NDLI: Fatigue Strength of Heavy Wall Line Pipe Girth Weld for J-Lay Installation

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Marines-Garcia, Israel Pelcastre, Mauricio Garcia, Enrique Philippe, P. Darcis Yang, Guangqiang Bourgeois, Desmond Visco, Tyler
Copyright Year	2018
Abstract	Tenaris and ExxonMobil conducted a qualification program focused on Heavy Wall Seamless Line Pipe (HW SMLS LP) and its girth welds, to experimentally demonstrate and validate the material potential to be used as riser or fatigue sensitive flowline for the development of challenging deep and ultra-deep offshore fields. The qualification program was divided in three phases. Phase I [1] included: 1) HW SMLS LP, X65QS, 273 mm OD, 46 mm WT plain pipe qualification; and 2) development and qualification of a WPS (STT® process for root pass and GMAW process for hot, fill & cap passes, narrow groove J-bevel type, 1G welding torch position) and full scale fatigue testing qualification. Phase II [2] was focused on evaluating the root girth weld fatigue endurance, taking into account the fatigue behavior observed in Phase I (fatigue crack initiation mainly occurred from the outer surface). The fatigue strength of the weld root surface is needed as the weld root surface is in direct contact with corrosive fluids and is the most sensitive area for sour service applications. Thus, to obtain the root girth weld fatigue endurance, full scale fatigue specimens were manufactured with their caps fully removed (by grinding and flapping) to generate weld cap toe free of stress raisers/imperfections. In addition, pipe outer surface was grinded to mitigate the fatigue crack nucleation from outer pipe surface. With this special preparation, the fatigue strength of weld root surface was able to be assessed. This paper presents Phase III qualification outcomes. The objective was to develop and qualify a WPS representative of J-Lay installation, meaning 2G welding torch position (CMT® for the root pass and pGMAW process for hot, fill and cap passes, Narrow groove J3°-bevel type). The qualification included full scale fatigue assessment as well. The LP material was from the same batch used in Phase I & II (HW SMLS, X65QS, 273 mm OD, 46 mm WT). The WPS was successfully developed and qualified. The full scale resonant fatigue testing included three specimens with cap smoothed similarly to Phase I, and three specimens with full cap removal plus outer pipe surface grinding similar to Phase II. The fatigue results surpassed the expectations (Class D, S-N curve). Most of the specimen’s fatigue lifetime is above the class B, S-N curve classification (reference for plain material). Obtaining a smooth root weld overfill was key to delaying the fatigue crack nucleation from the weld root toe.
Sponsorship	Ocean, Offshore and Arctic Engineering Division
File Format	PDF
ISBN	9780791851234
DOI	10.1115/OMAE2018-78056
Volume Number	Volume 4: Materials Technology
Conference Proceedings	ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering
Language	English
Publisher Date	2018-06-17
Publisher Place	Madrid, Spain
Access Restriction	Subscribed
Subject Keyword	Gas metal arc welding Fatigue testing Welding Fatigue Grinding Stress Nucleation (physics) Pipeline risers Welded joints Fluids Fatigue strength Ocean engineering Resonance Performance Risers (casting) Pipes Fatigue cracks
Content Type	Text
Resource Type	Article

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