Shark Jaw & Towing Pin Systems for Tugboats

Why Tugboats Need Shark Jaw Systems

Tugboat operations demand reliable, repeatable control over towing connections under dynamic load conditions. Whether manoeuvring a laden VLCC through a harbour channel or holding station during an offshore escort, the towing connection is the single most critical mechanical interface on the vessel.

Traditional manual towing hooks require crew to work in close proximity to the tow wire or chain under load — a significant safety hazard. A hydraulically operated shark jaw eliminates this risk by enabling the master to engage or release the towing connection remotely from the wheelhouse or a protected deck station. In an emergency, the wire or chain can be let go instantly without crew exposure.

Beyond safety, a properly specified shark jaw system provides:

• Consistent bite geometry — the jaw closes to a defined throat opening, preventing wire snatching and reducing shock loading on the connection
• Load monitoring integration — inline load cells paired with the hydraulic control circuit enable real-time bollard pull readout and overload alarm
• Reduced wear on tow wire — controlled engagement eliminates the sliding-bite damage common with hook-and-roller arrangements
• Regulatory compliance — major port authorities and classification societies increasingly specify or prefer shark jaw arrangements for new tug builds

Harbour Tug vs. Ocean-Going Tug Requirements

The operating profile of a harbour tug differs substantially from a deep-sea or ocean-going tug, and equipment specification must reflect this.

Harbour Tugs

Harbour tugs work in short, high-intensity cycles — berthing and unberthing large vessels, often in confined waterways where response time is critical. Key characteristics:

• Lower SWL range — typical harbour tug bollard pull of 25–80 MT means shark jaw systems in the SJ-50 to SJ-100 class are appropriate
• High cycle frequency — the jaw engages and releases dozens of times per day; hydraulic circuit design and seal specification must account for this duty cycle
• Compact deck footprint — harbour tugs have limited stern deck area; low-profile jaw bodies and integrated roller assemblies reduce the required installation envelope
• Fibre and steel wire handling — modern HMPE synthetic tow lines require jaw throat designs that avoid edge loading and fibre damage

Ocean-Going and Escort Tugs

Long-haul towing and open-ocean escort operations impose different demands:

• Higher SWL — coastal and ocean-going tugs with bollard pull of 80–250 MT require SJ-200 to SJ-300 class systems rated for sustained static and dynamic loads
• Chain handling capability — offshore towing frequently involves chain bridles and messenger lines; the jaw must accommodate stud-link chain in the relevant diameter range without re-rigging
• Severe weather performance — sustained open-ocean operations in Sea State 5–6 require hydraulic circuit accumulators to maintain jaw closure force under dynamic vessel motions
• Salvage tug requirements — salvage operations may require rapid equipment reconfiguration; combined shark jaw and towing pin arrangements allow switching between chain and wire in-service

Recommended Configurations

Selecting the correct model depends on the vessel’s bollard pull, the towing medium (wire, chain, or HMPE), and the classification society requirement.

Vessel Type	Typical Bollard Pull	Recommended Model	Notes
Harbour tug	25–60 MT	SJ-100	Compact jaw body, high cycle duty
Coastal/harbour tug	60–120 MT	SJ-100 / SJ-200	Wire or HMPE primary
Coastal tug	120–200 MT	SJ-200	Chain or wire capability
Ocean-going tug	200–300 MT	SJ-300	Accumulator-equipped HPU recommended
Deep-sea / salvage tug	300–400 MT	SJ-400	Full chain handling, remote load monitoring

For escort tug applications where the vessel must hold a defined heading load on a ship under way, a shark jaw and towing pin combo is strongly recommended. The towing pin controls the lateral position of the wire, reducing yawing loads on the jaw body and improving directional stability.

Installation Considerations

Stern Deck Space and Structural Integration

The shark jaw body must be mounted on a reinforced pad that transfers towing loads directly into the vessel’s main structural frames. Key points:

• Foundation sizing should be based on the jaw’s maximum static holding capacity (not the SWL), typically 1.5–2.0× SWL
• The jaw body centreline should align with the vessel’s towing centre point (typically slightly above and aft of the towing hook centreline) to minimise the overturning moment under load
• Minimum clearance aft of the jaw for wire lead-in is typically 1.5× the maximum chain link length or wire fleet angle accommodation as specified in the approval drawing

Roller Integration

Wire entry rollers should be installed forward of the jaw at a height that delivers the wire to the jaw throat within the approved fleet angle (typically ±15°). Roller material specification matters: for HMPE lines, nylon or UHMWPE roller inserts prevent fibre abrasion; for chain, through-hardened steel rollers resist notching.

Control Panel Placement

Classification societies require hydraulic quick-release controls to be operable from a protected station with a clear view of the stern deck. For ABS and DNV notations, the panel must also be accessible from the bridge wing. Two-station control (bridge + aft deck) is standard for vessels above 80 MT bollard pull.

All wiring and hydraulic lines must be protected from mechanical damage along the full run from the HPU to the jaw body, with manual isolation valves accessible in the event of a hydraulic system failure.

Project References

Project references for tugboat shark jaw installations will be published here as documentation becomes available. Contact us directly to discuss your specific vessel requirements and we can provide relevant precedent documentation under NDA.