201408 Lost anchor a mystery

The starboard anchor was weighed and the vessel proceeded to berth. The starboard anchor was again used during berthing along with the mooring lines as per the port procedures, and six shackles were deployed in 25 metres of water. The next day, after discharging a parcel of cargo, the vessel was departing the port; the anchor was to be weighed after letting go the lines. As the starboard anchor broke the surface of the water the officer on duty informed the wheelhouse that the flukes and crown of the anchor were missing.

Root cause
This could be due to a latent defect, as such an occurrence is unusual under normal usage. Even under excessive load conditions, the D Shackle on the chain, which is the weaker link, should break first. This indicates a probable casting defect which has surfaced after three years of use.

Editor’s note: Although it is difficult to appreciate a lesson learned here, casting defects do occur from time to time. It is prudent practice when in drydock to carefully examine all ground tackle for defects. But even a thorough visual examination can miss a casting defect which is hidden within the gear. Some inspectors use a hammer test that may reveal casting problems or other defects.

 

 

Reader's response published in July 2014 issue of Seaways

In the reported case, close examination of the surface of the material where the anchor shank failed could perhaps determine the cause of the failure. Depending on the importance of the matter, the shank could be lab tested to find out the exact cause. The Master/owners could refer to the certificate of the anchor and take up the matter with the suppliers of the anchor. Obviously the classification society would also like to establish the cause of the failure and take corrective action.