Preliminary Evaluation of the Hawaii Deep Water Power Cable for Potential of Failure Due to Erosion-Corrosion

A deep sea power cable linking the geothermal fields on the Big Island of Hawaii with the main population center in Honolulu on the island of Oahu is being designed. It will be about 250 km long and deployed at depths of up to 2200 m. These requirements demand significant extensions of current power cable technology. In this paper the potential of premature failure (in less than 30 years) due to the combined actions of erosion and corrosion is assessed. The abrasive or erosive processes become potential problems because much of the ocean bottom over the proposed cable route is covered with abrasive volcanic rocks of geologically recent origin; and because the tidal currents through the deepest channel on the route exert very significant forces on the cable. Laboratory data on abrasion of armor wire and polymeric serving materials by pillow basalt are combined with test data on corrosion of steel in deep ocean seawater to arrive at a series of worst-case estimates for the potential life reduction due to erosion-corrosion. It is shown that failure by this mechanism is a distinct possibility unless proper precautions are taken.