الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
every engineering structure and component the possibility of including a defect into it that will later increase in size and impair the efficiency, or produce total failure of the structure or the component is a real danger.With an offshore structure, its life can be divided into four distinct stages. These are listed below together with possible defects that may occur at that stage. i) Manufacture of material, e.g. steel; Cracks, segregations, shrinkage impurities, porosity.ii) Fabrication; Machining defects, residual stress, heat treatment defects, welding defects, fitting stresses, sharp edges. iii) Installation; Micro cracking due to high loading, residual stresses due to deformation of material, damage due to bad handling. iv) In-service; Deterioration due to fatigue, corrosion, erosion, wear, stress corrosion, corrosion fatigue, embrittlement, accidental damage. Ideally, the structure or component will be inspected at each stage so that when the structure comes into service a complete profile history of defects is available. However, defects at any stage may pass undetected, so underwater inspection at stage four must be capable of detecting all the above possible defects. To this end, advanced inspection techniques such as magnetic particle inspection and scan ultrasonic have been developed for underwater use. Upon results of these tests, underwater repair and maintenance would be carried out such as underwater cutting / welding, cracks repair, hull blanking, rudders and propellers repair, anodes installation or replacement.