9781439834220.ch13

The manufacturer can supply platforms of 16 m 16 m or

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Unformatted text preview: e is fixed by lifting it with the help of pulley – block. The manufacturer can supply platforms of 1.6 m 1.6 m or 2.4 m 2.4 m or any other size. Unit has safety devices for over-speed control, and to guard against the air supply failure. It has got a steel umbrella and fencing attached with platform for the safety purposes. © 2005 by Taylor & Francis Group, LLC 338 SURFACE AND UNDERGROUND EXCAVATIONS Air Electric Diesel (i) Alimak raise climbers motive power: Air, electric and diesel (ii) Alimak raise climbers for: Vertical, inclined, and wider raises with extension platform 20 18 16 (iii) Drilling pattern: Cylindrical cut for Alimak raise faces of 2 m 2 m 16 14 4 18 16 10 12 9 20 18 12 16 6 2 01 3 7 5 14 8 18 Figure 13.6 Alimak raise climber – Classification, applications and drilling pattern for 4 m2 raise. 13.8.1.2 Ignition and telephone systems To eliminate the need of a separate cable for the blasting operation, a steel wire having strong insulation, is pulled through one of the guiderail pipes. When firing a round, the current goes through the closed circuit formed by the wire and through the guiderail itself. The same cable system is used for providing alarm and telephone communication between the platform and the base. While drilling the face a header is fitted to the top most guiderail but on completion of the drilling operation this is replaced by the header-plate having nozzles fitted to it; so that it can be utilized to blow air and water effectively after blasting operation at the face to clear the fumes, dust and ventilate the face effectively. It is also possible to adjust water and air supply through the © 2005 by Taylor & Francis Group, LLC EXCAVATIONS IN UPWARD DIRECTION – RAISING 339 central, however, for the raises of longer lengths installation of a booster pump for achieving required water pressure at the time of drilling, may be necessary. There are four pipes in the guiderail, two for compressed air, one for water and the fourth one meant for the remote control operation of the air and water valves. The central is fixed in the Alimak raise access, to this incoming and outgoing connection for air and water is made. Air supply to the hose reel is also given from this. While extending a guiderail, a guiderail of required length, bracket, expansion bolts, O-ring, U-washers, bolts and nuts, spacers and header plate with cocks, are required. 13.8.1.3 Cycle of operations Drilling is done from the working platform. A safety belt must be used if the gap (distance between side walls and the platform) exceeds 15 cm. The drilling patterns usually drilled are: burn cut or pyramid cut, based upon the situation and the type of the rock. In case of burn cut, the cut holes, should be positioned either at the center or opposite side of the guiderail to protect them from the direct rock hit. On completion of drilling the face is charged with explosives and the header is replace by a header-plate. Before blasting the cage is brought to the raise inset. After blasting, the air and water jets from the header plate clear the fumes and then face is...
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