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The drive gear is operated with an air operated brake

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Unformatted text preview: acturing. The drive gear is operated with an air-operated brake that automatically actuates when motors are connected or disconnected. There is a safety device, which comes into operation automatically at over speed. Also the brake to regulates speed while descending by gravity. Using the gravity the cage can be brought down to the bottom of the raise in case of cutoff of air supply. The men travel in cage up to the face while the material is transported on the platform. The hoist is driven by air, and it climbs along a pin rack, which is bolted to a guiderail. The guiderail is comprised of pipes for air and water, as shown in figure2,4 13.5(c). The guiderail can be extended as the driving progresses. Each guiderail section is bolted to the rock wall (side wall) using expansion bolts. This method has following features: ● ● ● ● ● ● It makes possible to drive very long raises, vertical (fig. 13.5(c)) or inclined (fig. 13.6(ii)), straight or curved and mostly rectangular in shape. For driving blind raises of these features, even today, this method is almost a mandatory. Using guiderails the raise climber can be driven to a safe position. The guiderail curves also offers the possibility to arrange quick communication between the bottom and the work platform by a special service hoist, known as Alitrolley or Alicab, which is ready for operation on the guiderail all the time. All work is performed from the platform, which is easily adjusted for height and angle. Because of its design features for blowing air and water at the face after blasting, risks of foul gases are eliminated and the time required for ventilation get reduced. The men travel in the cage under the platform when ascending to the face or descending. All open exposure below blasted face is thus, eliminated. Connecting additional extension piece to the platform; it may be used for large areas, thereby, raises of large cross sectional areas, or the shafts can be driven. To achieve large area two parallel or opposite climbers can be used. Preparatory work and fittings A horizontal cutout (also known as raise access) as shown in figures14 13.5 (a) & (b), of 9 m (length) 4 m (width) 3 m (height) is required to accommodate raise climber with Alicab, but without Alicab its length could be 7 m. For vertical raises the © 2005 by Taylor & Francis Group, LLC EXCAVATIONS IN UPWARD DIRECTION – RAISING 337 3.3’---1 m 16.6’---5 m 10’---3 m A 45° (a) Equipment for an inclined raise Guide rails Raise access 3,3’ 3 m ---10’ 6.5’–2 m A 1m 20’---6 m Cage 6,5’ Alicab Alicab Main cage (b) Equipment for vertical raise (c) Alimak raise climber Drilling Scaling Charging Ventilation Blasting (d) Figure 13.5 Alimak raise climber – some details. curved guiderails used are: (8°, 25°, 25°, 25°, 8° i.e. the sum should be around 90°). First a vertical raise by conventional method is driven for a length of 5 m. To install the curve the brow is slashed at 45° (about 1 m from the corner), then the guiderail curv...
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