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Q+ <br />j0 <br />lf tlow is likety to be stopped, the designer may want <br />to provide a.means to drain the pipeline partially or <br />completely. lf, for some unforeseen reason,the <br />Driscopipe pipeline $hould plug and freeze, the <br />pipelinewill mot be damaged" The.frozen fluid may <br />bwetllhe diameter of the pipe but it will return to <br />nominal size as the fluid thaws' Due to the nature of <br />polyethylene pipe, a flame (such as a propaneor <br />hcdtytene'torch) cannot be used lo thaw a frozen <br />section of pipe, Other methods musl be used. <br />The toughrness and excellent abrasion resistance ol <br />Diiscopipe willtal<e the abuse of movement across <br />eand and soilwithout detrimental etfects on its <br />slrength or service life. l{oweven in roclqy areas, <br />sharp rocks which could cut the pipe should be <br />iemoved and may bEl replaced with a bed of sand <br />or soil. <br />' Lateral DEttectlon Due to'trhermal Mowment in Overlard <br />Pipelines. <br />The following formulae will allow the designer to <br />calculate latbratdetlection of the pipeline and anchor <br />Exanri of equation (1) ctr 2) shows that f,rr anY <br />an increase in AYwillgiven set ol conditiorl <br />AY and L to thevice versa. <br />reduce the of anchor pnirlts <br />needed b'ut .increase on the PiPe frc,rn <br />n'iovemenl may increaser possibility of kinking <br />the line if rnovefnent not occur unitormly. <br />One approach to is to calculate L <br />using (3)for strain (e)the pipe wallequalto <br />,1% and (e)to 5''lo" The at 5"/" strain will <br />give the distance anchor points and <br />should be for strain (e) and <br />minimum for L.The for L shcruld be <br />as large as other installertion <br />location duch as right-of-wa'y, slope <br />of the etc. Higher for L mean less <br />strain (e)fewenanchor and, consequently, <br />lower generally" <br />Type 3:Pipel <br />subjected <br />When piPelines <br />externat loads.l <br />buried, they are <br />effect of ext€,rnal <br />pfessufe <br />the effect <br />flexible is moro comPlex than <br />internal Pre$sure For design <br />made betweren rigid <br />increase L <br />maximum <br />purposes, <br />and <br />distinction is <br />pipes. A rigid <br />point spacing. <br />oY * LI,/3GFT <br />,AY <br />I 5q"_ <br />V.50aAT <br />, sVso"m <br />L =9F__e <br />Where: AY = Lateraldeflection (inches) <br />L = Length of PiPe between <br />anchors (inclres) <br />of the soil <br />orderto the three burrial <br />(such as c'oncrele) <br />must be spe,oified in <br />sign Parameters (wall <br />(1) <br />(2) <br />to, <br />ts to be the total andmust be <br />designod sustain all loads as well'as <br />internal But,is a flexible pipe <br />and is to be only component of the <br />more fully ort"pip+soil' <br />page 35. <br />, as clesc;ri <br />Thus, in a situation,SDR of the pipe and <br />c = Goefficient of thermalexpansion <br />(iMnfn <br />AT = Chan$e in temperature ("F) <br />e - Strain (inches/inch) <br />D = Pipe outside dia. (inches) <br />crushing,buckling anrC deflection)within <br />soilenveloperlimits, The PiPtr <br />become o/pe sYstent.'l'he interaction and <br />strength of the to tho soiland the <br />soil to the diPe resu0t in a successful integral <br />around two Points: <br />to the external <br />olhow DriscoPiPe <br />accept the backfill <br />the undisturbed walls <br />the pipeline will deflect <br />th the soil. <br />4AY2+LzH:: --_* <br />8AY