Despite low oil prices and slow world economicgrowth, pipeline construction continues at a rate of 20-25 000 kmper year. A large part of this arises through the demand for naturalgas, spurred on by the need to reduce CO_2 emissions-natural gasproduces 50 percent less than coal and 30 percent less than oil.Pipelines vary from around 15 centimetres to more than a metre indiameter and in length up to thousands of kilometres. Individualpipes are normally 12 m, or occasionally 18m in length so everykilometre of line requires 83 or 56 welded joints.
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