9781439834220.ch4

18 kg light 1825 kg medium 2530 kg heavy over 30 kg

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Unformatted text preview: ral utility Shaft sinking Drill Class J/H or Sinker V light . 18 kg Light 18–25 kg Medium 25–30 kg Heavy over 30 kg 50–70 70–100 100–120 120–140 2 2–2.5 2.5–3 Over 3 19–32 32–38 35–41 38–44 0.3–0.6 0.6–1.2 1.2–2.4 1.2–3.7 Jack drill Medium 60–66 mm or Heavy 68–83 mm jackleg 150–160 180–210 3–4 4–5 32–41 38–44 1.2–3.7 Drifting, stoping, 1.2–3.7 Drifting, stoping Stoper Light 34 kg Medium 34–45 kg Heavy over 45 kg 150–170 170–190 190–210 3–3.5 3.5–4 4–5 32–38 35–41 38–44 1.2–3.7 Raising 1.2–3.7 Raising, stoping 1.2–3.7 Raising, stoping Drifter Light 83–102 mm 200–300* 6 Medium 102–114 mm 300–400* 6–10 Heavy Over 114 mm 400–500* 10 38–44 41–51 44–57 1.2–2.4 Small tunnels 2.4–3.7 Medium tunnels 3.7–30.5 Large tunnels and longholing # – Air consumption for riffle-bar drills with water flushing. The water pressure should be equal to or slightly less than air pressure. The air pressure for all these drills is 620–690 kPa (90–100 psi). * – add 0.071 cum./sec (150 cft) for independent rotation. The rock drill jackleg is made by clamping a pusher leg to jack hammer to support the weight of the machine and to feed the tool forward in horizontal or upward direction (fig. 4.5(c)). These are generally classified as per cylinder’s bore size as medium or heavy duty. The bore size ranges from 60 to 83 mm. Due to their lightweight and versatility these are very effective in small sized drifting, tunneling or heading, and stoping operations. Hand held and pusher leg mounted drills, even today, remains a widely accepted choice in most of the drivage work. But so far rate of drilling and precision is concerned this technique has got limitations as in this case the feed thrust has to be balanced by the man’s weight and strength. Pusher leg drilling is an arduous as well as a © 2005 by Taylor & Francis Group, LLC 68 SURFACE AND UNDERGROUND EXCAVATIONS skilled task, and rock drill performance has to be matched with physique and skill of the operator. The stoper is a jackhammer, which is rigidly attached to a pneumatic cylinder for drilling holes in the upward direction. The cylinder or leg may be in line with the drill, or it may be offset from the drill line, to provide a short overall length for drilling in low height workings. The stoper is often designed with a jackdrill as its base, and therefore, it is available in the same bore size range as the jackdrills. Its weight ranges from 34 kg to more than 45 kg. It is used for raising and stoping operations for drilling either vertical or steeply inclined up holes. In case of conventional drills apart from the limitations listed above, in a specific situation where rapid drilling cycles are required, particularly in small headings the problem of over crowding these machines arises, and practically a limit comes when both the men and the machines unable to function effectively. Looking into these problems further mechanization in drilling operations has been brought about by the introduction of drilling jumbos as shown in figure 4.5. These jumbos usually consist of high performance rock drills called drifters (fig. 4.5), mounted on a feed system, which is supported by a boom. The feed alignment to ensure drilling of parallel holes is based upon a moving parallelogram mechanism with the links either mechanically or hydraulically operated or positioned. All the controls are lever or valve operated. In order to ensure several drills to be operated by one operator, mechanisms are available to stop the drill when the hole is completed and to return to its original position, completely automatic. All that an operator has to do is to reposition the boom for its next hole and start drilling. Stan...
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