The oil and gas pipelines are connected and assembled by a single pipe one by one. Modern oil and gas gathering pipelines and oil and gas pipelines are made of steel pipes by electric welding. There are many kinds of steel pipes, such as seamless pipe, spiral seam pipe and straight seam pipe. Seamless pipe is suitable for pipes with diameter less than 529mm. Spiral seam pipe and straight seam pipe are suitable for large-diameter pipes. The cross-section structure of the gathering and transmission pipeline is complicated by the inner coating - steel pipe - outer insulation layer - thermal insulation (cold insulation) layer; the simple one is only steel pipe and outer insulation layer, while the inner coating and thermal insulation (cold insulation) layer are determined by the oil and gas transportation process.