Deep Sea Mooring Design: Some History and New Techniques

Since 1961 ship mooring buoys have been installed in the water of the Bahamas in support of research programs at David Taylor Naval Ship R & D Center. The mooring design was first developed by DTNSRDC for water depths of 6,000 feet. The 17-ton buoy is moored to the ocean bottom with an anchor, chain, nylon line and wire rope. The service life of these moorings have been 3 to 5 years with the primary cause of failure being either corrosion and wear of the steel components (wire rope, shackles, etc.) or fish bite of the nylon line. This paper gives a brief history of these moors and it describes recent methods used to prevent failure. One method is a change out procedure for the steel components after about three years or when corrosion or wear was evident that might endanger the moor. The second method was an attempt to prevent fish bite by using a polyurethane coated line. A mooring installation is described and a new design of a termination for this polyurethane coated line is given.