A long section of large-bore pipe used to transport fluids. Natural gas and crude oil from offshore reservoirs are transported over long distances across the seabed up to platforms for separation and treatment, and then transported sub-sea through pipelines for onshore processing. Pipelines are the principal means of transporting hydrocarbon feedstocks such as ethylene over long distances through buried pipelines between petrochemical refineries. Natural gas is transported in similar pipelines over long distances for distribution. Process water including seawater is also transported in great quantities. Pumps and compressors are used to transport such fluids in large volumes at the required pressure. Single-phase flow is easier to transport and meter than multiphase fluid flow. In wet gas lines, large volumes of liquid are required to be routinely swept out using a pig. Methane clathrate, waxes, and other deposits can also complicate flow.