This paper describes the life extension of a semi-submersible drilling rig built in the early 1970's. A programme of work was devised which included the following steps: 1) finite element modelling of the rig, and estimation of fatigue life based on S-N techniques; 2) inspection of the structure in dry dock; 3) application of fatigue life improvement techniques (weld toe grinding) in critical areas of the fig; 4) sampling and testing of parent material and weldments, taken directly from the rig; and 5) fracture and fatigue crack growth analysis using fracture mechanics techniques. The life extension strategy made use of a number of aspects of offshore technology which were not available at the time of construction of the rig. The programme demonstrated the feasibility of extending the operation of the rig for a further 20 years, with the interval between in-service inspection increased to every five years. It also provided a valuable database of fracture toughness data for the rig materials, which may be used in future work to address reliability issues.

  • Supplemental Notes:
    • OMAE 1995, 14th Intl Conf on Offshore Mechanics & Arctic Engng; 18-22 June 1995; Copenhagen, Denmark. Sponsored by ASME et al. Procs. Publ by ASME, ISBN 0-7918-1307-X. Vol I, Pt B, p 143 [10 p, 11 ref, 1 tab, 10 fig]
  • Authors:
    • Hadley, I
    • Sinclair, C I
    • Magne, E
  • Publication Date: 1995


  • English

Subject/Index Terms

Filing Info

  • Accession Number: 00718532
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Mar 27 1996 12:00AM