Performing ship hull inspections using a remotely operated vehicle

The Naval Surface Warfare Center, Carderock Division, NSWCCD, has been using remotely operated vehicles (ROVs) to perform underwater ship hull surveys. These deployments have been in support of research efforts in the following areas: acoustic diagnostics; magnetic signatures; cathodic protection; hull coating inspection; and hull damage assessment. 26 surveys have been performed since 1990 on aircraft carriers, cruisers, destroyers, submarines, swath hulls and piers. This paper focuses on one aspect of underwater hull inspection, the measurement of hull paint thickness. An important part of ship hull maintenance is inspecting the thickness of the underwater hull coatings. This paper describes the issues that were dealt with when such a measurement probe was deployed on US Navy ships in an industrial harbor environment. The paper also addresses the physics behind the paint thickness sensor, and its preparation for underwater use on the ROV. Results from actual deployments are reported to show that this method of data collection is valid and the probe can be used to obtain a paint thickness profile of the hull. This information was subsequently used to assist in planning the drydock maintenance package for a ship.