hydraulic maintenance?
A: Keep oil clean, maintain proper oil level and temperature, prevent air and water ingress, and replace filters and oil regularly.
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