Hot tap connections of pipelines

管道热抽头连接可以在不关闭运行管道的情况下将新管道连接到正在运行的管道上。由于管道可能花费数亿美元或更多，因此给客户带来不便并避免因关闭而导致的收入损失对TCPL来说是有价值的。虽然目前已经存在将小直径管道连接到大直径管道的技术，但拟议的研究将开发最先进的计算机模型来优化该技术，评估其现有方法的稳健性，并将该技术扩展到连接几乎相同直径的管道。焊接是一个非常复杂的过程，涉及到从熔化到凝固的完整材料处理，并在大约1秒的时间内形成大约1cm ^3的成品焊接池。由此产生的微观组织控制着焊缝性能。控制热量从管道外壁上的焊缝流向管道内壁的对流系数和环境温度取决于管道内流体的流速、压力、温度和类型。这控制了低合金管线钢的冷却速度和焊缝熔合及焊缝热影响区的显微组织。这对于具有较高碳含量和铁素体-珠光体微观结构的旧管钢尤其重要。目前的技术采用冷却速率测试，将管道外壁上直径约50毫米的圆形块加热到300摄氏度左右，并测量将加热区域冷却到高于环境温度100摄氏度和15摄氏度所需的时间。根据这些测量的冷却时间，基于实验的规则被用来判断热水龙头是否可能成功。在本研究中，计算机模型将根据冷却速率试验数据计算对流系数，并预测热熔接焊缝的显微组织、硬度、残余应力和变形。我们建议将TCPL档案中有关热攻焊缝的数据进行关联，以验证计算机模型。

Hot tap connections of pipelines enable a new pipeline to be connected to an operating pipeline without shutting down the operating pipeline. Since a pipeline can cost hundreds of millions of dollars or more, inconveniencing customers and avoiding the lost income that would be incurred by a shut down is valuable to TCPL. Although the technology to do this for connecting smaller diameter pipes to larger diameter pipes exists, the proposed research will develop state of the art computer models to optimize this technology, to assess the robustness of their existing methodology and extend this technology to connect pipes of nearly equal diameter. Welding is a very complex process that involves complete material processing from melting to solidification and shaping the finished weld pool of roughly 1 cm^3 in times of roughly 1 second. The resulting microstructure controls the weld properties. The convection coefficient and ambient temperature that controls the flow of heat from the weld on the external wall of the pipe to the internal wall of the pipe is dependent on the flow rate, pressure and temperature and type of fluid within the pipe. This controls the cooling rate and microstructure of the weld fusion and weld heat-affected zone in low-alloy pipeline steels. This is particularly important in older pipe steels that have higher carbon levels and ferrite-pearlite microstructure.Current technology uses a cooling rate test that heats a circular patch about 50 mm diameter on the outer wall of the pipe to about 300 degrees C and measures the time it takes to cool the heated area to 100 degrees C and to 15 degrees C above ambient temperature. From these measured cooling times, rules based on experiments are used to judge if the hot tap is likely to succeed. In the proposed research, a computer model will compute the convection coefficient from the cooling rate test data and predict microstructure, hardness, residual stress and distortion in the hot tap weld. We propose to correlate data in TCPL's archives on hot tap welds to validate the computer model.