Gas distribution networks
Introduction
A gas pipeline, also called gas pipeline, is an infrastructure composed of a network of large pipes that allows the transport of fuel gases on a large scale over long distances.[1][2][3].
Construction
It consists of a pipeline through which fuel gases, mainly natural gas, circulate at high pressure from a point of origin to a distribution center. They are built buried in trenches at a usual depth of one meter and up to two meters, depending on the terrain and safety. Exceptionally, they are built on the surface.
For safety reasons, the regulations of all countries establish that valves be placed in gas pipelines at certain intervals, through which the gas flow can be cut off in the event of an incident (such as a lack of pressure due to a gas leak). In addition, if the gas pipeline is very long, it may be necessary to place compression stations at intervals, as well as fiber optic cables (for the transmission of information and the detection of gas leaks in the pipeline), emergency stations, fire fighting equipment and roads to access the location of the gas leak.
The beginning of a gas pipeline can be a field or a regasification plant, generally located near a seaport where ships arrive (for natural gas, they are called methane carriers), which transport liquefied natural gas in cryogenic conditions of very low temperature (-161 °C). They are also built to connect gas plants with bottling plants in cities, for filling gas cylinders, or for distributing gas through pipes to cities, consumer centers, industries and electrical generating plants.
To cross a river in the layout of a gas pipeline, two techniques are mainly used: horizontal drilling and directional drilling. With them it is achieved that both the flora and fauna of the river and the "Ribera (bank)" bank are not affected. These techniques are also used to cross other important infrastructure such as roads, highways or railway lines.
Laying by sea is done from specially designed ships, which deposit the pipe on the seabed once it has been welded on the ship, with a special pipe installation system as in the North Sea, England, Norway and Russia, with large ships that function as pipe factories and deposit the pipe on the seabed.
Particular regulations in many countries require that buried gas pipelines be protected from corrosion. Often the most economical method is to line the conduit with some type of polymer, so that the pipe is electrically isolated from the surrounding ground. It is generally coated with paint and polyethylene up to a thickness of 2-3 mm. To prevent the effect of possible failures in this coating, gas pipelines are usually equipped with a cathodic protection system, using sacrificial anodes that establish sufficient galvanic tension so that corrosion does not occur in the tube, anodes that must be changed during their operation over the years.