Background Papers for a Drilling Technology Workshop (1975) / Chapter Skim
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Pages 106-126
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From page 106... ...
systems changes as materials and designs improve. In this country, however, the rotary-percussive system has been largely neqlected so that the choice becomes much more simple.
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From page 108... ...
systems could then be compared and the optimum of these chosen. It is understood that the wear as well as other things must be taken into account in the final choice of an optimum.
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From page 109... ...
the cycle. Thrust is applied to the machine to balance the momentum loss due to the transfer of momentum from the piston to the drill steel.
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From page 110... ...
ing in rock breakage is only about 9%. It would certainly look as though this is a prime area for research.
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From page 111... ...
of improving the efficiency of percussive drilling systems, the major area of improvement, that associated with the primary propulson system has already been done. This is not to say that the manufacturers will not continue to improve the products, however the major step has been taken.
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From page 112... ...
One can increase either the blow frequency or the blow energy to increase the power output. This can be done to a certain extent but very soon materials problems arise due to the stresses produced in the drill steel]
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From page 113... ...
than micro scale. Immediate returns could be obtained by perscribing ranges of optimum operating conditions in various rock types.
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From page 114... ...
operate by applying high thrusts to the bit which,due to the penetration produced, allow the generation of high torques. These in turn allow rotary power to be transmitted to the rock.
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From page 115... ...
and sending the cutting edge aqainst solid rockface. This can often lead to broken and chipped carbide faces.
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From page 116... ...
Generally the thrust contribution to the power is smal] compared to rotary power term.
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From page 117... ...
cuttings removal is also an important problem here and should be given some attention. It is felt that the present major limitation to the greater use of rotary drilling is that imposed by the bit.
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From page 118... ...
~~ i RP 2mNt + TR + BPM x ER where Pip The effect of varying the parameters is much more difficult power output to assess. For example an increase in the blow energy could conceivably decrease the torque generated and lead to a total decrease in the applied power.
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From page 119... ...
production machine into this country in 1962 for trials and had initial problems with bit and steel life. The author is not familiar with the present situation at St.
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From page 120... ...
replied, "I increase it until the bits begin to break and then back off a little". With the increasingly wide spread use of hydraulic systems, sufficient power is available to remove rock at very high rates.
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From page 121... ...
at which tools should be changed. Worn tools, in addition to giving poor advance rates can produce damage to the machine and operator fatigue.
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From page 122... ...
indicated only a small effect, if any. It would seem reasonable to expect that certain additives should change the difficulty with which a surface layer can be removed by a cutting tool.
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From page 123... ...
Positioning can be done by the coordinate method however there are some inherent disadvantages to this (122)
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From page 124... ...
have been eliminated. However, there still remains the noise of the piston striking the drill steel, the steel against the rock, and the noise associated with the hydraulic motor.
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From page 125... ...
as positive factors in underground work. These positive factors can be jeopardized by extensive mechanization and automation.
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From page 126... ...
this trend have come some very real improvements in bolting technology. The principal advances to date have been in (1)
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