Fatigue Behaviour of Skelp End Welds in Spiral Welded Oil and Gas Pipes

石油和天然气行业对加拿大经济起着至关重要的作用。管道运营商使用埋地钢管作为运输石油、天然气和各种石油产品的主要方式。制造这些管道使用钢带，钢带变形并使用两种不同的缝焊进行焊接：直缝焊和螺旋缝焊。螺旋缝焊管与直缝焊管相比具有许多技术优势和经济效益。然而，螺旋缝焊接管的制造过程需要进给多卷钢带。两个连续带的端部在将它们送入成型机之前焊接在一起，因此，在两个连续线圈的端部连接处形成了双端焊缝（SEW）。虽然螺旋焊管现在被广泛接受为用于建筑和更换管道的直缝焊管的更便宜和更好的替代品，但包含SEW的螺旋焊管的部分被丢弃。这是因为管道运营商对使用它没有信心，因为SEW管段的疲劳性能尚不清楚。这种下料过程导致加拿大制管米尔斯的产量损失1%至5%，使其在全球市场上的竞争力下降。因此，本研究项目的目的是确定螺旋焊缝和SEW的结构完整性和安全性的一个领域的管道疲劳载荷下，主要是从工作压力的波动发展的影响。本研究的结果将提供一个洞察螺旋焊管的结构完整性，最终可以转移和使用的管道运营商和工程咨询公司。因此，加拿大的管道制造米尔斯和管道运营商，以及加拿大的经济一般，预计将受益于这一研究项目。特别是，Evraz和里贾纳的当地经济将受益于这项研究，因为Evraz在里贾纳的生产设施仅雇用500人。完成这项研究将需要对36英寸（915 mm）直缝螺旋焊接管进行大量的全尺寸疲劳试验，包括SEW和非SEW。

The oil and gas industry plays a critical role for the Canadian economy. Pipeline operators use buried steel pipelines as the primary mode for transporting oil, gas, and various petroleum products. Manufacturing these pipes uses steel strips which are deformed and welded using two different seam welds: straight seam weld and spiral seam weld. Spiral seam welded pipe offers many technical advantages and economic benefits as compared to straight seam welded pipe. However, the manufacturing process of spiral seam welded pipe requires feeding multiple coils of steel strip. The ends of two consecutive strips are welded together before feeding them into the forming machine and as result, a skelp end weld (SEW) forms where ends of two successive coils are joined. Though spiral welded pipe is now well accepted as a cheaper and better alternative to straight seam welded pipe for construction and replacement pipelines, the portion of the spiral welded pipe that contains the SEW is discarded. This is because the pipeline operators are not confident in using it as the fatigue behaviour of SEW pipe section is not known. This cropping process results in a yield loss of 1% to 5% for the Canadian pipe mills making them less competitive in the global market. Hence, this research project is aimed at determining the effect of spiral weld and SEW on the structural integrity and safety of a field pipeline under fatigue loads develop primarily from the fluctuations in the operating pressure. The results of this study will provide an insight in the structural integrity of spiral welded pipes which can ultimately be transferred and used by the pipeline operators and engineering consulting companies. Therefore, Canadian pipe manufacturing mills and pipeline operators, as well as the Canadian economy in general, are expected to benefit from this research project. In particular, Evraz and the local economy of Regina will benefit from this research, since Evraz's production facilities in Regina alone employ 500 people. Completion of this study will require a large number of full-scale fatigue tests on 36 inch (915 mm) straight and seam spiral welded pipes with and without SEW.