Marine Mooring Equipment and Winches

Background

Mooring equipment functions

Mooring equipment serves multiple functions:

• Berthing: securing the ship at a port berth against wind, current, tide.
• Single buoy mooring (SBM): securing the ship to a single mooring buoy at offshore terminals.
• Ship-to-ship (STS) transfer: secure mooring between two ships during cargo transfer at sea.
• Anchoring assistance: deploying and recovering anchor.
• Towing: connection point for tow lines.
• Hawser handling: managing tow connections.
• Cargo handling assist: in some configurations supporting cargo operations.

The mooring system is operationally critical (ship cannot operate without it) and safety-critical (mooring incidents have caused fatalities).

Major manufacturers

Marine mooring equipment manufacturers:

• MacGregor (Cargotec): extensive product range from cargo to mooring.
• Rolls-Royce/Kongsberg: legacy Rolls-Royce mooring winches, Hatlapa heritage.
• Pusnes (now part of MacGregor): high-end winch supplier.
• DMW (Diving Mechanical Workshop): specialist supplier.
• TTS Marine: deck machinery including winches.
• Various Korean and Chinese builders: domestic and export market.

The market consolidation has produced a small number of major suppliers servicing global newbuild market.

Winch types

Split-drum mooring winch

Split-drum (also called multi-drum):

• Storage drum: holds the bulk of the mooring rope.
• Tension drum: smaller drum where the rope is engaged when in use.
• Operation: rope paid out from storage drum, transferred to tension drum, with brake holding tension.
• Advantages: clear separation between storage and operational use; reduced rope wear during storage.
• Application: standard for medium and large ships.

Traction winch

Traction winch (also called constant-tension):

• Continuous tension: maintains preset tension on the rope.
• Operation: the winch automatically pays out rope as load increases or hauls in as load decreases.
• Application: smaller ships, special applications.
• Advantages: maintains tension automatically against tide and wind variation.

Self-tensioning winch

Self-tensioning:

• Automatic adjustment: maintains tension within preset range.
• Programmable: bridge can set target tension and limits.
• Modern: electric variable-speed drive with intelligent control.

Combination winch

Combination winches:

• Mooring plus capstan: combining functions in single unit.
• Mooring plus anchor: combining mooring and anchor handling.
• Cost-effective: for smaller vessels.

Capstans

Capstans:

• Vertical-axis winch: with rope wrapped around vertical drum (mooring head).
• Operation: rope pulled by hand or by wrapping around the head with friction.
• Use: smaller vessels, smaller mooring lines, or where space is limited.
• Drive: electric or hydraulic.

Fairleads and chocks

Roller fairleads

Roller fairleads:

• Function: redirecting mooring rope over the ship’s side without chafing.
• Type: rotating roller in cradle.
• Material: cast steel, hardened.
• Position: at strategic points for the mooring layout.

Panama chocks

Panama chocks (also called closed chocks):

• Function: feed-through for mooring rope through the bulwark.
• Type: cast or welded with rounded internal surfaces.
• Standard: closed type allows rope to pass through without escape.
• Position: matched to bollard locations onshore.

The Panama Canal originally specified the geometry; the standard is now used globally.

Bollards and bitts

Bollards (single or double):

• Function: shipside attachment point for mooring rope.
• Configuration: single or double cylindrical post on a base.
• Material: cast steel.
• Standard sizing: by SWL (safe working load) per ship size.

Mooring rope and wire

Rope materials

Mooring rope materials:

• Synthetic rope: most common modern type. Materials include:
  • Polyester: traditional, moderate strength, moderate elasticity.
  • HMPE (Dyneema, Spectra): very high strength, very low elasticity, lightweight.
  • Nylon: high elasticity (good for shock absorption), but creep issues.
• Wire rope: traditionally used for high-strength applications.
• Combination wire/synthetic: wire main rope with synthetic tail for elasticity.

The trend is toward HMPE due to weight (handling safer) and strength characteristics.

Rope inspection and replacement

Rope inspection:

• Visual inspection at every use.
• Detailed inspection periodically, looking for:
  • Cuts, abrasion, broken yarns.
  • Inconsistent diameter.
  • Localised wear.
  • UV damage.
  • Chemical contamination.
• Strength testing when inspections indicate degradation.
• Replacement based on condition rather than time alone.

OCIMF MEG4 provides industry-standard rope management guidelines.

OCIMF MEG4 mooring forces

Mooring force calculation

Mooring forces are calculated under OCIMF MEG4:

• Wind force: based on ship windage area, exposure, wind velocity profile.
• Current force: based on ship submerged area, current velocity profile.
• Wave force: based on swell and chop conditions.
• Surge and sway: dynamic motion adding to peak force.

The calculation produces total transverse and longitudinal forces, with the mooring layout designed to provide the required restraint.

Mooring layout

Standard mooring layout (typical for tankers and cargo ships):

• Head lines: forward, restraining astern motion.
• Stern lines: aft, restraining ahead motion.
• Breast lines: perpendicular to the ship, restraining transverse motion.
• Spring lines: at angle, restraining both ahead and astern motion.

Total typically 10 to 16 lines for moderate-sized ships, more for very large ships.

Specific mooring layouts

Specific applications:

• Standard berth: ship alongside dock, 10-16 lines, mix of head, stern, breast, spring.
• SBM (Single Buoy Mooring): ship moored to floating buoy by single hawser.
• STS (Ship-to-Ship): two ships moored side-by-side with multiple lines.
• Floating production: as on FPSO units, with permanent or removable mooring.

Winch operations

Heaving and paying out

Heaving (pulling in):

• Engagement: line engaged on winch tension drum.
• Heaving operation: winch hauls in line under power.
• Brake control: operator monitors tension and uses brake to maintain control.
• Storage: hauled-in line stored on storage drum if split-drum type.

Paying out:

• Brake release: line allowed to run out under controlled tension.
• Brake control: maintaining safe pay-out rate.
• Termination: line tensioned at brake when target reached.

Tension control

Tension control during operations:

• Manual tension: operator manages brake to maintain target tension.
• Self-tensioning mode: winch automatically maintains preset tension.
• Tension monitoring: sensors providing feedback.
• Alarm thresholds: at high tension warning operator.

Multiple winch coordination

Multiple winches:

• Coordinated operation: across forward and aft mooring decks.
• Bridge command: operator coordinates from bridge or from mooring station.
• Communication: between mooring station crews and bridge.
• Documentation: of mooring operation.

Safety considerations

Snapback zones

Snapback (recoil from broken mooring line) is the principal serious safety concern:

• Snapback zone: area of the deck where a broken line might whip after release.
• Protective measures: keep crew clear of snapback zones during operations.
• Marking: lines and zones marked on deck.
• Training: crew familiar with snapback risks.

Common mooring incidents

Common mooring incidents:

• Broken lines causing recoil/snapback: with potential fatal injury.
• Crew caught in winch drum: typically during hauling operations.
• Falls from height: during inspection or maintenance.
• Crushing injuries: between line and bollard or fairlead.
• Dropped objects: from winch or rope handling.

Annual industry mooring fatalities globally are 5-15, with serious injuries 10x more frequent.

Safety procedures

Safety procedures:

• Mooring station planning: identifying hazard zones.
• Pre-operation briefing: covering specific risks for the operation.
• PPE: appropriate clothing, gloves, hard hat, safety glasses.
• Communication: clear signals between mooring crew and bridge/stations.
• Emergency procedures: in case of line failure or other event.
• Watchkeeping: dedicated crew during entire mooring operation.

Training under STCW

Training under STCW:

• STCW Section A-II/4: ratings forming part of a navigational watch.
• STCW Section A-VI/1: basic safety training.
• Operator-specific training: on the actual mooring equipment installed.

Specific applications

Tanker mooring

Tanker mooring:

• High-load mooring: large ship windage and current exposure.
• Multi-line layout: typically 12-16 lines for VLCC.
• Standardised tanker mooring: matching shore facilities globally.
• Quick-release hooks: at terminal for rapid disconnect in emergency.

Container ship mooring

Container ship mooring:

• High windage: from container stack.
• Limited mooring deck space: at extreme bow and stern.
• Standardised mooring layout: per OCIMF MEG4.

Cruise ship mooring

Cruise ship mooring:

• Very large ships: requiring high-capacity winches.
• Frequent port calls: high mooring activity.
• Passenger sensitivity: minimising noise during mooring operations.
• Rapid manoeuvring: at busy cruise ports.

Bulk carrier mooring

Bulk carrier mooring:

• Heavy ships when laden: deep draught creates significant windage with deck cargo.
• Standard mooring layout.
• Cargo operation considerations: mooring during loading affects ballast adjustment.

Offshore vessel mooring

Offshore vessel mooring:

• DP (Dynamic Positioning) when working at offshore installations: mooring not used.
• Conventional mooring at port.
• Anchor handling as primary function for AHTS vessels.

Maintenance

Routine maintenance

Routine maintenance:

• Daily: visual inspection of winches and ropes.
• Weekly: more detailed inspection.
• Monthly: brake testing.
• Quarterly: detailed examination including lubrication.
• Annual: comprehensive inspection.

Class society oversight

Class society oversight:

• Initial certification at ship delivery.
• Annual surveys: visual examination.
• Internal examination: at periodic surveys.
• Brake testing: under load periodically.

Common maintenance issues

Common maintenance issues:

• Brake degradation: requiring adjustment or replacement.
• Hydraulic system leaks: in electrohydraulic winches.
• Electrical motor wear: in all-electric winches.
• Drum bearing wear: from heavy-load operations.
• Rope chafing on fairleads: from misalignment.

Future developments

Automation

Automation in mooring:

• Automatic mooring systems: vacuum-pad or magnet-based automatic mooring at port.
• Reduced crew need: through automation.
• Quick connection/disconnection: improving port turnaround.

Decarbonisation

Decarbonisation:

• All-electric winches: replacing electrohydraulic for efficiency and emissions.
• Battery-driven winches: with peak load smoothing.
• Energy recovery: from winch braking.

Enhanced safety

Enhanced safety through:

• Improved snapback indicators: dynamic visualisation of risk zones.
• Real-time tension monitoring: with predictive alerts.
• Enhanced training: through simulation.
• Better PPE: with improved abrasion and impact resistance.

See also

• Mooring Forces and Station Keeping
• Marine Steering Gear
• Marine Auxiliary Engines and Generators
• Oil Tanker
• Container Ship
• STCW Convention
• SOLAS Chapter II-1: Construction, Subdivision, Stability, Machinery and Electrical Installations

References

• OCIMF MEG4 Mooring Equipment Guidelines, 4th edition.
• IACS Common Structural Rules.
• Class society marine deck machinery rules.
• IMO MSC.1/Circ.1175 on mooring system design and operation.
• Port and terminal operator standards.