Common Faults and Troubleshooting of Trailing Suction Hopper Dredgers | Dredging Construction Maintenance

Trailing Suction Hopper Dredger: Common Faults and Troubleshooting

During dredging construction, equipment failures are inevitable and require on-site timely handling. The common faults and treatment suggestions are as follows:

1 Blockage of Drag Head, Suction Pipe and Sediment Box

1.1 Symptoms: Sudden increase or sustained high vacuum, unstable mud pump speed, reduced slurry flow or even cutoff, loud vibration in the mud pump and pipelines.

1.2 Solutions:

Caused by excessive penetration depth of the drag head or debris stuck at the suction inlet or pipeline.

1.2.1 Raise the drag head, reduce penetration depth or continue lifting to flush with clean water.

1.2.2 Adopt the “stop backflow method”: temporarily stop the mud pump and use backwater and potential energy in the suction pipe to flush out debris.1.2.3 Widen the grid spacing.1.2.4 Lift the drag head for manual removal.

2 Mud Pump Blockage

2.1 Symptoms: Low vacuum, low discharge pressure, abnormal vibration inside the pump.

2.2 Solutions: Caused by damaged suction grid, excessive grid spacing, or debris, sand or soil blocks sucked in.

2.2.1 Repair the grid and adjust spacing.

2.2.2 Flush with clean water.2.2.3 Start the pump for manual cleaning.

3 Discharge Pipeline Blockage

3.1 Symptoms: High discharge pressure, low vacuum, small flow or cutoff, slow mud pump speed or suction vacuum.

3.2 Solutions: Caused by excessively long pipeline during reclamation, head loss exceeding total pump head, excessively high slurry concentration, or debris stuck in the pipeline.

3.2.1 Flush with clean water.

3.2.2 Suddenly increase pump speed (not too long) to flush out blockages hydraulically.3.2.3 Manual removal.

4 Vessel Tilt During Discharging or Dumping

4.1 Symptoms: Vessel tilts left or right.

4.2 Solutions: Caused by blockage on one side of suction pipes in the hopper, unbalanced slurry suction on both sides, or unbalanced mud discharge during dumping.

4.2.1 Close the valve on the upward tilting side to stop suction, focus on suction on the downward side, and add clean water properly.

4.2.2 Flush water into the hopper from the discharge pipeline on the upward tilting side.4.2.3 When loading clay or sand, partially open the mud door first and fully open after reaching a proper level.

5 Vessel Tilt During Discharging or Dumping

5.1 Symptoms: Vessel tilts left or right.

5.2 Solutions: Same as Fault 4.

5.2.1 Close the valve on the upward tilting side to stop suction, focus on suction on the downward side, and add clean water properly.

5.2.2 Flush water into the hopper from the discharge pipeline on the upward tilting side.5.2.3 When loading clay or sand, partially open the mud door first and fully open after reaching a proper level.

6 Mud Door Leakage

6.1 Symptoms: Hopper cannot be fully loaded or leaks during sailing.

6.2 Solutions: Caused by debris jamming the mud door, damaged packing, or insufficient hydraulic pressure.

6.2.1 Underwater inspection and debris removal.

6.2.2 In areas with two soil types, dredge non-leaky soil first to bed the hopper bottom, then dredge leaky soil.6.2.3 Maintain required hydraulic pressure for closing the mud door.

7 Breakage of Drag Head Hoisting Cable

7.1 Symptoms: Slack cable without tension, top pulley moving upward, increased concentration.

7.2 Solutions: Caused by severe friction/corrosion or overload.

7.2.1 Maintain original course, proceed slowly against current; no reversing.

7.2.2 Raise the elbow and intermediate pipe.7.2.3 Lift the drag head with a safety cable; if unavailable, attach a cable from the elbow down to the drag head and tighten to lift.

8 Sand Pumping Channel Blockage

8.1 Symptoms: At the beginning of pipeline flushing, after opening the dilution valve, closing the overboard suction valve immediately causes sharp concentration rise and flow drop, lasting for a long time.

8.2 Solutions:

8.2.1 Observe sand deposition in the hopper; deep pits indicate the blockage location behind.

8.2.2 Partially close the overboard suction valve to keep concentration 1.2–1.3 t/m³ and velocity 5.0–6.0 m/s, then close the dilution valve.8.2.3 Use overboard suction as water diversion for reclamation before the blockage, open small mud doors timely, and activate high-pressure flushing to move sand forward for discharge.

9 Shore Pipeline Blockage

9.1 Symptoms: Gradual flow decrease and pressure rise during normal sand discharging; ineffective even after closing all small mud doors; low-pressure outflow and reduced flow at the reclamation outlet.

9.2 Solutions: Close all small mud doors, gradually close the dilution valve, slowly open the overboard suction valve to flush the blockage. Resume normal operation after flow velocity exceeds 7.0 m/s.

10 Sand Overflow

10.1 Symptoms: During informal sand pumping with channel blockage, sand reduces automatically without pumping when the dilution valve is open.

10.2 Solutions: Close the dilution valve immediately.

The above are common faults and treatment methods for trailing suction hopper dredgers in construction for reference.

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