Vessel Anchoring Systems: Loss Prevention and Maintenance

Introduction

The anchoring system is a critical component of a vessels safety equipment, essential for emergency maneuvering, station keeping, and disaster prevention. The loss of an anchor or failure of the anchoring system can lead to groundings, collisions, or drifting into hazardous waters. This guide outlines industry-standard practices for the maintenance and operational safety of anchoring gear.

Common Causes of Anchor Loss

Understanding why anchors are lost is the first step in prevention. Most incidents stem from a combination of environmental factors and mechanical wear:

• Chain Wear: Extended service life leads to thinning of chain links, particularly in the "wet locker" section where salt water accelerates corrosion.
• Shackle Failure: The failure of common links or joining shackles due to fatigue, improper installation of locking pins, or corrosion.
• Windlass Overload: Attempting to break an anchor out of heavy, sticky, or rocky seabed conditions beyond the windlasss safe working load.
• Improper Seating: Failure to secure the anchor firmly in the hawse pipe or bolster, leading to vibration damage during transit.
• Swivel Failure: The swivel is often the weakest point in the connection. If the swivel becomes jammed or suffers from galvanic corrosion, it can snap under tension.

Preventive Maintenance Guidelines

A rigorous inspection and maintenance schedule is vital to ensure the reliability of the system.

Regular Inspections

Inspections should be conducted at predefined intervals and documented in the vessels Planned Maintenance System (PMS):

• Monthly Inspections: Inspect the windlass motor, brakes, and hydraulic systems. Check for signs of grease leakage or unusual noise.
• Quarterly Inspections: Examine all exposed chain links for signs of excessive wear (exceeding 12% of the original diameter), cracks, or deformation.
• Dry-Docking/Anchor Walk: When the vessel is in dry dock, the entire cable length should be laid out. This allows for an ultrasound thickness measurement of the chain links. Chains should be rotated periodically if wear is uneven.

Lubrication and Corrosion Control

Corrosion is the primary enemy of the anchoring system. Applying a suitable protective coating or marine-grade grease to the shackles, swivels, and windlass components is necessary. Ensure that the chain locker is well-drained to prevent the buildup of mud and stagnant water, which accelerate the deterioration of the chain.

Operational Best Practices

Even with perfect equipment, improper handling can lead to system failure. Adhere to these operational guidelines:

• Control the Descent: Never allow the anchor to "free fall" to the seabed unless strictly necessary. Always use the windlass to lower the anchor to a certain depth to prevent damage to the windlass brake and the chain.
• Monitor Tension: During heavy weather, the windlass brake should be backed up by a chain stopper (guillotine bar). The windlass itself should not be left to bear the full load of the vessel during sustained high winds or current.
• Clear the Seabed: If the anchor does not break out easily, do not use the windlass to force it. Utilize the vessels engines to maneuver over the anchor and minimize the vertical strain on the equipment.
• Securing for Sea: Once the anchor is stowed, it must be properly secured. The guillotine bar must be engaged, and the lashings must be tensioned to prevent any movement while at sea.

Record Keeping and Documentation

Maintain accurate records of the chain length, the number of shackles, and the results of all inspections. Any part replacedsuch as a joining shacklemust be logged with its certificate of quality. If a chain link is found to be below the allowable diameter, it must be marked for replacement or the entire length of the cable must be derated in the ship's stability and safety manuals.

Conclusion

Anchor loss is frequently preventable through consistent maintenance and vigilant operation. By ensuring that all componentsfrom the anchor shackle to the windlass brakeare regularly inspected, lubricated, and operated within their design limits, crew members can significantly reduce the risk of critical equipment failure, thereby enhancing the overall safety of the vessel and its crew.