Long-distance natural gas pipelines: experience in welding and assembly?

1: For pipe weld joint alignment, internal aligners should be used primarily, with external aligners used as a supplement； 2: For relatively flat reclamation lands, economic forest areas, and hilly areas with soil (rock) texture, construction access roads are built; for each working unit, a pipe-lifting machine (assisted by an excavator) is generally used to align and weld the pipes in the ditches ； 3: In areas such as paddy fields and swamps where the groundwater level is high, it is difficult for lifting and welding equipment to move around. In such cases, it is possible to construct a pipeline prefabrication site and a launching device (using rollers) on a wider shore. Assembly and welding are carried out at the launching device; once the desired length is achieved, the winching equipment on the opposite shore is used to pull the pipeline forward. This process of assembly, welding, and pulling continues until the entire pipeline has passed through the area. After weld inspection and any necessary repairs are completed, two amphibious excavators are used to dig trenches on both sides of the pipeline, allowing it to sink naturally to the desired depth ； 4: Since it is a spiral-welded steel pipe, the spiral welds must be offset from each other by a distance that meets the specification requirements; cross welds must absolutely not occur. I think aligning long-distance pipelines is not difficult; the challenging parts are surveying and setting out, clearing the construction area, digging trenchs, transporting pipes, and laying them in place