By MarEx 2015-05-12 19:43:14
The U.S. Coast Guard has issued a safety alert after an incident where an anchor slipped and punctured a ship’s hull.
The cargo ship was underway in 15 foot seas when the forepeak flood alarms activated. The crew investigated and discovered the starboard anchor had slipped 10-15 links, causing it to strike and puncture the hull. As a result, seawater flooded the bow thruster and emergency fire pump compartment.
The casualty resulted in excess of $1 million in vessel damage and a month’s lost revenues while the vessel was out of service affecting repairs. During the repair period, it was discovered that the anchor windlass brake pad had worn down to 2-3mm thickness. With only this amount of pad the fully applied brake could not achieve its designed holding power. The crew should have recognized the excessive wear to the brake pads and required replacement, says the safety alert.
It was also discovered that the involved anchor had dissimilar specifications to the original anchor it had replaced. As a result, the replacement anchor’s relative position in the hawse pipe was not the same because of its different shank length and connecting linkages. The size difference prevented the riding pawl from properly engaging the anchor chain.
As an added safety device, a wire sling had been used to secure the anchor. The wire sling was threaded through a chain link and secured to the vessel with a pelican hook. When the sling broke and the brake failed, the anchor’s weight and ship’s movement then caused it to drop before the riding pawl could properly engaged. The sling failure was likely caused by the corrosion of the inner wire strands. The inner wire strands were exposed to the elements because of the sharp bend in the wire created by being fed through the chain link and secured by a pelican hook.
The wire sling was inspected regularly. However, those performing the inspections were not instructed on how to examine and determine its serviceability.
The safety alert reminds vessel operators and company technical managers of the importance of proper ship’s anchor use, stowage and maintenance. Anchor windlass brakes, riding pawls, and devil’s claws must be used as designed and periodically maintained to ensure effectiveness and safety.
It’s critical that proper supervision and inspection be conducted during and after anchoring, retrieving and storage evolutions, and maintenance activities. When installing a replacement anchor, it must meet the vessel’s technical specifications and fit correctly when housed.
The full safety alert is available here.