Automated Mooring System Product

Overview

The automated mooring system (AMS) represents a paradigm shift in port efficiency and safety. Traditional mooring requires a ship's crew to manually throw heaving lines to shore workers, who then guide heavy mooring ropes through fairleads and secure them to bollards. This labor-intensive, hazardous process exposes workers to crushing forces (mooring lines can break under 500+ kN tension, creating lethal whip hazards) and depends on skilled personnel availability.

The AMS eliminates manual rope handling: a quayside robotic arm with vacuum suction pads automatically engages ropes fed from the vessel, guides them through shore-mounted guide rails, and secures them—all under PLC automation with remote operator control. Modern AMS installations can moor a large container ship (20,000+ TEU) in 10–15 minutes, compared to 30–45 minutes with traditional methods.

How It Works

A vessel approaches the quay and comes to a stop at berth. The ship's mooring party feeds the first mooring line (a heavy synthetic rope, typically 40–80mm diameter) overboard, where it hangs from the ship's fairlead (a reinforced eyebolt on the hull). The line drops toward the quay.

The AMS operator (stationed in the Shore Control Station booth on the quay) watches the line fall. Using the Joystick Pendant, the operator commands the Articulated Arm to move: the Shoulder Joint (a large hydraulic cylinder driven by the Hydraulic Power Unit) swings the arm toward the falling rope, and the Elbow Joint bends to position the Vacuum Pad Assembly (four or more suction pads) over the rope.

The Vacuum Pump (housed in the hydraulic power unit) draws air, creating a 0.5–0.8 bar vacuum (below atmospheric pressure). This differential pressure sucks the rope against the Vacuum Pad Cup surface with a grip force of 30–80 kN per pad. The Pad Check Valve maintains vacuum even as the rope moves.

Once the rope is gripped, the PLC Control System takes control of arm motion, guiding the rope along the Rope Guide Rails—a pair of steel channel rails with low-friction rollers. As the rope is drawn across these rails, the Load Cell integrated into the rail assembly measures tension in real-time, feeding data to the Tension Display in the control booth.

The arm guides the rope toward a bollard or tensioning winch on the quay. As the ship's winch or shore winch applies tension, the rope tension rises. The Tension Monitoring System system continuously monitors load; if tension exceeds a preset safe limit (typically 500–1000 kN depending on rope strength), the Over-Tension Alarm Solenoid triggers, and the Release Solenoid immediately vents the vacuum from all pads.

Within 1–2 seconds, the pads release their grip, and the rope is handed off to shore personnel or a tensioning winch for final securing. The arm retracts to home position, and the operator engages the next rope. With 4–6 mooring lines (typical for a large ship), the entire mooring sequence takes 10–20 minutes.

If an emergency occurs (e.g., rope breakage, system malfunction), the operator presses the Emergency Stop Button in the control booth, de-energizing all solenoids immediately. The Release Accumulator, which stores pressurized air, automatically vents vacuum from the pads, releasing the rope.

Subsystems

Pedestal and Structural Base

The Pedestal Frame is a rigid steel structure welded to the quay deck. The Frame Columns (four corner posts, 30–40cm diameter steel tube) form the primary support. The Frame Cross-Beams (horizontal I-beams) brace the columns laterally and provide mounting bosses for the articulated arm. The Foundation Plate is a large steel plate bolted to the quay with multiple anchor bolts rated for the combined moment loads from rope tension and arm articulation.

The Arm Pivot Bearing is a roller or ball bearing supporting the base of the articulated arm, allowing the arm to swing ±45 degrees in the horizontal plane for positioning over different fairleads on the ship or different bollards on the quay.

Articulated Arm

The Articulated Arm is a two-joint robotic arm: the Shoulder Joint (large hydraulic cylinder, bore 10–15cm) rotates the entire arm at its base. The Upper Boom Section extends from the shoulder, and the Elbow Joint (smaller cylinder, bore 8–12cm) bends the arm midway. The Lower Boom Section extends from the elbow, and the Wrist Coupling at the tip accepts the Vacuum Pad Assembly.

Each joint is powered by a dedicated proportional spool valve in the Solenoid Manifold, allowing the operator to move the arm fluidly with proportional joystick input. The Position Sensor on each joint (potentiometer or encoder) feeds arm angle back to the PLC Controller, which uses this feedback to prevent collisions with the ship, bollards, or other obstacles, and to auto-position the arm for optimal rope capture.

Vacuum Pad Assembly

The Vacuum Pad Assembly (typically 4–6 units mounted in a cluster at the arm tip) is the rope-gripping mechanism. Each pad comprises:

• The Vacuum Pad Cup: A flat or slightly domed elastomer cup (25–40cm diameter) with a textured surface in contact with the rope. The cup shape and texture maximize grip without rope slipping.
• The Pad Check Valve: A spring-loaded check valve maintaining vacuum in the cup as the rope moves, even if ambient pressure tries to equalize the chamber.
• The Pad Actuator Solenoid: A solenoid valve venting the cup to atmosphere when de-energized, releasing the rope.

Vacuum (0.5–0.8 bar below atmospheric) is generated by the Vacuum Pump in the hydraulic power unit, piped through flexible hoses to each pad. Grip force per pad is 30–80 kN, depending on pad diameter and vacuum level. A four-pad cluster can develop total grip force of 120–320 kN, easily handling ropes and synthetic fiber lines of 40–80mm diameter.

Hydraulic Power Unit

The Hydraulic Power Unit is a self-contained module integrating all power generation. The Electric Motor (40–75 kW, 400V 3-phase) is the primary power source, chosen over diesel for environmental reasons and port regulations. The motor shaft drives both:

1. The Hydraulic Pump: A variable-displacement pump (50–100 LPM at nominal pressure) supplying high pressure (280 bar) oil to the arm cylinders via the proportional valve manifold.

2. The Vacuum Pump: A rotary vane or screw-type pump generating continuous vacuum (0.5–0.8 bar below atmospheric) for the suction pads.

The Hydraulic Reservoir (500–1000 liters) provides fluid storage with integral baffles, return filtration (Return Filter, 10-micron), suction strainer, and cooling. The Pressure Relief Valve (pilot-operated, set at 280 bar) protects the system from overpressure if cylinders encounter resistance.

Control System

The Control System is the brain of the AMS. The PLC Controller (industrial-grade, hardened for marine environment) runs the mooring sequence logic:

1. Ready state: Waiting for operator command to begin mooring.
2. Arm positioning: Move arm to intercept falling rope, using feedback from Position Sensor.
3. Rope engagement: Activate vacuum when rope enters pad zone.
4. Tension monitoring: Read Load Cell tension as rope is drawn across guide rails.
5. Tension control: If tension exceeds limit, trigger release solenoid.
6. Release: Vent vacuum and retract arm to home position.

The Solenoid Manifold executes proportional valve commands from the PLC, modulating arm motion smoothly. The Pressure Transducer (3 units) monitor hydraulic circuit pressures and vacuum chamber pressure, alerting the controller to abnormal conditions. The Load Cell integrated into the rope guide rail measures tension continuously.

The Safety Interlock Relay is a hardwired safety relay that enforces emergency stop logic: if the operator presses the Emergency Stop Button, the relay immediately de-energizes the proportional valve solenoids and the release solenoid, bringing the system to a safe state within milliseconds. This hardwired logic is independent of the PLC, ensuring safety even if the PLC malfunctions.

Rope Guide Rails

The Rope Guide Rails are steel channel or V-groove rails (20–30cm height) guiding the rope from the ship fairlead to the bollard or shore winch. The Guide Rail Rollers (six or more, 8–12cm diameter, ball-bearing type) support the rope and reduce friction, allowing smooth rope flow even under 500+ kN tension.

The Rope Guide Tension Sensor, a load cell integrated into the guide rail bearing block, measures rope tension as the line passes. This sensor feeds real-time tension data to the shore control station display, allowing the operator and ship's officer to monitor load and coordinate tensioning operations.

Tension Monitoring

The Tension Monitoring System system ensures safe rope handling. The Load Cell is the primary sensor, measuring rope tension in real-time. The Tension Display (digital display in the control booth) shows tension in kN or tonnes. The Data Logger records the mooring sequence timeline: when rope was engaged, tension history, when released, etc., providing a detailed log for auditing and incident investigation.

The Over-Tension Alarm Solenoid is a failsafe: if rope tension exceeds a preset limit (typically 500–1000 kN, depending on rope strength and safety margin), the solenoid valve triggers, venting vacuum and releasing the rope. This prevents rope breakage and the resulting whip hazard.

Emergency Release

The Emergency Release System provides multiple layers of failsafe:

1. The Release Solenoid: Normally energized, holding vacuum on the pads. If de-energized, it vents vacuum within 0.5 seconds.

2. The Manual Release Valve: A manual ball valve that deck crew can turn to manually vent vacuum and release the rope in case of power loss or system failure.

3. The Release Accumulator: A nitrogen-charged bladder accumulator storing compressed air at 60–80 bar. If power is lost and the electric vacuum pump stops, the accumulator supplies air to vent the vacuum pads, releasing the rope automatically.

4. The Failsafe Pressure Switch: An electronic switch detecting loss of system pressure; if pressure drops below a threshold, it triggers the release solenoid.

Shore Control Station

The Shore Control Station is the operator's command center. The Control Booth is a weather-resistant aluminum or stainless steel shelter positioned with clear sightlines to the ship and quay. Inside:

• The Joystick Pendant: A proportional joystick controller (wireless or hardwired) with independent X-Y axes controlling arm shoulder and elbow movements.
• The Tension Display Panel: Displays real-time rope tension in kN or tonnes, allowing the operator to coordinate with ship and shore winch personnel.
• The Sequence Status Display: LED indicators showing system state (ready, rope engaged, under tension, idle, error).
• The Emergency Stop Button: A large red 60mm pushbutton hardwired directly to the safety relay, bypassing the PLC for instantaneous stop.
• The Audio Alarm System: A loud sounder (95+ dB) alerting operators to error conditions or excessive rope tension.

Performance and Operational Characteristics

Modern AMS installations can moor a large container ship in 10–15 minutes (4–6 ropes at 2–4 minutes per rope), compared to 30–45 minutes with traditional manual methods. The reduction in labor (no shore linesmen needed for heavy rope handling), elimination of injury risk (no whip hazard, no manual lifting), and increased safety (automated tension control, emergency release) justify the capital investment.

Power consumption is modest: the 40–75 kW electric motor runs intermittently (5–15 minutes per mooring operation) and at variable load. A typical mooring operation consumes 3–8 kWh.

Maintenance is straightforward: hydraulic fluid sampling annually, oil changes every 2–3 years, hose inspections every 6 months, and load cell calibration annually. Rope guide rails are inspected regularly for wear; rollers are replaced if damage is observed. Vacuum pump service includes filter replacement annually and internal seal kit replacement every 3–5 years.

Safety standards are strict. IMO SOLAS, IEC 61508 (functional safety), and IMCA (International Maritime Contractors Association) guidelines govern AMS design. Modern systems are certified to meet dynamic positioning (DP) vessel requirements, ensuring compatibility with DP-capable ships that require precise tension and timing during mooring.

Environmental benefits include reduced engine noise (electric vs. diesel), lower emissions, and improved worker safety (zero manual rope handling exposure). Port authorities increasingly mandate AMS on major quays to streamline operations and improve safety culture.

Rope dynamics are carefully managed: the PLC ramps tension gradually, preventing shock loads that would damage the rope, ship, or quay structure. Coordination with the ship's deck and engine control room is essential; modern AMS systems integrate with the ship's mooring management system via VHF or dedicated communication links, enabling synchronized operations without verbal miscommunication.