Pipeline as mode of transport

Pipeline transport is the transportation of goods through a pipe. Liquids and gases are transported in pipelines and any chemically stable substance can be sent through a pipeline. Sewage, slurry, water, and even beer pipelines exist; but arguably the most valuable are those transporting crude petroleum and refined petroleum product including fuels: oil, natural gas, and biofuels. Pneumatic tubes using compressed air can be used to transport solid capsules.

Oil pipelines are made from steel or plastic tubes with inner diameter typically from 4 to 48 inches (100 to 1,220 mm). Most pipelines are typically buried at a depth of about 3 to 6 feet (0.91 to 1.83 m). To protect pipes from impact, abrasion, and corrosion, a variety of methods are used. These can include wood lagging (wood slats), concrete coating,  rock shield, high-density polyethylene, imported sand padding, and padding machines.

For natural gas, pipelines are constructed of carbon steel and vary in size from 2 to 60 inches (51 to 1,524 mm) in diameter, depending on the type of pipeline. The gas is pressurized by compressor stations and is odorless unless mixed with a odorant where required by a regulating authority.

Pipelines have been used for transportation of ethanol in Brazil, and there are several ethanol pipeline projects in Brazil and the United States. Main problems related to the shipment of ethanol by pipeline are its high oxygen content, which makes it corrosive, and absorption of water and impurities in pipelines, which is not a problem with oil and natural gas Insufficient volumes and cost-effectiveness are other considerations limiting construction of ethanol pipelines.

In places, a pipeline may have to cross water expanses, such as small seas, straights and rivers In many instances, they lie entirely on a seabed. These pipelines are referred to as marine pipelines (also: submarine or offshore). They are used primarily to carry oil or gas, but transportation of water is also important. In offshore projects, a distinction is made between a flow line and a pipeline^. The former is an interfiled pipeline, in the sense that it is used to connect subsea wellheads, manifolds and the platform within a particular development field. The latter, sometimes referred to as an export pipeline, is used to bring the resource to shore. The construction and maintenance of marine pipelines imply logistical challenges that are different from those on land, mainly because of wave and current dynamics, along with other geohazard.