Because of the high cost of replacing mooring system anchor chain, a detailed method for evaluating the remaining useful life of in- service chain was developed. The procedure was used on a first generation semisubmersible. Based on dimensional data collected from numerous independent links in a typical mooring system, chain wear patterns were developed. Magnetic particle inspection at isolated locations in each mooring line was used to ensure that surface fractures caused by eccentric loading were not present. Destructive load tests of selected chain specimens were conducted to determine the breaking strength of used chain in poor, fair and good condition. Mechanical tests and chemical analysis of the link base metal were conducted to ensure that the materials conformed to API specification. Using the data gathered, a method was developed to extend the useful life of in-service anchor chain by reorganizing individual mooring lines to take advantage of predetermined wear patterns and by downgrading the original breaking strength. A mooring forces analysis of the subject vessel was conducted to ensure that the downgraded chain strength was great enough to maintain adequate safety factors during operational and survival conditions. The procedure utilized is believed to be a conservative, practical method for determining whether or not the expense of replacing "old" chain is warranted.

  • Supplemental Notes:
    • Conference paper; Paper OTC-5719
  • Authors:
    • Dowdy, M J
    • GRAHAM, D J
  • Conference:
  • Publication Date: 0

Media Info

  • Features: References;
  • Pagination: 9p.

Subject/Index Terms

Filing Info

  • Accession Number: 00657741
  • Record Type: Publication
  • Source Agency: Maritime Technical Information Facility
  • Files: TRIS
  • Created Date: Jul 21 1994 12:00AM