This paper describes the use of automatic welding and ultrasonic weld inspection for the deepwater J-Lay of the 18-inch oil and 14-inch gas export pipelines from the MARS Tension Leg Platform (TLP) in the Gulf of Mexico. While automatic welding has seen frequent use on offshore pipelines, its use on deepwater J-Lay was a first, and a significant development effort was undertaken to ensure success during offshore pipelay. To maximize the probability of detecting significant weld defects in these deepwater pipelines, especially those defects with significant through-wall height, Shell specified use of automated Ultrasonic Inspection (UT). This type of inspection can be used to quickly and accurately locate and size the through-wall dimensions of a defect. These features, in combination with the high toughness of the automatic welds, made it possible to use the Alternative (i.e. Fitness for Purpose) Acceptance Criteria of the Appendix to API 1104, instead of the workmanship criteria of Section 6 of API 1104. As such, a good balance was achieved between, on the one hand minimizing the overall repair rate by not having to repair indications that were not harmful to the weld, and, on the other hand, maximizing the probability of finding and sizing significant weld defects. This first time use of automated UT and application of fitness for purpose weld acceptance criteria on an offshore pipeline project in the Gulf of Mexico goes a long way towards validating this approach as a suitable and cost effective inspection method.


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    Title :

    Automatic welding and ultrasonic inspection for J-Lay of the MARS Tension Leg Platform export pipelines


    Contributors:
    Kopp, F. (author) / Perkins, G.G. (author) / Laing, B.S. (author) / Prentice, G. (author) / Springmann, S.P. (author) / McDermott, J.R. (author) / Stevens, D.M. (author)


    Publication date :

    1997


    Size :

    Seiten, 1 Quelle


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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