An Owner's Approach to Managing the Structural Performance of VLCCs

Abstract

An owner's experience with structural design and performance of a wide range of ship types (oil tankers, gas tankers, semi submersibles and tanker based production systems) has enabled a new approach to be devised to assessing the structural durability of a class of 5 VLCCs. These vessels were built in the mid 1970s and are experiencing varying degrees of corrosion, dependent on their operational life.The approach adopted combined conventional ship structural design techniques with structural dynamics, and fatigue and fracture mechanics techniques more commonly used in UK North Sea Offshore Projects. The combination of these technologies has led to the development of a structural management strategy for the operation of these VLCCs.The strategy has three basic components : structural enhancement, structural inspection and structural monitoring at sea. The formulation of each component is described in detail. Installation of a stress monitoring system on five ships (4 VLCCs and an Offshore Monohull Production Vessel) over the last 15 months is described and typical results presented. The importance of these results to the prediction of ship structural durability and their value in ship operation is discussed.