Net Drum Product

Overview

A net drum reel is a large-diameter powered spool used on commercial fishing vessels to store, deploy, and retrieve trawl nets, seine nets, or gillnet systems. The reel consists of a main cast-iron or steel barrel (1.2–2.0 m outer diameter, 0.8–1.5 m face width) mounted on a sturdy shaft, driven by a 20–40 hp bent-axis or radial-piston Hydraulic Motor. The entire assembly sits on a structural steel Frame Assembly anchored to the vessel's deck.

Unlike dedicated fishing winches (Trawl Winch, Mainline Reel), the net drum is designed for lower-speed, high-torque spooling of the entire trawl net itself (not the warp lines). A vessel typically carries one or two net drums for rapid turnaround: while one net is being hauled and processed, crew can manually unspool the next net from a second drum, pre-rig it with warps and bridles, and be ready to deploy within 30–60 minutes of catch completion.

The Level-Wind Mechanism mechanism reciprocates horizontally as the drum rotates, packing net evenly across the face width and preventing rope jam or uneven load. A spring-set Brake Unit, backed by an accumulator, holds the drum stationary when the Hydraulic Motor is off, preventing uncontrolled spill in rough seas. All hydraulic components are cooled via seawater circulation through a Oil Cooler, and control is via a sealed proportional joystick pendant.

How It Works

Net stowage and preparation: Following haul and catch processing, the empty trawl net (now 500–2000 m of mesh, warps, and bridles) is manually gathered and fed into the net drum. As the crew feeds net into the drum, the operator engages the motor at slow speed (10–20% joystick deflection), spooling net onto the barrel. The Level-Wind Mechanism carriage reciprocates across the drum face, distributing net evenly and preventing localized overload or jamming. The process takes 30–60 minutes for a large trawl.

Once fully spooled, the Brake Unit is engaged (brake applies automatically when motor is stopped), and the net is lashed or secured to the drum with spare rope to prevent unspooling in heavy weather.

Deployment sequence: For the next haul, crew unlock securing lines and begin feeding the net bridles toward the stern. The operator engages the motor in reverse at slow speed, allowing net to unspool smoothly. The Level-Wind Mechanism mechanism reciprocates in sync with drum rotation, ensuring even payout across the entire net length. The bridled net trails behind the vessel as it approaches the fishing ground. Once the entire net is deployed (full spool length), the operator disengages the motor and applies the brake.

Load management: The Hydraulic Motor is controlled via a proportional Control Valve with joystick input. The valve integrates Load Sensor feedback (pressure on motor pilot line), allowing the operator to feel resistance and adjust speed proportionally. If net suddenly hangs on an obstacle, load increases automatically, and the operator can ease off the joystick to prevent motor stall or hose rupture. A load-limiting relief valve (typically 200 bar in the motor circuit) protects the system.

Hydraulic circulation: The net drum is powered via a hydraulic pump (usually shared with the Trawl Winch or main fishing winch) fed by the vessel's auxiliary diesel engine. Oil is routed through the Control Valve, which directs flow to the Hydraulic Motor at variable displacement. Return oil (now warm from motor friction losses) flows through the Oil Cooler, where raw seawater absorbs heat, then back to the ship's hydraulic reservoir. The Brake Accumulator (5 L, 100 bar pre-charge) supplies pilot pressure to release the brake, allowing smooth engagement and disengagement.

Typical Net Drum Installation

• Vessel class: Stern trawler, seine netter, or gillnetter, 20–80 m
• Net drums onboard: 1–2 (larger vessels typically 2 for continuous operations)
• Net type: Bottom trawl, midwater trawl, or purse seine
• Hydraulic power source: 60–100 hp auxiliary diesel, shared with main fishing winch
• Crew for deployment: 2–3 deck hands manually feeding net, operator controlling motor from pendant
• Cycle time: 20 min unspool + 45 min haul + 30 min respool = 95 min per fishing cycle

Design Variations

High-capacity variant: Larger drum (1.8–2.0 m OD), 1.5 m face width, capacity 1500–2000 m, 40 hp motor; typically on large trawlers or pelagic purse seiners.

Compact variant: 1.2 m OD, 0.8 m width, capacity 500 m, 20 hp motor; found on small coastal trawlers or gillnetters.

Carrousel net drum: Some modern vessels use a rotating carousel rather than a fixed drum, allowing simultaneous respool of one net and unspool of another. Adds mechanical complexity but dramatically increases fishing efficiency.

Manual backup: On smaller vessels without hydraulic net drums, crew manually unspool net over stern rollers or davits—labor-intensive but eliminates motor dependency.

Maintenance Schedule

• Weekly: Check brake accumulator pressure (100 bar target) via gauge; verify motor coupling bolts for looseness.
• Monthly: Inspect Level-Wind Roller bearings; drain oil sample for analysis (viscosity, water content, wear debris).
• Quarterly: Flush Oil Cooler seawater side if plankton fouling suspected; replace suction strainer in hydraulic circuit.
• Annually: Full motor displacement calibration; brake friction-disc measurement; bearing seal replacement if oil leakage visible.

Operational Safety

Load limiting: Net drums are typically fitted with load-relief valves set to 200 bar, preventing catastrophic pressure if net jams or snarls.

Brake redundancy: The spring-set brake ensures the drum cannot freewheel even if hydraulic pressure is lost, critical in rough conditions.

Dead-man control: Joystick release immediately disengages motor and applies brake; operator cannot be forced into dangerous position.

Crew signaling: Standard hand signals between net master (at drum) and operator (at pendant) prevent miscommunication and entanglement hazards.

Integration with Other Systems

Modern net drums integrate with the main fishing winch (Trawl Winch) and may share the same hydraulic pump and control system. This allows simultaneous hauling (via winch) and respooling (via net drum)—an efficiency gain on large vessels. The Fish Hold Refrigeration system is entirely independent but shares the vessel's diesel generator for auxiliary power.