PIPE DRIFTING

See here! http://www.glossary.oilfield.slb.com/Display.cfm?Term=drift

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This is exactly what i am looking for. Thank you charsley99

Think of drifting like the rails of a railway when a heavey train goes over it espically around curves at high speed. The rails move for many many miles along the track with the ties holding them the movement is lessened but still noticable. Stand along a track sometime when a heavey loaded train comes around a curve and watch the track almost fighting to breakfree and twist. Ot really is a sight and helps kids to understand the use of materials and their strenghts to control the effects of pressure of a different force.

Pipeline move because of the weight of whats being pumped thru, the pressure at which it is pumped, the gravity froces that pull on the product espically in curves or at joints and any ground movement which is constantly going on.