As the core workhorse of port and waterway dredging operations, the operation efficiency and operational quality of Trailing Suction Hopper Dredgers (TSHDs) highly depend on the performance of full-set core dredging equipment, as well as the collaborative operation of leveling rake during the shallow sweeping phase.
This article systematically sorts out all core dredging equipment of TSHDs, focusing on the four key components: drag head, dredge pump, high-pressure water jet pump, and heave compensator, combined with other supporting core components and the operational technology of leveling rake for shallow sweeping, providing practical technical references for dredging engineering operations.
1. Core Dredging Equipment of TSHDs
1.1 Drag Head: The Core Soil Breaking Tool for Dredging Operations
The drag head is the soil breaking and suction device at the front end of the TSHD's pipeline, named for its shape similar to a nail rake, and it is the key component that determines dredging efficiency.
Development History: It has gone through four stages: erosion type, mechanical excavation type, excavation type with high-pressure water flushing system, and excavation type with high-pressure water flushing + double rake teeth, adapting to different soil operation requirements.
Structure Composition: It consists of a fixed body (high-pressure water tank, wear-resistant blocks, high-pressure nozzles, anti-collision frame, etc.) and a movable cover (rake tooth frame, rake teeth, grille, baffle, etc.).
Rake Tooth Selection:
Wide teeth: Suitable for organic soil, peat, silt, medium sand;
Narrow teeth: Suitable for silt, fine sand, gravel soil;
Double plow-shaped teeth: Suitable for cohesive soil.
Operation & Maintenance Focus: Key inspections include grille deformation and wear, side baffle cracks, nozzle aperture enlargement, rake tooth wear, flushing casing damage, and the integrity of the tooth seat protection sleeve.
Drag Head:
1.2 Dredge Pump: The Core Power Source for Slurry Transportation
The dredge pump is the core power component of the entire TSHD dredging system, which is custom-built for dredging operations . It is responsible for sucking the broken soil from the drag head, transporting the slurry through the pipeline to the hopper, and also providing power for the bow discharging and rainbowing system during unloading.
Type Classification: It includes onboard dredge pumps and integrated submersible dredge pumps, the latter of which can save deck space and reduce the load on the gantry and winch.
Operation Focus: It needs to adapt to high-concentration slurry transportation, and the wear-resistant design of the impeller and pump casing is the core of maintenance.
1.3 High-pressure Water Jet Pump: Auxiliary Breaking Power for Hard Soil
The high-pressure water jet pump is the core matching equipment for the drag head, which provides high-pressure water flow to the nozzles on the drag head. It can loosen hard soil such as clay and compacted sand, assist the drag head in breaking soil, and improve the suction efficiency of the drag head.
Working Principle: It generates high-pressure water flow, which is sprayed to the seabed through the nozzles on the drag head, breaking the compacted soil structure and mixing it with water to form slurry that is easy to suck.
Parameter Matching: The pressure and flow of the water pump need to be matched with the type of drag head and soil conditions to ensure the best soil breaking effect.
1.4 Heave Compensator (Swell Compensator): Posture Stabilization Component for Rough Sea
The heave compensator (also known as swell compensator in the industry) is the core component to ensure the stability of the drag arm in waves. It can buffer the heave movement of the ship caused by waves, ensure that the drag head always fits the seabed stably, avoid the drag head from hitting the seabed or leaving the seabed, and improve the operation stability and efficiency.
Working Principle: It uses hydraulic or spring structure to buffer the relative movement between the ship and the drag arm, isolating the wave impact from the drag head.
Application Scenario: It is particularly important for offshore dredging operations, which can ensure that the TSHD can still operate normally in rough sea conditions.
1.5 Drag Arm: Key Component for Slurry Transportation and Posture Adaptation
The drag arm (trailing suction pipe) is the transmission pipeline connecting the drag head and the hopper, whose core function is to transport slurry, while ensuring the drag head fits closely to the riverbed.
Core Performance: It has excellent flexural performance, which can still form a closed cavity when the riverbed undulates and the drag head rotates, ensuring suction efficiency.
Key Components: It includes sliders, elbows, one-piece joints, rubber suction hoses, cross joints, rotating pipes, gate valves & butterfly valves, etc. Among them, the cross joint realizes universal rotation, the rubber hose relieves swing torque, and the valves are used to control the flow of slurry.
Additional Functions: It can transmit data such as drag head dredging time to the hull, realizing operation status monitoring.
trailing suction pipe： 
1.6 Hopper: The Core Storage Unit for Dredged Material
The hopper is the core storage unit of the TSHD, which is used to store the dredged slurry and sediment during the dredging operation. After the hopper is full, the TSHD sails to the disposal area or unloading point to unload the material.
Structure Design: It is equipped with a bottom door for dumping material, and a flushing system to assist in unloading.
Capacity Classification: TSHDs are classified by hopper capacity, from small inland type to large mega type with over 40,000 m³ capacity.
1.7 A-Frame Hoist: The Support Mechanism for Drag Arm Retraction
The A-frame hoist is used for the in-outboard translation and storage of the drag arm, optimizing deck space utilization.
Structure Composition: It consists of a fixed body, A-frame, hydraulic cylinder, and drag arm rest, and the hydraulic cylinder drives the A-frame to retract and release.
Configuration Form: A single drag arm is equipped with a drag head hoist, intermediate pipe hoist, and elbow hoist. New TSHDs have optimized the intermediate pipe hoist and drag head hoist into an integrated one, simplifying the structure and facilitating maintenance.
1.8 Dredging Winch: The Core for Real-time Adjustment of Drag Arm Posture
The dredging winch is the most frequently operated equipment in dredging operations, which is a custom-built component exclusive to TSHD dredging systems. It adjusts the underwater posture of the drag arm through the retraction of steel wire ropes, ensuring the drag head works close to the seabed.
Working Principle: Driven by hydraulic/electric power, the steel wire rope drum is connected to the drag arm lifting plate through the guide pulley, realizing lifting and posture adjustment.
Lifting Capacity: The rated lifting capacity is calculated based on the total weight of the empty drag arm, high-pressure flushing pipe, and drag head combined with pulley efficiency; the maximum lifting capacity needs to be multiplied by a coefficient: 1.3 for the drag head winch, 1.5 for the intermediate pipe winch, and 2.1 for the elbow winch. The intermediate pipe winch also needs to additionally consider the load condition after removing the drag head.
1.9 Overflow System: Slurry Separation Component for Loading
The adjustable overflow system (overflow cylinder) is the core component during the loading phase of TSHD. It can discharge the excess water from the hopper, increase the solid concentration of the material in the hopper, and improve the loading efficiency of the hopper.
Working Principle: During the loading process, the slurry enters the hopper, the sediment settles, and the excess clear water is discharged through the overflow cylinder, which can adjust the overflow height to control the loading speed.
1.10 Bow Discharging & Rainbowing System: Efficient Unloading Components
The bow discharging and rainbowing system is the core unloading equipment of modern TSHDs, which can realize efficient unloading without sailing to the deep water disposal area.
Bow Discharging: It uses the dredge pump to transport the dredged material to the shore through the pipeline connected to the bow, which is used for land reclamation and beach nourishment.
Rainbowing (Bow Spraying): It sprays the dredged material to the designated area through the nozzle on the bow, which is used for shallow water filling and nearby disposal.
2. Leveling Rake: Core Dredging Equipment for Channel Shallow Sweeping
Independent shallow sweeping by TSHDs often leads to problems such as seabed furrows and mounds, which cause drag head sliding and reduce operational efficiency. Leveling rake can effectively solve these problems, improving the hit rate of shallow sweeping and operational efficiency.
2.1 Working Principle
The leveling rake is a rigid truss structure, towed by a tugboat for operation. It controls the lowering depth through vertical lifting steel wires, and the front pulling steel wires provide horizontal power. Relying on its own weight and structure to break soil, it realizes the "cutting peaks and filling valleys" to level the seabed. Its width can reach more than 12 meters, adapting to large-area channel shallow sweeping.
2.2 Key Operational Application Points
Personnel Configuration: A single leveling rake is equipped with 3 operation personnel, working in 24-hour rotation, recording operational parameters and tide levels, drawing shallow point block maps and navigation lines to guide the ship's routing.
Operational Control
Lowering Depth: Comprehensively determined based on tide level and shallow point elevation, and the steel wire rope is marked with scales for precise adjustment;
Operational Routing: Mainly based on string point operation, optimizing the curvature of the navigation line to adapt to the ship's handling capacity;
Steering Operation: The leveling rake must be lifted when steering to avoid cable friction interference.
Operational Specifications
Speed Control: The tugboat speed is controlled at 2-4 knots, low speed for flat tooth bulldozer type, and high speed for shovel type;
Working Condition Adaptation: Layered operation in areas with poor flatness, and priority transverse operation in areas with seabed furrows;
Steel Wire Length: Calculate the length of the front pulling steel wire according to the water depth to ensure the smooth posture of the leveling rake.
3. Technical Summary
The core dredging equipment of TSHDs, including the four key components drag head, dredge pump, high-pressure water jet pump, and heave compensator, as well as other supporting core components such as drag arm, hopper, A-frame hoist, dredging winch, overflow system, and bow discharging system, work together to complete the whole process of soil breaking, suction, transportation, storage, and unloading, which is the basic guarantee for dredging operations.
As another core dredging equipment for shallow sweeping, the leveling rake specifically solves the traditional operational problems of "seabed furrows" and "drag head sliding", greatly improving the efficiency and quality of channel leveling. The combination of the two can adapt to various soil conditions such as silt, sand, and clay, meeting the requirements of efficient and precise operation of port and waterway dredging operations.
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