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n want Examinatim of equation(1)or(2)shows that for any r If flow is likely to be stopped,the designer may iven set of thermal conditions an increase in AY will to provide a.means to drain the pipeline partially or g n reason,the increase L and vice versa. Increasing AY and L to the completely if,for some unforesee Driscopipe pipeline should plug and freeze,the maximum will reduce the number of anchor points pipeline will not be damaged.The frozen fluid may needed but may increase wear on the pipe from t it will return to movement and may increase the possibility of kinking swell the diameter of the pipe bu e nature of the line if lateral movement does not occur uniformly. nominal size as the fluid thaws.Due to th polyethylene pipe,a flame(such as a propane or One practical approach to design is to calculate L acetylene torch)cannot be used to thaw a frozen using formula(3)for strain(s)in the pipe wall equal to section of t Other methods must be used. 1%and(e)equal to 5%.The L value at 5%strain will pipe. The toughness and excellent abrasion resistance of give the shortest distance between anchor points and should be considered maximum for strain(s)and 'Diiscopipe will take the abuse of movement across minimum spacing for L.The spacing for L should be sand and soil without detrimental effects on its as large as possible considering other installation strength or service life.However,in rocky areas, location factors,such as available right-of-way,slope sharp rocks which could cut the pipe should be of the ground,etc.Higher values for L mean less removed and may be replaced with a bed of sand strain(s)and fewer anchor points and.consequently. or soil. lower costs,generally. Lateral Deflec*m Due toThermal Movement in Overland Type 3,Buried Pipelines Pipelines. tntroduc6on When pipelines are buried,they are L —L f subjected to external loads.The effect of external pressure on flexible Driscopipe is more complex than t—AY the effect of internal pressure only.For design �Y \—pipe And" purposes.a distinction is usually made between rigid and flexible pipes.A rigid pipeline(such as concrete) The following formulae will allow the designer to is considered to be the total structure and must be calculate lateral deflection of the pipel'uie and anchor designed to sustain all external loads as well as point spacing. internal pressure.But.Driscopipe is a flexible pipe = and is considered to be only one component of the DY i-�T (1) "pipe-so}7"system,as described more fully on AY page 35: L = (2) Thus,in a buried situation.the SDR of the pipe and a (3) the-strength of the soil envelope must be specified an D 96aAT order to keep the three burial design parameters(wall L = kling and ring deflection)within e crushing.wall buc acceptable limits.The pipe and soil envelope Where: AY =Lateral deflection(inches) become one system.The mutual interaction and L =Length of PiPe between strength contribution►of the pipe to the soil and the anchors(inches) soil to the pipe result in a highly successful integral . a =Coefficient of thermal expansion rots: (i�� structure.Correct design centers around two po a)matching the proper wall-thickness to the external AT =Change in temperature("� soil pressure and b)the analysis of how Driscopipe s =Strain(inches!►nch) and ending the pipe accept the backfill D =Pipe outside dia.(inches) earthloading and transfer it to the undisturbed wails ®Y of the ditch or trench such that the pipeline will deflect • slightly into static equilibrium with the soil. Lf R=Radus R_4AY2+12 8AY 34