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Anchors and chains do their hardest work out of sight. After a long stay in the Nagoya anchorage area, or after a night of heavy wind, the owner may want to know what condition they are in. An anchor chain inspection by a Diver gives a direct answer without waiting for a dry dock.
Common reasons include dragging at anchor, anchoring in strong weather, fouling of the anchor on another object, a chain that jammed or came up twisted, or a class request. Some masters also ask for a check when a ship has spent a long time at anchor and wishes to confirm that the gear is in good order before the next voyage.
At the Hull, he checks the hawse pipe, the anchor in its stowed position and the chain at the point it leaves the pipe. At the seabed or just off it, he can check the anchor flukes, the shank, the crown and the stock, and the first shackles of chain. The anchor is checked for bending, cracks, loose parts and fouling. Shackles and links are checked for wear, damage and missing studs.
Chain wear is judged by measuring the diameter of links at several points. A common acceptance rule is that the mean diameter should not be more than about 12 per cent below nominal, but the exact figure comes from the class rules or the chain maker. Large ships often carry chain with link diameters of 70 to 90 mm. Each shackle of chain is normally 27.5 m long, which helps us locate a worn length on the seabed.
Diving near an anchor needs care. The master must confirm that the windlass is secured and that the anchor will not be dropped or heaved while the Diver is below. The ship's Draft and the current can change the position of the chain, and a moving chain is dangerous. Our supervisor stops the dive the moment the ship shifts or the chain moves.
You receive the video, the photographs, the measurements and a short list of recommended actions. If a link needs replacement or a shackle is worn, the report says so and the surveyor can decide on the next step. If an anchor is lost or damaged, we can arrange recovery or repair as a separate job.
Ships that wait at the Nagoya anchorage area for several days put their anchor gear through tide changes and wind shifts. A short inspection when the anchor is raised, or a dive while the ship is still at anchor, can show if a link is worn, a shackle pin has loosened or the anchor has been bent. Owners sometimes combine this with a Hull survey, since the divers and the boat are already on site.
Class surveyors want to know the condition of the anchoring equipment during periodic surveys. Our report includes measurements, photographs and the position of each finding, so the chief officer can attach it to the ship's anchor and chain records. Any chain length with worn links is marked and photographed.
Q1. What chain wear limit is commonly used?
A common acceptance figure is a mean link diameter not more than about 12 per cent below nominal. The exact value is set by the class rules or the chain maker.
Q2. How long is one shackle of anchor chain?
A standard shackle of chain is 27.5 m, or 15 fathoms, which helps locate a damaged length.
Q3. What chain diameters are common on large ships?
Large ships often use chain with link diameters of about 70 to 90 mm.
Q4. Must the windlass be secured during the dive?
Yes. The master must secure the windlass and confirm that the anchor will not be dropped or heaved while the Diver is in the water.
