Commercial ocean transportation of LNG first began in 1964 when ships were used to transport LNG from Arzew to Canvey Island. Almost forty (40) years has been past since then, and ocean transportation of LNG has continued to increase steadily. LNG carriers tend to be based on 20-year projects and, compared to typical commercial cargo ships, the level of equipment and materials is of a higher grade. In addition, considerable funds are being spent on maintenance and repairs, and many operators are considering ways to extend the practical operation life of the typical LNG carrier beyond 20 years. In the case of aging LNG carriers, it is beginning to become a common practice to carry out extensive refurbishing projects to extend the life of an LNG carrier and to raise the level of safety and reliability. At the present time, there are more than 50 LNG carriers of 70,000m3 or more in capacity that are over 20 years of age and are still in commercial use around the world. Life-extension refurbishing projects have already been completed for some LNG carriers. The basic specifications at the time of the original construction of the ship and the operating policies used are major factors that influence the specific content of these life-extension projects and the methods used and thus a single, unified approach cannot be used. In this paper, methods for carrying out LNG carrier useful life-extension refurbishing projects and examples of actual applications will be discussed, including the following topics: 1) LNG carrier maintenance diagnostic technology 2) Life-extension planning methods and evaluation methods related to safety and operating reliability. 3) Life-extension project execution technology.
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