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FIG. 7 FIG. 8 <br />Eastern mining district bleeder system for ventilation and Continuous miner cross-entry development. <br />escapeways. <br />I UKN AIK <br />successful. But the truss system provided the best sup- <br />port and least amount of airway resistance. <br />Y <br />9 WGN~ GR~y <br /> <br />As shown in Fig. 9, thz profile of the conveyor system <br />begins at the discharge point with steep grades of 20% to <br />25% for about 2.000 m (6.500 ft). It [hen moves to a 6% <br />grade for 4.700 m (15.500 ft) in the opposite direction. <br />This bowl-shaped profile presents the engineering cha]- <br />]enge of meeting the 4.5 kt/h (5,000 stph) capacity of the <br />new longwall system and the ability to control the con- <br />veyor system. <br />One option to meet thz project criteria was to install <br />two belt systems, use a 1.52-m (60-in.) conveyor size at 5 <br />m/sec (950 fpm). A second option was to install a 1.83- <br />m (72-in.) conveyor at 4 m/sec (750 fpm). <br />The two-conveyor system would require additional <br />capital investment. It also had the control problem of <br />stopping the inby flight s}'stem without slack building up <br />or system at 5 m/sec (950 fpm) was a con- <br />ge of the inby svstem. The 1.52-m- (60-in.) <br />cern from the standpoint of provid- <br />ing the control and stopping <br />capabilitizs at the higher speed. <br />It was decided that a 1.83-m- <br />(72-in.-) wide panel conveyor was <br />the optimum s}'stem design (ur all <br />the criteria that the EMD presented. <br />The biggest concern with this system <br />was the size of the equipment and <br />the ability to handle the structure <br />and belt durine continuous miner <br />development belt moves. <br />A structure-handling machine <br />was proposed in the capital budget <br />and purchased. However, design <br />(laws have prevented the equipment <br />from being used underground. The <br />primary design problem is the sta- <br />bility of the machine, especially in <br />the steep grade areas. The 6,700 m <br />(22.(]U(1 ft) Icneth and 4.5 klt (5.(HHI <br />stph) capacity of the conveyor sys- <br />tem required a new design for fahric <br />belting at 13.8 A1Pa e'idth (2.(1(1(1 psi <br />width). <br />Two major cum-cyor belting <br />FI <br />G <br />T• <br />DECEMBER 1998 ~ MINING ENGINEERING <br />Conveyance at the dischar <br />The com~eying system design was the most challeng- wide convey <br />ing part of the long longwall panel design at Twentymile. <br />Large-diameter leg shields were able to meet the varying geologic param- <br />eters of the EMD end walkway and head clearance requirements. Shield <br />operator advances 840-t (925-stl shields. <br />