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ii <br />Both pipelines (6 in. ID for coarse slurry and 4 in. ID for <br />fine slurry) will emanate from the wash plant and enter the <br />return entry, as illustrated in Figure 6. <br />Underground System <br />The proposed underground system, including hydraulic pipe- <br />lines, pneumatic pipeline and dewatering/pneumatic feeding <br />station, is illustrated in Figure 7. Hoth slurry pipelines will <br />be approximately 4300 ft long with a 150 ft drop in elevation. <br />The dewatering station has been centrally located permitting the <br />pneumatic pipeline to extend to its projected 1500 ft limitation. <br />The roof height is the controlling restriction in sizing the <br />underground system equipment. Components must be chosen with low <br />profiles so as to minimize in-mine equipment transport problems. <br />Although provisions can be made for extending the roof height to <br />accommodate the dewatering equipment at the dewatering station, <br />preparation and excavation requirements for the dewatering <br />station local should be kept at a minimum. <br />The dewatering screen and solid bowl centrifuge will require <br />the highest head room. Screen drainage and centrifuge effluent <br />is normally transferred by gravity drainage to sumps/pumping <br />equipment. In this low height application, where sufficient <br />elevation for proper drainage cannot be easily attained, the <br />screen drainage and centrifuge effluent will be collected in low <br />head sumps and pumped to a controlling sump by self-regulating <br />low suction head pumps, insensitive to air ingestion. The con- <br />trolling sump will maintain a sufficient level of water to <br />prevent pump cavitation and permit adequate pumping for centri- <br />fuge effluent and screen drainage return to the wash plant. <br />Figure B conceptually illustrates the position of the de- <br />watering/pneumatic feeding equipment within a crosscut of a <br />room-and-pillar mine. <br />The roof height of the HNM crosscuts is normally 5 to 8 ft <br />and may have to be increased for installation of the dewatering <br />station. The exact height will be determined once the centrifuge <br />and dewatering screen have been sized. The major underground <br />system components include: <br />a. Solid bowl centrifuge <br />b. Double-deck dewatering screen <br />i <br /> <br />r <br />•i <br />