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Face is scaled and after extension of the guiderail

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Unformatted text preview: reproached under the safety roof – umbrella. Face is scaled and after extension of the guiderail the cycle is repeated. The cycle of operation has been illustrated in figure 13.5(d). Performance This is the safest method to drive blind raises of longer lengths. The economy of the operation lies in compensating the cost of driving the raise access which is required to install this unit i.e. for raises of longer lengths this cost will be very nominal if raising cost/m length is calculated, but for the raises of shorter lengths this will be a substantial amount. However, its use for shorter lengths than 40 m can be made, but it would result a higher cost/m length. With regard to performance, often a two men crew can achieve installation of the climber. Initially this crew can complete a round of 1.8 to 2.4 m/shift and later on when raise length increases considerably the round in the alternate shifts. Design variants This unit is available in three basic drives operated by compressed air (e.g. STH-5L), electricity and diesel-hydraulic.2 In figure 13.7, the economical range14 and the maximum possible ranges with respect to their driving lengths have been illustrated. In figure 13.6(i) a diesel-operated unit has been shown. Figure 13.7 shows cost14 of guiderail and mounting hardware in each case for the purpose of comparison. Given below is the brief description of these units. Air driven unit The compressed air comes through the hose and the reel winds it when the climber descends. These units are normally recommended for raise upto 200 m lengths but the system has been used for the raises up to 320 m. © 2005 by Taylor & Francis Group, LLC 340 SURFACE AND UNDERGROUND EXCAVATIONS Legend Diesel/ Hydraulic ft m 1000 800 Electric Raise length 3000 2000 600 400 1000 Possible but not economical working area; special factors decide the type of raise climber. Possible working area. The increasing height, however, might involve disadvantage such as lower speed, problem with loose, cable etc. Air 200 Most economical working area 90 90 90 45° 45° 45° General recommendations for working lengths of Alimak raise climbers. Figure 13.7 Alimak raise climber – range of applicability of different models. Electrically driven unit For this unit (such as STH-5E) through a specially designed cable (weight 1–1.6 t/ 1000 m) the current is supplied to the electric motors. This unit is capable of driving raises up to 1000 m at a stretch. Longest raise driven by this unit is 950 m at 45° of 4 m2 cross-section at Denison mine in Canada. Diesel-hydraulic unit This unit can drive Raises of more than a kilometer length. This unit is self-contained (fig. 13.7) and it does not require any cable or hose. Since the air can be blown through the header, so when this unit ascends up extra air is not required to dilute the fumes of diesel motor. During its descend the motor is not run and use of gravity is made. Specially designed...
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