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质管道作为输送石油、天然气和各种石油产品的主要方式。制造这些管子使用钢带，钢带变形并使用两种不同的缝焊方式焊接：直缝焊和螺旋缝焊。与直缝焊管相比，螺旋缝焊管具有许多技术优势和经济效益。然而，螺旋缝焊管的制造过程需要多卷钢带的补给。两个连续带材的末端在送入成型机之前被焊接在一起，因此，在两个连续线圈的末端连接的地方形成了带状端部焊接(SEW)。尽管螺旋焊管现在被广泛接受为建筑和更换管道的直缝焊管的一种更便宜、更好的替代方案，但包含缝合的螺旋焊管部分被丢弃。这是因为管道操作人员对使用它没有信心，因为缝合管段的疲劳行为尚不清楚。这一裁剪过程导致加拿大钢管厂的产量损失1%至5%，从而降低了它们在全球市场上的竞争力。因此，本研究项目的目的是确定在主要由工作压力波动引起的疲劳载荷作用下，螺旋焊接和缝合对现场管道结构完整性和安全性的影响。这项研究的结果将对螺旋焊管的结构完整性提供一个洞察，最终可以被管道运营商和工程咨询公司转移和使用。因此，加拿大管道制造厂和管道运营商，以及加拿大整体经济，预计将从这项研究项目中受益。特别是，Evraz和Regina的当地经济将从这项研究中受益，因为Evraz仅在Regina的生产设施就雇用了500人。完成这项研究将需要对36英寸(915毫米)直缝和缝制螺旋焊管进行大量的全尺寸疲劳试验。

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.