Editing Pipeline (section)

===Construction and operation===
Oil pipelines are made from [[steel]] or [[HDPE pipe|plastic tubes]] with inner diameter typically from {{convert|4|to|48|in}}. Most pipelines are typically buried at a depth of about {{convert|3|to|6|ft}}. To protect pipes from [[impact (mechanics)|impact]], [[abrasion (mechanical)|abrasion]], and [[corrosion]], a variety of methods are used. These can include [[wood lagging]] (wood slats), [[concrete]] coating, rockshield, [[HDPE pipe|high-density polyethylene]], imported sand padding, sacrificial cathodes and padding machines.<ref name="asme">{{cite book
| last = Mohitpour
| first = Mo
| title = Pipeline Design and Construction: A Practical Approach
| publisher = ASME Press
| year = 2003
| isbn = 978-0791802021
}}</ref>

Crude oil contains varying amounts of [[paraffin wax]] and in colder climates wax buildup may occur within a pipeline. Often these pipelines are inspected and cleaned using [[pigging]], the practice of using devices known as "pigs" to perform various maintenance operations on a pipeline. The devices are also known as "scrapers" or "Go-devils". "Smart pigs" (also known as "intelligent" or "intelligence" pigs) are used to detect anomalies in the pipe such as dents, metal loss caused by corrosion, cracking or other mechanical damage.<ref>[http://www.thefreedictionary.com/go-devil go-devil – definition of go-devil] by the Free Online Dictionary, Thesaurus and Encyclopedia.</ref> These devices are launched from pig-launcher stations and travel through the pipeline to be received at any other station down-stream, either cleaning wax deposits and material that may have accumulated inside the line or inspecting and recording the condition of the line.

For natural gas, pipelines are constructed of [[carbon steel]] and vary in size from {{convert|2|to|60|in}} in diameter, depending on the type of pipeline. The gas is pressurized by [[compressor station]]s and is odorless unless mixed with a [[thiol|mercaptan odorant]] where required by a regulating authority.