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<br />all asphalt \.wappiIl9 011 the outside of the pipe for corrosion protection. It <br />is assumed that steel pipe would be used since it is much cheaper than either <br />concrete or ductile iron pipe in large sizes. Ductile iron and steel pipe are <br />compal'ul,ly p.'iced in sizes up to 24", but in sizes over 24", ductile iron is. <br />more expellsive. Also, steel pipe could be fUl'nished in odd sizes, whcl'eas <br />ductile pipe would be available i~ standard sizes only. <br /> <br />Although the transmission lines are sized to deliver maximum day demunds, an <br />important consideration in the design of a pipeline is the magnitude of pressures <br />during static 0'" neal" static conditions. Pressures would be a maximum during <br />times of zero flow. Although this situation may never occur, if the pipeline <br />is designed to handle a static condition, then the system will always operate <br />under safe circumstances. As the a~ount of flow increases within a pipeline, <br />the pressure drops because of friction between the water and pipe surface. <br />So, if the maximum f10':1 in a pipeline is the amount necessary to deliver <br />max imum day demands, then pressures wi 11 be a mi n imum under those cond it ions. <br />These two f101'/ sitUution - maximum day demand and static conditions - have <br />been used to determine the possible range of pressul'es during operation of the <br />NCOHA trilnsmission lines. <br /> <br />The static pressures of the proposed NCOWA system range from 0 at the high <br />water line of the tre.1tment plant reservoir to 342 psi. at the eastermast <br />connect ion of the OiCHD. This is an e1evaton difference of from 5,420 feet <br />to 4,630 feet or 790 feet. The cost of a pipeline increases wit~.its strength, <br />so it is necessary to keep pressures down to a reasonable level. For this <br />study, 200 ps i was chosen as a max imum 1 imi 1. Pressures can be ma i nta i ned at <br />or be 10\'1 th i slim i t through the use of pressure reduc i ng val yes (PRV' s) . <br />PIlV's I.:ould he insto1l1cll at locations on the translllissioll where the static <br />pres~ure rCJLhe5 200 p,i. <br /> <br />16 <br /> <br />. . <br />