While a vessel was in dry dock, a failing spindle caused one its anchors to fall to the bottom of the dry dock. Luckily, no personnel were in the vicinity of the dropped anchor. Root causes were discovered to be metal fatigue and a lack of proper greasing.

The incident was (anonymously) featured in Mars Report 201959 in hopes of preventing such accidents from happening. A transcript of what happened:

While in dry dock, the vessel’s anchors were ranged on the dock bottom for inspection and painting. Once the work was complete and the vessel due to depart the dock, both anchors were recovered.

The brakes were applied, guillotines dropped across the links, and devil’s claws engaged. After disengaging the clutch, the brake on the port anchor was given another turn to ensure tightness. The threaded spindle failed and the brake friction band instantly released.

At that point, the full weight of the anchor fell on the devils’ claw and dropped guillotine. The weight of the anchor forced the arms of the claw open. Although the guillotine had been dropped across the cable, it was not yet secured in place, and did not effectively stop the anchor cable running out when the claw failed. The chain and anchor ran out, unrestricted, to the dock bottom.

Investigation Findings

The investigation found, among other things, that;

  • Both linkages housing the failed threaded spindle were seized. The lack of free rotation in the linkages caused a torque to be applied to the spindle when the brake was tightened. Over time, this caused metal fatigue within the spindle until complete failure.
  • All parts of the windlass were greased regularly. However, as has been identified in other mechanical failures, grease from the greasing nipples had not penetrated every part of the equipment. This has led to the linkages becoming less than adequately lubricated.

Lessons Learned

  • When lifting or lowering anchors in dry dock, ensure personnel are clear of the area below the anchor at all times.
  • Ensure grease points are effective in delivering lubrication.

Mars Reports

This accident was covered in the Mars Reports, originally published as Mars 201959, that are part of Report Number 323. A selection of this Report has also been published in SWZ|Maritime’s October issue. The Mars Reports are also published on SWZ|Maritime’s website to help prevent maritime accidents.

More reports are needed to keep the scheme interesting and informative. All reports are read only by the Mars coordinator and are treated in the strictest confidence. To submit a report, please use the Mars report form.