Welding the first ERW X80 grade pipeline
Pipeline materials and construction costs are significant components of major transmission pipelines. In Australia, these costs have been contained over the past two decades by the utilisation of high strength thin walled pipe.
API 5L X70 grade pipe is common place in Australian pipelines, however, a trial section of 13km of 8.8mm thick 406mm diameter API 5L X80 grade pipe has been installed in a looping section of the Roma-Brisbane pipeline.
The aim of this trial section was to evaluate the economic benefits associated with the use of X80 grade pipe. The evaluation involved development of weld procedures using both the conventional cellulosic manual metal arc (MMA) process and a mechanised gas metal arc welding (GMAW) system to determine the influence of weld metal strength on allowable girth weld defect tolerance.
Using currently available cellulosic consumables full section pipe tension tests demonstrated tolerance to both Tier 1 and Tier 2 girth weld defect allowances. These results support recent research that has shown that the tolerable level of weld metal strength undermatching is related to the pipe wall thickness and the defect depth assumption.
Weld metal strength matching with an appropriate level of toughness was shown using engineering critical assessment procedures to provide increased defect tolerance. Destructive test methods, developed at BlueScope Steel in conjunction with the Pipeline Industry, provide a more accurate assessment of girth weld defect tolerance.
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Click here to read the full paper by Barbaro F J, Bowie G F and Holmes W: Welding the first ERW X80 grade pipeline (585 KB)
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This paper was first published in the proceedings of the Welding Technology Institute of Australia International Conference on 'Pipeline Construction Technology', 4-5 March 2002, Novotel North Beach, Wollongong, Australia.
