Fracture-mechanics methods were used to provide a basis for assessing the significance of flaws in girth welds in a buried arctic oil pipeline. The objective was to illustrate the approach based on current knowledge and to define areas where further work will increase the validity of such analyses. The line was 1.22-m-diameter, API 5LX-65 steel with nominal wall thicknesses of 12 and 14 mm. It was field welded by a shielded metal-arc process using AWS E7010G and E8010G electrodes. Mechanical-property and simulated-service tests were made on welds cut from the pipeline. Methods were assessed for estimating weld-flaw depths and arc-burn depths from field radiographs. Various fracture-mechanics analyses were used to calculate a series of allowable flaw-size curves in accordance with worst-case requirements set by the Office of Pipeline Safety Operations (OPSO). Such curves were used to assess the significance of girth-weld flaws whose size exceeded the weld-quality requirements of API Standard 1104 and arc burns, which are prohibited by Federal Regulation 49CFR195.
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| Number of Pages : | 29 |
| Published : | 1979 |
