Problems in underwater inspection of north sea structures

It is predicted that by 1980 there will be some 150 steel platforms and over 50 concrete platforms permanently installed in the North Sea to serve the oil industry. Nearly all of these structures will be in water deeper than 30 meters, with some at 250-300 meters. In addition some 4000 kilometers of sub-sea pipeline are projected to be in service. Underwater inspection is a requirement for these structures so that the risks of failure is minimized over their long-term operational life. This paper describes the work in progress by Det norske Veritas in underwater inspection. The "why" and "how" of under-water inspection in the North Sea are discussed and the results of recent experiences are presented. The paper places emphasis on the unique nature of underwater inspection problems with the desire to communicate these problems to other specialists. A main point made in the paper is that the state of the technology is young and that considerable potential and incentive exists for advancing this technology.