Transportation pipelines are built for the purpose of transporting a liquid or gaseous commodity from points of production to process facilities, or from points of refinement to storage or end-use customers. They exist as alternatives to other modes of transport, e.g. railroad, trucks, barge, or ship and thus are regarded as transportation systems. Transportation pipelines include gathering lines from production wells to processing or refinement facilities, transmission lines from processors to storage or from storage to distribution systems or industrial customers, and distribution systems, e.g., truck terminals for refined fuels, or mains and services for natural gas. Gathering and transmission pipelines may also exist offshore.

Transportation facilities include underground storage and above ground tankage, pumping, compression, metering, and distribution or terminals. The processing of transported commodities, which may include removal of contaminants, separation of condensates, blending, or other refinement steps, is outside the scope of transportation. Filtration, liquid separation, dehydration, odorization, metering, pressure regulation, pumping and compression can occur in conjunction with handling the main product stream and thus are typically within the scope of transportation.

Pipelines comprise a ubiquitous, yet largely hidden, infrastructure. In the United States, there exist approximately 300,000 miles of gas transmission pipelines [1], 190,000 miles of hazardous liquid pipelines [2], and 2.1 million miles of gas distribution mains and service lines [3]. Commodities transported by pipeline include: crude oil, motor fuels and other refined petroleum products, liquid fertilizers, carbon dioxide, chemical feedstock, and natural gas. Pipelines performing similar functions to those described above are in use worldwide, so ASME pipeline standards have worldwide utility.