PipelinesOil pipelines are made front steel or plastic tube with inner diameter typically from 4 to 48 inches (100 to 1220 mm). Most pipelines are typically buried at a depth of about 3 to 6 ft. ( 0.91 to 1.83 m). To protect pipelines from impact, abrasion and corrosion, a variety of methods are used,The oil is keep in motion by pump stations along the pipeline and usually flow at speed of about 1 to 6 meter per second (3.3 to 19.7 ft./s). The market size for oil and gas pipeline construction experienced tremendous growth prior to the economic downturn in 2008. The industry grew from $23 billion in 2006 to $ 39 billion in2008.