Some new approaches to the construction of foreign gas pipelines

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Some new approaches to the construction of foreign gas pipelines – I came across them in a magazine and thought they were valuable, so I’m sharing them here; please point out any mistakes if there are any. In recent years, abroad, particularly in North America, some new approaches have been adopted in the design and construction of gas pipelines, which are highly instructive; a summary is provided below. It was found that in previous valve rooms, gases, water, and moisture tended to accumulate, and insects as well as wild animals could easily get in, which posed risks and negative impacts on the safe operation of the pipelines. Therefore, in North America, the mainline valve chambers have been eliminated; the mainline valves are buried directly underground without any additional facilities. At the same time, this can also eliminate the need for gas detection equipment, saving on investment costs. Increase the maximum allowable operating pressure of the branch pipelines. In the past, the design pressure of branch pipelines was always lower than that of the main pipelines; therefore, pressure-reducing devices were installed at the junctions between branch and main pipelines. In recent years, in North America, some branch pipelines have been designed and pressure-tested at the same pressure as the main pipelines. This not only eliminates the costly pressure reduction devices at the branch pipe connections, but more importantly, it increases the amount of gas that can be stored in the branch pipes, thereby meeting the requirements for hourly load balancing as well as the needs of future additional users. Increasing the design pressure of the branch pipelines necessarily requires raising the ANSI pressure ratings and pipeline classes of the flanges and valves, resulting in additional investment. However, as demonstrated by multiple piping systems, the additional investment is negligible compared to the economic benefits resulting from increasing the design pressure. The valves are connected to the main pipelines by welding rather than using flanges, as flange connections are prone to leaks; in the event of a leak, the entire pipeline must be shut down in order to carry out repairs. Welded joints can avoid such problems. l Pipes with a continuous concrete coating are used: In most sections where pipelines cross small rivers and wetland ditches, pipes with a continuous concrete coating are employed, rather than saddle-shaped or bolted concrete weight blocks. The use of pipes with a continuous concrete coating not only helps to stabilize the pipes and prevent them from floating, but the concrete coating also protects the pipes’ anti-corrosion coating during installation, reduces the requirements regarding the quality of the backfill soil, and improves economic efficiency. Continuous concrete coatings can be mixed and applied on-site. On-site patching techniques: In North America, due to the difficulties involved in the construction process, no pipeline company uses shrink sleeves for repairing large-diameter pipes; instead, they employ coatings such as liquid epoxy coatings, polyurethane coatings, and FBE coatings. In North American engineering practices, the support for underground pipes is placed beneath the pipes themselves, rather than beneath the valves. The pipe supports are adjustable, allowing for adjustment in case the foundation settles. Regarding the standardization and unification of measuring equipment, only one standard type of ultrasonic flow meter is used in the newly built ALLIANCE pipeline; this simplifies the operation of the pipeline system and reduces the costs associated with the operation and maintenance of measuring equipment. Other practices include: not installing cyclone separators at the export metering stations, and not providing vent pipes at the pigging stations and metering stations.