Safety factor requirements for the offshore industry

The maintenance of structural integrity is a significant consideration in the safety management of offshore installations. Installations operating in the North Sea are primarily of welded construction and are subjected to severe environmental conditions, which induce significant fatigue loads. Thus, offshore installations are designed to resist structural failure from fatigue and extreme loading as well as other failure mechanisms, e.g., corrosion. Additionally, design to resist failure from accidental loading, such as fire and explosion and boat impact, is recognized as being particularly important. The need to maintain safety standards is of particular relevance especially in sites where there is an increasing ageing population of installations which have exceeded their original design lives and which subsequently require reassessment to ensure that structural integrity is maintained through the life cycle. The emphasis on safety highlights the need for appropriate structural integrity assessment procedures and the use of appropriate safety factors. A particularly important development has been the major international effort since 1993 to produce an ISO standard for offshore structures. This has entailed the harmonization of relevant national codes and standards and the development of new procedures where appropriate, resulting in the derivation of revised safety factors for offshore structures. The subject of safety factors within the ISO arena and in terms of the general requirements for offshore structures is addressed in this paper.