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Bureau of Mines Information Circular/1987 
 
 Test Apparatus for Measuring 
 Sound Power Levels of Drills 
 
 By William W. Aljoe, Robert R. Stein, 
 and Roy C. Bartholomae 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 

/>j2jfc> j&jj* , jVu^^/j/i^ 
 
 Information Circular 9166 
 
 A 
 
 Test Apparatus for Measuring 
 Sound Power Levels of Drills 
 
 By William W. Aljoe, Robert R. Stein, 
 and Roy C. Bartholomae 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 Donald Paul Hodel, Secretary 
 
 BUREAU OF MINES 
 
 David S. Brown, Acting Director 
 

 
 Library of Congress Cataloging in Publication Data: 
 
 Aljoe, William W. 
 
 Test apparatus for measuring sound power levels of drills. 
 
 (Information circular/United States Department of the Interior. Bureau of Mines; Hltib) 
 
 Bibliography: p. 34-35. 
 
 Supt. of Docs, no.: I 28.27: 9166. 
 
 1. Rock-drills— Noise. I. Stein, Robert R. II. Bartholomae. R. C III Title IV. Series: 
 Information circular (United States. Bureau of Mines): 9166. 
 
 TN295.U4 [TN279] 
 
 622 s 
 
 [622'.8] 87-600273 
 
 
 
CONTENTS 
 
 Page 
 
 Abs t ract 1 
 
 Introduction 2 
 
 Test system considerations 4 
 
 Control of drill operating parameters 4 
 
 Control of the acoustical environment 5 
 
 Data collection and analysis 7 
 
 System description 8 
 
 System operation 12 
 
 Drill test program 12 
 
 Test sequence 12 
 
 Data input and startup procedure 13 
 
 Data collection and display 14 
 
 Control subsystems 15 
 
 IBM-XT microcomputer 15 
 
 Westinghouse PC-700 process controller 15 
 
 Drill rig positioning control 16 
 
 Carriage lock control 16 
 
 Feed thrust and hole depth control 17 
 
 Drill hammer control 18 
 
 Drill rod rotation control X 18 
 
 Flushing water control 20 
 
 Other drill test commands 20 
 
 Hole location program 21 
 
 Selection of hole position 21 
 
 Validation of input data 22 
 
 Selection of hole depth 22 
 
 Data analysis program 22 
 
 Direct data analysis and graphics 23 
 
 Test selection 23 
 
 Raw data retrieval 23 
 
 Basic system graphics 25 
 
 Expanded data analysis through spreadsheets 27 
 
 File conversion procedure 27 
 
 Advantages of spreadsheet analysis 28 
 
 Initial test results 29 
 
 Pneumatic versus hydraulic percussion drills 30 
 
 Rotary versus percussion drills 32 
 
 Discussion 34 
 
 References 34 
 
 ILLUSTRATIONS 
 
 1. Noise sources on typical hand-held percussion drill 2 
 
 2. Noise sources on typical jumbo-mounted percussion drill 3 
 
 3. Typical noise radiation pattern 6 
 
 4. Components of automated drill test fixture and control system 8 
 
 5. Drill test rig in reverberation chamber, top view 10 
 
 6. Drill test rig in reverberation chamber, profile view 10 
 
 7. Drill test rig in reverberation chamber, rear view showing control room.... 11 
 
 8. Drill test rig in reverberation chamber, control valves and process 
 
 sensors 11 
 
 9. Drill test software program selection menu 12 
 
11 
 
 ILLUSTRATIONS— Continued 
 
 Page 
 
 10. Main data input menu for drill test program 
 
 11. Drill rig carriage and boom positioning system 
 
 12. Drill carriage lock system 
 
 13. Feed thrust and hole depth control system 
 
 14. Drill hammer control system 
 
 15. Drill rod rotation control system 
 
 16. Data input menu for hole location program 
 
 17. Data input menu for analysis program 
 
 18. Printout of drill test data 
 
 19. Graphs of hammer pressure, feed thrust, feed rate, and sound power versus 
 
 elapsed time 
 
 20. Sound power spectrum and spectrum waterfall graphs 
 
 21. Data input menu for Spreadsheet Formatter program 
 
 22. Average frequency spectra: pneumatic and hydraulic percussion drills 
 
 23. Frequency spectra for percussion drills, beginning versus end of hole 
 
 24. Average frequency spectra: pneumatic and hydraulic percussion drills, 
 
 pneumatic rotary drill 
 
 25. Frequency spectra for pneumatic rotary drill: beginning versus end 
 
 TABLE 
 
 1. Maximum values and accuracy of ADTF control parameters 
 
 13 
 
 16 
 17 
 17 
 19 
 20 
 21 
 23 
 24 
 
 25 
 26 
 27 
 30 
 31 
 
 33 
 33 
 
 13 
 
 
 UNIT OF MEASURE ABBREVIATIONS 
 
 USED IN 
 
 THIS REPORT 
 
 cfm 
 
 cubic foot per minute 
 
 in/s 
 
 inch per second 
 
 dB 
 
 decibel 
 
 Kb 
 
 kilo byte 
 
 dBA 
 
 decibel, A-weighted 
 
 kHz 
 
 kilohertz 
 
 ft 
 
 foot 
 
 lbf 
 
 pound (force) 
 
 ft 2 
 
 square foot 
 
 Mb 
 
 megabyte 
 
 ft 3 
 
 cubic foot 
 
 min 
 
 minute 
 
 f t/min 
 
 foot per minute 
 
 pet 
 
 percent 
 
 gpm 
 
 gallon per minute 
 
 psi 
 
 pound (force) per 
 square inch 
 
 h/d 
 
 hour per day 
 
 
 
 
 
 s 
 
 second 
 
 Hz 
 
 Hertz 
 
 
 
 
 
 V 
 
 volt 
 
 in 
 
 inch 
 
 
 
TEST APPARATUS FOR MEASURING SOUND POWER LEVELS OF 
 
 DRILLS 
 
 By William W. Aljoe, 1 Robert R. Stein, 1 and Roy C. Bartholomae 2 
 
 ABSTRACT 
 
 This Bureau of Mines report describes in detail the design and opera- 
 tion of a test apparatus for measuring the sound power levels of drills 
 used by the mining industry. The two major components of the test ap- 
 paratus are a computer-controlled automated drill test fixture (ADTF) 
 and a large (45,000-ft 3 ) reverberation chamber that houses the ADTF. 
 Design specifications and performance capabilities of the ADTF and the 
 reverberation room are given. Initial test results for three types of 
 drills — a pneumatic percussion drill, a hydraulic percussion drill, and 
 a pneumatic rotary drill — are given to illustrate the types of experi- 
 ments that can be conducted with the test appartus. 
 
 1 Mining engineer. 
 ^Supervisory electrical engineer. 
 Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
 
INTRODUCTION 
 
 Percussion drills used in the mining 
 industry produce noise that can cause 
 exposures of 10 to 20 times the limits 
 allowed by Federal noise regulations. 
 Typical noise levels experienced by per- 
 cussion drill operators are 110 to 120 
 dBA. Approximately 60, 000 percussion 
 drills are being used in the mining in- 
 dustry (JO, 3 and many more are used in 
 the construction industry. Given the 
 severity of the percussion drill noise 
 problem, it is not surprising that con- 
 siderable efforts have been made toward 
 its control. 
 
 The primary noise-generating mechanism 
 in all percussion drills is the repeated 
 hammering action of an oscillating steel 
 piston on the end of a long, slender 
 striking bar (drill rod). This action 
 causes vibration of both the drill rod 
 and the cylindrical piston housing, 
 thereby producing drill rod noise and 
 drill body noise. On pneumatic drills, 
 the high-pressure air used to oscillate 
 the piston is exhausted to the atmosphere 
 through ports in the drill body, thus 
 producing air exhaust noise. Figure 1 
 depicts these three major noise sources 
 on a typical hand-held pneumatic (stoper) 
 drill. Figure 2 shows the various noise 
 sources associated with a typical 
 machine-mounted (jumbo) drill; however, 
 the drill body, drill rod, and air ex- 
 haust are still by far the most serious 
 noise sources on the drill. 
 
 Numerous attempts have been made in the 
 past by the Bureau of Mines and other re- 
 searchers to control percussion drill 
 noise through the use of retrofit noise 
 control treatments (_2-_6_) and new drill 
 design features (7-10). These attempts 
 have been moderately successful, result- 
 ing in noise reductions of up to 15 dBA 
 at the drill operator position. Unfortu- 
 nately, some of the noise-controlled 
 drills were rather impractical from an 
 operation standpoint (e.g., reduced 
 drilling rates, muffler freezing, exces- 
 sive weight and bulk). 
 
 ■^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this report. 
 
 Pr 
 
 Drill steel 
 
 FIGURE 1. — Noise sources on typical hand-held percussion 
 drill. 
 
Piston-striking bar impact 
 
 Leakage air noise 
 
 Air motor noise 
 ^ , Body noise 
 
 ■ Exhaust noise 
 
 FIGURE 2. — Noise sources on typical jumbo-mounted percussion drill. 
 
 Furthermore, in most cases the quieted 
 noise levels were still above 100 dBA; 
 operator exposure would have to be lim- 
 ited to only 2 h/d to maintain compliance 
 with Federal noise regulations. 
 
 To date, the most effective means of 
 protecting the percussion drill operator 
 from noise overexposure has been to iso- 
 late him or her from the noise source by 
 using an acoustical cab. Noise reduc- 
 tions of up to 20 dBA have been achieved 
 through this technique, and in several 
 cases the noise level measured inside the 
 cab was below 90 dBA (6). Acoustical 
 cabs can be applied most successfully to 
 machine-mounted drills that are used in 
 areas of unrestricted headroom or where 
 remote control of drill positioning and 
 operation is employed. However, many 
 mining situations require the use of 
 small hand-held drills because of space 
 limitations; this precludes the use of 
 acoustical cabs. In fact, the hand-held 
 percussion drill remains the bulwark of 
 
 many underground ore mining operations 
 because of its compactness, flexibility, 
 reliability, and low cost. Space limita- 
 tions and interference with drill opera- 
 tion (e.g., operator vision) also dis- 
 courage the use of acoustical cabs on 
 many types of jumbo-mounted drills. 
 
 Considering the high-energy nature of 
 percussion drilling, the limited success 
 of previous efforts to control drill 
 noise at its source, and the limited 
 practical application of acoustical cabs, 
 it is doubtful that the majority of per- 
 cussion drill operators will work, in a 
 nonhazardous noise environment in the 
 near future. If the mining industry con- 
 tinues to use percussion drills, even 
 quieted models, as it has in the past, it 
 is reasonable to assume that numerous 
 noise overexposures will occur in the 
 years to come. 
 
 Despite the severity of the percussion 
 drill noise problem and the fact that all 
 percussion drills are inherently noisy, 
 
it is important to note that some drills 
 generate more noise than others. Opera- 
 tor exposure to noise can be reduced by 
 choosing a less noisy drill or drilling 
 system. Factors that can affect the 
 noise produced by a drill include the 
 source of power (air or hydraulic), input 
 energy, degree of wear and leakage, drill 
 rod size and type, hammer and shank con- 
 figuration, means of drill steel rotation 
 (rifle bar or independent), and location 
 of the operator with respect to the 
 drill. The application and effectiveness 
 of noise control techniques are greatly 
 affected by these differences. 
 
 An in-depth understanding of drill de- 
 sign characteristics and their effect on 
 noise is an important part of any effort 
 to reduce the noise problem. The Bureau 
 
 of Mines, while continuing in this en- 
 deavor, does not possess the funding or 
 drill design expertise to embark on a 
 program to develop a drill or drilling 
 system that can solve the problem com- 
 pletely. However, with the aid of the 
 test apparatus described in this report, 
 it is possible for the Bureau to signifi- 
 cantly enhance the body of knowledge on 
 the subject of drilling noise. For ex- 
 ample, the test apparatus can provide 
 valuable but heretofore unavailable quan- 
 titative information on the sound power 
 levels produced by different types and 
 models of drills. Noise variations re- 
 sulting from differences in drill operat- 
 ing parameters can also be investigated 
 and quantified. 
 
 TEST SYSTEM CONSIDERATIONS 
 
 To conduct thorough, systematic studies 
 of drill noise, the researcher needs (1) 
 control of the parameters that affect 
 drill performance, (2) control of the 
 acoustical environment in which the drill 
 operates, and (3) a comprehensive, well- 
 organized data collection and analysis 
 system. The Bureau's test apparatus ful- 
 fills all three of these requirements. 
 
 CONTROL OF DRILL OPERATING PARAMETERS 
 
 The operation of a percussion drill is 
 affected by many parameters such as the 
 composition of the drilling medium, 
 sharpness of the bit, type of bit used, 
 length and type of drill rod, number of 
 rod sections, drill feed force, supply 
 pressure to the drill, wear condition of 
 
 the drill, and hole flushing medium. Un- 
 der actual drilling conditions in the 
 field, control of all these parameters is 
 a very difficult and sometimes impossible 
 task. In short, it can be said that no 
 two holes drilled in the field are ever 
 exactly the same. 
 
 In the laboratory, however, it is pos- 
 sible to control these parameters such 
 that any drilled hole is repeatable. 
 More importantly, it is possible to se- 
 lectively change only one parameter from 
 hole to hole to determine its effect on 
 noise and penetration rate. The computer 
 controlled automated drill test fixture 
 (ADTF) facilitates this process by auto- 
 matically maintaining the supply pres- 
 sure, rotation flow, and feed force spec- 
 ified by the user. These parameters can 
 
also be changed by the user during the 
 course of a test if desired. The ADTF 
 
 also allows the user to select an exact 
 hole location (following a preprogrammed 
 pattern), hole depth, and drill power 
 source (air or hydraulic) for each test. 
 
 The ADTF achieves this control through 
 the use of standard, commercially- 
 available hardware such as pressure, 
 flow, and position transducers, a pro- 
 grammable process controller, and a desk- 
 top microcomputer. Software designed 
 specifically for the purpose of drill 
 test provides the user with continuous 
 on-line information and interactive capa- 
 bility via the computer's cathode ray 
 tube and keyboard. Safety is ensured by 
 the presence of several types of auto- 
 matic and user-initiated shutdown modes. 
 
 By conducting drill noise tests in the 
 laboratory, it is also possible to exer- 
 cise almost complete control of the 
 drilling medium, bit type and sharpness, 
 drill rod length and type, and hole 
 flushing medium. These parameters can 
 almost never be changed or controlled in 
 the field due to local geology, blasthole 
 size requirements, and other production 
 considerations. The capability of pro- 
 viding a relatively homogeneous drilling 
 medium (precast concrete or precut gran- 
 ite) is particularly advantageous when 
 assessing the effect of other drilling 
 parameters on drill penetration rate. 
 
 CONTROL OF THE ACOUSTICAL ENVIRONMENT 
 
 The acoustical environment of an oper- 
 ating mine is rarely consistent because 
 the extent of the mine and the location 
 of the noise sources change almost daily 
 as mining progresses. 
 
 Irregular reflecting surfaces are often 
 present, and extraneous noise sources 
 (other pieces of mining equipment) add to 
 the difficulty of measuring the noise 
 produced by a drill. Microphone location 
 
 is another important factor to consider 
 when measuring drill noise in the field 
 because the sound pressure can vary 
 greatly from point to point within the 
 area of interest. Measurement of drill 
 noise in the laboratory allows for con- 
 trol of some of these variables, but the 
 experimental environment must be chosen 
 carefully to assure that useful noise in- 
 formation is obtained in a practical and 
 cost-effective manner. 
 
 The two fundamental properties that de- 
 fine the noise-radiating capability of a 
 sound source are its sound power and di- 
 rectional characteristics. Sound power 
 is a measure of the rate at which acous- 
 tical energy is emitted by a noise 
 source; it is usually expressed as sound 
 power level, in decibels (dB), by the 
 formula 
 
 PWL = 10 log (W ac + /W ref ), 
 
 where PWL = sound power level, dB, 
 
 W act = actual sound power, w, 
 
 and W re f = reference sound power, 
 10~ 12 w. 
 
 The most important distinction between 
 sound power level and sound pressure 
 level, the quantity most commonly asso- 
 ciated with noise, is that sound power 
 is a fundamental property of the noise 
 source itself. Conversely, the sound 
 pressure level is dependent on the 
 distance from the noise source, the 
 direction from the source, and the acous- 
 tical properties of the environment in 
 which it is measured. The relationship 
 between sound pressure and sound power 
 levels can be quantified (11): 
 
 SPL = PWL + 10 log [(Q/4 a r 2 )+(4/ a S)] 
 + 10, 
 
where SPL = sound pressure level at any 
 given point in an 
 environment , dB , 
 
 PWL = sound power level of noise 
 source, dB , 
 
 Q = directivity factor (dimen- 
 sionless) of the source, 
 whose value is dependent 
 on the angle from the 
 acoustical center of the 
 source to the measurement 
 point, 
 
 r = distance from the source, 
 ft, 
 
 a = average absorption coeffi- 
 cient (dimensionless ) of 
 the acoustical environment, 
 including its boundaries 
 and objects located within 
 it, 
 
 and S - total surface area, ft 2 , of 
 all reflecting surfaces 
 within the environment. 
 
 For the drill noise research program 
 envisioned by the Bureau of Mines, sound 
 power is the quantity of greatest inter- 
 est because (1) it allows direct noise 
 comparisons to be made among different 
 types and models of drills, and (2) it 
 can be used to predict the sound pressure 
 levels that will occur in other envi- 
 ronments, given their acoustical 
 characteristics. 
 
 The directional property of a sound 
 source describes its tendency to radiate 
 more noise in one direction than in 
 others. Directional properties are usu- 
 ally displayed in a graphical form called 
 a radiation pattern (fig- 3), showing 
 sound pressure level at a fixed distance 
 from the source as a function of angle. 
 It should be noted that figure 3 is for 
 illustrative purposes only; the sound 
 pressure levels in the figure do not cor- 
 respond to measured values for an actual 
 drill. 
 
 From a purely diagnostic standpoint, 
 the most complete characterization of any 
 noise source can be obtained by isolating 
 it in an anechoic (free field) environ- 
 ment, i.e., one in which no reflections 
 
 50 c 
 
 ANGLE FROM NOISE SOURCE 
 60° 70° 80° 90° 100° 110° 120° 
 
 I30 ( 
 
 UJ 
 
 
 o 
 
 
 a: 
 
 
 ID 
 O 
 
 40° 
 
 CO 
 
 
 UJ 
 
 
 CO 
 
 
 o 
 
 30° 
 
 2 
 
 
 S 
 
 
 o 
 
 20° 
 
 u_ 
 
 
 iii 
 
 
 _i 
 
 10° 
 
 o 
 
 
 z 
 
 
 < 
 
 0° 
 
 100 
 
 90 80 Noise source 80 90 
 
 SOUND PRESSURE LEVEL, dB 
 
 FIGURE 3.— Typical noise radiation pattern. 
 
 100 
 
occur and no other noise sources are 
 present. By measuring the sound pressure 
 at numerous points on a series of imagin- 
 ary spheres located at various radial 
 distances from the geometric center of 
 the noise source, it is possible to 
 determine both the sound power and the 
 directional properties of the source. 
 Unfortunately, this experimental approach 
 could not be pursued by the Bureau of 
 Mines because it would have been prohibi- 
 tively expensive, time consuming, and 
 impractical. 
 
 In terms of cost, practicality, and the 
 ability to obtain useful information on 
 drill noise, the Bureau of Mines deter- 
 mined that the reverberant environment 
 was the best environment to choose. An 
 important feature of a perfectly rever- 
 berant environment is that the sound 
 pressure levels at all points are the 
 same due to the multitude of sound re- 
 flections that occur at its boundaries 
 (walls). If only one dominant sound 
 source is present in the environment, its 
 sound power level can be calculated easi- 
 ly by comparing the measured sound pres- 
 sure levels to those produced by a refer- 
 ence source of known sound power. Most 
 importantly, it was possible to con- 
 struct, at a reasonable cost, a reverber- 
 ant environment (reverberation chamber) 
 capable of housing a full-sized drill 
 test fixture. In addition, the instru- 
 mentation needed to automatically calcu- 
 late drill sound power levels was afford- 
 able, the test procedures involved with 
 this setup were relatively simple, and 
 useful results could be obtained within a 
 reasonable time frame. 
 
 The greatest disadvantage of testing 
 drills in a reverberant environment is 
 the inability to determine the direction- 
 al nature of the noise source. The lack 
 of directional information makes it more 
 difficult to assess the relative noise 
 contributions of the drill rod, drill 
 body, and air exhaust. Also, potential 
 
 noise reductions that could result from 
 the judicious selection of the drill 
 operator position or the insertion of 
 partial acoustical barriers between the 
 drill and the operator cannot be de- 
 tected. This disadvantage can be over- 
 come by conducting supplemental tests in 
 a semifree field (outdoors) with drills 
 that exhibit particularly strong direc- 
 tivity patterns. 
 
 DATA COLLECTION AND ANALYSIS 
 
 Collection of drilling data in the 
 field usually requires substantial human 
 effort such as constant visual monitoring 
 of pressure gauges, flowmeters, stop- 
 watches, etc. Noise monitoring in the 
 field is often performed only with hand- 
 held sound level meters. Extensive, 
 careful notes must be maintained to make 
 sure the data are recorded completely and 
 correctly. Even when data are recorded 
 electronically (strip chart recorders, 
 data loggers, or magnetic tape), consid- 
 erable human intervention is needed to 
 assemble and correlate the data for later 
 analysis. 
 
 The computer-controlled ADTF is the 
 ideal means for simplifying the task of 
 data collection and analysis. Signals 
 from permanently installed transducers 
 for flow, pressure, and position are con- 
 verted by the ADTF software into standard 
 units (cfm, psi, etc. ) and are recorded 
 on a floppy disk at 4-s intervals. Sound 
 power levels are recorded at 18-s inter- 
 vals, and a continuous record of time 
 elapsed during the test allows for auto- 
 matic correlation of all test parameters. 
 All other information pertinent to the 
 test (drill type, hole size and location, 
 drill rod and bit type, etc. ) is also 
 recorded on disk, and the computer as- 
 signs a specific test number to the en- 
 tire block of test data. This greatly 
 facilitates posttest analysis and 
 comparisons among different tests. 
 
SYSTEM DESCRIPTION 
 
 The drill noise test apparatus consists 
 of eight distinct components, shown sche- 
 matically in figure 4: 
 
 1. A microcomputer (IBM model PC -XT, 4 
 referred to as the XT) with hard-disk 
 storage of menu-driven programs for drill 
 operation and data analysis. 
 
 2. A programmable process controller 
 (Westinghouse PC-700, referred to as the 
 PC) with control cards for input, output, 
 and high-speed counting functions. 
 
 3. A 15-ft-long by 9-ft-wide by 
 6-ft-high drill test rig consisting of 
 
 ^Reference to specific products does 
 not imply endorsement by the Bureau of 
 Mines. 
 
 (a) a rubber-tired carriage, (b) a pivot- 
 ing boom with two 10-ft-long feed chan- 
 nels, (c) the drills themselves, and (d) 
 the hydraulic and pneumatic control 
 valves and transducers. Figures 5-8 show 
 several views of the drill test rig and 
 drilling medium. The valves and trans- 
 ducers (fig. 8) are designed to meet the 
 capacities of the hydraulic and pneumatic 
 power sources listed in items 6 and 7 
 below. 
 
 4. Valve driver cards (manufactured by 
 Ledex, Inc. , and referred to as the Ledex 
 drivers) needed to operate some of the 
 larger hydraulic control valves that re- 
 quire a 24-V input potential. 
 
 Control 
 room 
 
 O 
 
 o o 
 
 r 
 
 Hydraulic power supply 
 control box 
 
 [—Hydraulic power supply 
 control cable 
 
 I | /-Micro- 
 Z~~_ computer 
 
 ff 
 
 Process controller (PC) 
 
 1- 
 
 ¥ 
 
 ± 
 
 Sound-measuring instrumentation 
 
 Frequency-to-analog 
 converter cards 
 
 2l 
 
 High-speed counters 
 Output cards 
 Input cards 
 
 J-±I5.8-V power supply \J 
 
 5-V power supply 
 / — PC output cable 
 
 24-V 
 
 power 
 
 supply 
 
 -Test chamber 
 (reverberation 
 room) 
 
 Valve-driver and PC output cables 
 
 t: 
 
 A 
 
 Input signal cable Water supply 
 
 FIGURE 4. — Components of automated drill test fixture and control system 
 
 Hydraulic lines (2) 
 -Compressed air line 
 
 Hydraulic power supply 
 
5. A sound measurement system consist- 
 ing of an array of microphones suspended 
 from the ceiling of the reverberation 
 room and instrumentation to calculate 
 sound power levels. Figure 7 shows some 
 of the sound measuring instrumentation in 
 the control room adjacent to the rever- 
 beration chamber. 
 
 6. A remotely controlled hyraulic 
 power source capable of providing up to 
 35 gpm of flow at 5,000-psi pressure. 
 This is sufficient to operate most cur- 
 rently available hydraulic percussion 
 drills. 
 
 7. A compressed air source capable of 
 providing 1,200 cfm of flow at 100-psi 
 pressure. This is sufficient to operate 
 most currently available pneumatic drills 
 with the exception of down-the-hole 
 drills. 
 
 8. A flushing water source for dust 
 suppression. 
 
 The first four components combine to 
 form the automated drill test fixture 
 (ADTF); the other four provide vital sup- 
 port functions and are accessed by the 
 ADTF during its operation. The drilling 
 rig and microphones are located inside 
 the reverberation chamber, the XT and 
 sound measuring instrumentation are lo- 
 cated inside the control room adjacent to 
 the chamber, and the PC and valve drivers 
 are located in cabinets immediately out- 
 side both the test chamber and control 
 room. The hydraulic power pack and air 
 compressor are located remotely so that 
 their noise contribution to the test 
 chamber is minimal. 
 
 All eight components are required for 
 the operation of pneumatic drills, and 
 all but the air compressor are required 
 for hydraulic drills. Although two 
 drills can be mounted on the ADTF at 
 once, only one drill at a time can be 
 operated. The advantage of having two 
 feeds is that a pneumatic and hydraulic 
 drill can operate in consecutive tests 
 
 without having to dismantle and reconnect 
 numerous fluid supply connections. Both 
 percussive-rotary and all-rotary drills 
 can be tested on the ADTF using the same 
 test program and procedures. 
 
 The primary drilling medium consists of 
 two 6- by 6- by 12-ft concrete blocks 
 (compressive strength approx. 6,000 psi) 
 inserted into the chamber wall; see fig- 
 ures 5 and 6. Provision has also been 
 made to drill into granite or another 
 drilling medium either by replacing the 
 concrete or by inserting the medium into 
 the wall between the two concrete blocks. 
 All drilling takes place in the horizon- 
 tal direction, with a maximum depth of 12 
 ft governed by the confines of the build- 
 ing in which the reverberation chamber is 
 housed. 
 
 The reverberation chamber and sound 
 measurement system meet the criteria of 
 ANSI SI. 31-1980, "Precision Methods for 
 the Determination of Sound Power Levels 
 of Broad-Band Noise Sources in Reverbera- 
 tion Rooms." The chamber itself is 60 ft 
 long by 34 ft wide by 22 ft high and is 
 constructed of filled concrete block with 
 nonabsorptive paint covering its interior 
 surfaces. Exhaust fans and floor drains 
 provide a clean working environment with 
 consistent acoustical properties. The 
 sound measurement system consists of (1) 
 an array of 20 randomly spaced micro- 
 phones positioned at 9 to 11 ft above the 
 chamber floor, (2) two 8-channel multi- 
 plexers (Bruel & Kjaer model 2811) to 
 provide access to 16 of the 20 micro- 
 phones during any single test, and (3) a 
 Bruel & Kjaer model 7507 sound power 
 calculator. Alternatively, if sound 
 pressure rather than sound power were the 
 desired quantity, a Bruel & Kjaer model 
 2131 digital frequency analyzer could 
 serve as the third component of the sound 
 measuring system. This system was 
 qualified using the test procedures in 
 section 8 of the ANSI SI. 31-1980. 
 
10 
 
 FIGURE 5.— Drill test rig in reverberation chamber, top view. 
 
 FIGURE 6.— Drill test rig in reverberation chamber, profile view 
 
11 
 
 FIGURE 7.— Drill test rig in reverberation chamber, rear view showing control room. 
 
 
 FIGURE 8. — Drill test rig in reverberation chamber, control valves and process sensors. 
 
12 
 
 SYSTEM OPERATION 
 
 The operator activates the drill test 
 system by turning on the process control- 
 ler (PC), the sound power measurement 
 system, and the microcomputer (XT). 
 Turning on the XT with no floppy disk in 
 place automatically loads the disk oper- 
 ating system (DOS) from the hard disk. 
 At the DOS prompt, the operator loads the 
 drill test software and is presented with 
 the menu shown in figure 9.5 The func- 
 tion keys Fl through F6 on the XT key- 
 board are used to access the various op- 
 tions. The three major elements of the 
 drill test software — the drill test pro- 
 gram, analysis program, and hole location 
 program — are described in this section. 
 
 DRILL TEST PROGRAM 
 
 Test Sequence 
 
 Prior to running a drill noise test, 
 the operator starts the hydraulic power 
 pack and air compressor (if required) and 
 adjusts them to operating pressures that 
 are at least as great as those that will 
 be required for the test. A typical 
 drill noise test sequence follows: 
 
 1. The test operator loads the drill 
 test program (Fl in figure 9) and enters 
 descriptive information and control para- 
 meters (set points) into the XT. 
 
 2. The drill test program checks the 
 input values and, if consistent with sys- 
 tem limitations, loads them into the PC 
 along with a command word to start the 
 test. 
 
 3. The PC moves the drilling rig to 
 the selected hole location, locks the 
 carriage, and pauses for an operator com- 
 mand to proceed. When this command is 
 issued, the PC starts the drilling pro- 
 cess, and the sound measurement system is 
 activated. Throughout the test, the PC 
 handles the task of reading the pressure 
 and flow transducers, comparing their 
 values to those of the set points, and 
 
 ^Throughout this report, graphs and 
 menus such as figure 9 have been modified 
 slightly to conform to Bureau of Mines 
 publication standards. 
 
 opening or closing valves to maintain the 
 set points as closely as possible. 
 
 4. When the feed thrust reaches the 
 set point, the XT starts to collect in- 
 formation from the PC at intervals speci- 
 fied by the test operator. It continues 
 to do so until the hole depth reaches the 
 set point or the operator terminates the 
 test. At this point the XT instructs the 
 PC to stop drilling and retract the 
 drill; the sound measurment system is 
 also deactivated, and the data are 
 written to a file on a floppy disk in the 
 A: disk drive unless the operator de- 
 cides the test was invalid. 
 
 5. When the drill reaches its origi- 
 nal, completely retracted position, the 
 system waits for a new test command to be 
 entered into the XT. 
 
 6. The operator either analyzes data 
 from the test just completed or enters 
 new data for another test. If no other 
 tests are needed but data analysis is de- 
 sired for one or more previous tests, the 
 operator exits the drill test program, 
 enters the data analysis program (F2 in 
 figure 9), and calls in the desired test 
 numbers. Pressing the F4 key allows the 
 operator to check the directory of the 
 disk in the A: drive. 
 
 7. If no subsequent tests or data 
 analyses are desired, the operator issues 
 a command that moves the rig to a home 
 position (conveniently located to permit 
 drill maintenance or removal), exits the 
 drill test program, and shuts down the 
 ADTF and power sources. 
 
 Choose option : 
 
 Fl - Drill test program 
 
 F2 - Analysis program 
 
 F3 - Hole location program 
 
 F4 - Directory of tests on A : 
 
 F5 - Edit controls file ff 
 
 F6 - Exit to DOS 
 
 FIGURE 9. — Drill test software program selection menu. 
 
13 
 
 Data Input and Startup Procedure 
 
 Data input begins when the operator en- 
 ters the drill test program and is pre- 
 sented with the menu shown in figure 10. 
 The circled numbers in figure 10 denote 
 the fields in which test data are entered 
 by the operator, as described below: 
 
 Fields 1, 4, 5, 6, and 9 are text en- 
 tries for documentation purposes; they 
 facilitate later analysis but do not di- 
 rectly impact the test itself. 
 
 Field 2, entered as P or H, identifies 
 whether the drill to be tested is pneu- 
 matic or hydraulic. Field 3, entered as 
 1 or 2, identifies the feed channel on 
 which the test drill is mounted. This 
 information allows the appropriate set of 
 control cards in the PC to be activated 
 during the test. 
 
 Fields 7 and 8, respectively, specify 
 the vertical (rows A through N) and 
 horizontal (columns 1 through 36) hole 
 location. Field 3 is also important in 
 this regard because, for the same hole 
 location on the wall, the actual amount 
 of carriage and boom movement is dif- 
 ferent for each feed. The operation of 
 the hole location program is discussed in 
 more detail later in this report. 
 
 Fields 10, 11, 12, and 13 are the main 
 control parameters governing the 
 operation of the drill during the test. 
 
 Input values are assigned the units shown 
 in figure 10. In the case of field 12, 
 rotation flow, the units depend on field 
 2; gpm Is assumed for hydraulic drills 
 and cfm for pneumatic drills. Table 1 
 lists the maximum allowable values of 
 these parameters and the accuracies 
 achieved by the ADTF control system. 
 
 After all data have been entered, the 
 operator presses the F9 function key 
 (fig. 10) to continue the test. The pro- 
 gram checks the input values for confor- 
 mance with the above requirements, issues 
 an error message if this is not the case, 
 and allows the operator to correct the 
 erroneous data. If the inputs are valid, 
 the program loads the input values into 
 
 TABLE 1. - Maximum values and accuracy 
 of ADTF control parameters 
 
 Parameter 
 
 Maximum 
 
 Accuracy 
 
 
 value 
 
 pet 
 
 Hammer pressure 
 
 5,000 psi 
 
 5 
 
 (hydraulic). 
 
 
 
 Hammer pressure 
 
 350 psi 
 
 5 
 
 (pneumatic). 
 
 
 
 
 12,000 lbf 
 
 4 
 
 Rotation flow 
 
 50 gpm 
 
 5 
 
 (hydraulic). 
 
 
 
 Rotation flow 
 
 1,000 cfm 
 
 2 
 
 (pneumatic). 
 
 
 
 Distance drilled... 
 
 144 in 
 
 3 
 
 Executive 
 commands 
 
 Test docu-. 
 mentation 
 
 F I Exit program 
 
 F3 Move platform home 
 
 F9 Start test 
 
 Main menu 
 
 F2 Master reset 
 
 F4 Test without move 
 
 FIO Data analysis 
 
 (D Drill tested : 
 © Hole size : 
 -(ZHD Location : 
 
 (D Pneumatic or hydraulic; 
 ® Drill steel : 
 (D Comments 1 
 
 Date : September 15, 1985 
 Time; 13=18=35 
 Run; XXXX 
 
 (3) Feed = 
 (6) Bit type = 
 
 Control 
 parameters 
 
 ® Operating hammer pressure 
 
 (D) Feed thrust 
 
 @ Rotation flow* 
 
 © Distance drilled 
 
 Set Actual Status 0001 1000 0000 0000 
 
 psi XXXX Test stage 
 
 lbf XXXX Elapsed time .... 
 
 g/cf XXXX Drill frequency .... BPM 
 
 in XXXX Sound power .... dB 
 
 ♦The notation g/cf for rotation flow reflects the 
 fact that flow is measured in gpm for hydraulic 
 drills and cfm for pneumatic drills. 
 
 On-line information 
 
 FIGURE 10.— Main data input menu for drill test program. 
 
14 
 
 the PC, issues a "Ready" message, and 
 prompts the operator to press F9 again. 
 The drilling rig then moves out to the 
 specified hole location, locks itself in- 
 to place with two clamping cylinders, and 
 pauses. The hole location is then 
 checked visually and, if satisfactory, 
 the operator presses F9 a third time to 
 start the drilling process. At any time 
 during the startup procedure or drilling 
 process, the operator can press the [Esc] 
 key, standard on all IBM and IBM- 
 compatible personal computer keyboards, 
 to halt the test and enter new input data 
 into the main menu. A closed-circuit 
 television system enables the operator to 
 monitor the entire sequence from the 
 safety of the control room and allows him 
 or her to terminate the test quickly 
 should problems occur. 
 
 Data Collection and Display 
 
 As soon as the drill test program 
 checks the data input values and finds 
 them to be valid, it opens a file on the 
 XT floppy disk and writes the input data 
 to the file. These drill test files are 
 named "TEST .DAT", with the blank cor- 
 responding to the sequential test number 
 assigned by the drill test program. This 
 four-digit test number is then displayed 
 on the XT video monitor ("Run" in figure 
 10) and is used for all subsequent data 
 retrieval and analysis. 
 
 After drilling has begun, control of 
 the test is maintained by the process 
 controller (PC). As soon as the feed 
 thrust reaches its set point, the XT col- 
 lects data by reading the PC and the 
 sound measuring instrumentation at speci- 
 fied intervals and writing this informa- 
 tion to the floppy disk file. The opti- 
 mum sampling interval for data collected 
 from the PC was found to be 4 s. Shorter 
 intervals are possible but would result 
 in rapid exhaustion of floppy disk space; 
 longer intervals could result in the loss 
 of important test data. The sampling in- 
 terval for sound power data was chosen to 
 be 18 s. This interval allows the multi- 
 plexer to scan 16 microphones for 1 s 
 each and gives the sound power calculator 
 ample time to perform its computations 
 and store the data. These intervals, 
 
 along with the maximum control parameter 
 values listed in table 1, can be changed 
 easily by the test operator. The F5 
 "Edit conrols file" key in figure 9 pro- 
 vides the operator with a menu that 
 enables these changes to be made from the 
 XT keyboard. Selected information is 
 also displayed on the XT video monitor, 
 as shown in figure 10. The data dis- 
 played immediately to the right of fields 
 10 through 13 allow the operator to com- 
 pare the actual values of the control 
 parameters with those of the set points. 
 The lower right section of figure 10 con- 
 tains the following information: 
 
 Status word. — This 16-digit binary 
 number contains information pertinent to 
 the movement and locking of the drill 
 test rig. It changes during the drill 
 movement sequence, with each digit either 
 identifying the status of a particular 
 hardware component critical to this pro- 
 cess (e.g., limit switches open or 
 closed, input parameters valid or not) or 
 issuing a command to proceed to the next 
 step in the movement cycle (e.g., move 
 carriage and boom to set point, lock car- 
 riage). The status word is a valuable 
 troubleshooting aid if the drill rig 
 either fails to move on command or moves 
 incorrectly. 
 
 Test stage. — A string of text charac- 
 ters written to the display on the basis 
 of the status word. The four test stages 
 are collaring (drill rig moving to set 
 point and drill operating before feed 
 thrust reaches set point), testing (data 
 being collected), retracting, and moving 
 home. 
 
 Elapsed time. — The PC timer starts 
 when the feed thrust reaches the set 
 point and ends when the prescribed drill 
 depth is reached. This provides the time 
 base essential for all posttest 
 analysis. 
 
 Drill frequency. — For percussion 
 drills, the number of blows per minute 
 (BPM) can be used to determine if the 
 drill is operating correctly and can also 
 affect the noise frequency spectrum. 
 Drill frequency information is supplied 
 to the PC via an accelerometer mounted on 
 the drilling rig and appropriate signal 
 conditioning equipment. 
 
15 
 
 Overall sound power . — The XT reads 
 this value directly from the Bruel & 
 Kjaer sound power calculator every 18 s, 
 then resets the 7507 and the multiplexers 
 for another sample. The PC is not in- 
 volved in this process. The sound power 
 levels displayed in figure 10 are linear 
 (unweighted) values. Although A-weighted 
 overall sound power levels would be more 
 desirable from a perceptual standpoint, 
 they cannot be obtained directly owing to 
 the recording and calculating techniques 
 used by the 7507.6 A-weighted levels can 
 be obtained, however, through posttest 
 analysis of the linear data. 
 
 Although the XT serves primarily as a 
 data collector during a normal test, the 
 operator can also enter commands in mid- 
 test through the XT keyboard. Most im- 
 portantly, the operator can terminate a 
 test at any time. It is also possible to 
 change one or more of the control para- 
 meters in fields 10 through 13 by typing 
 new values in the appropriate field(s) 
 and pressing the F9 key. The program 
 responds with a message "New Parameters 
 Sent" on the monitor, and the XT records 
 the values and the time they were sent. 
 This capability is especially advanta- 
 geous because it minimizes the number of 
 holes needed to establish the optimum set 
 of operating parameters (i.e., the set 
 that yields the maximum penetration rate) 
 for a particular drill. 
 
 A typical drill test requires approxi- 
 mately 1,000 bytes of floppy disk space 
 per foot of hole. Therefore, data from 
 at least 30 tests (all 12-ft holes) can 
 be contained on a single 360-kb floppy 
 disk. Larger numbers of tests with shal- 
 lower hole depths can also be retained on 
 a single disk. Data collection and anal- 
 ysis is discussed later in this report. 
 
 6 The A-weighting process simulates the 
 response of the human ear to sounds of 
 various frequencies. The 7507 can record 
 the desired 1 /3-octave band sound power 
 levels only in the linear mode, so the 
 subsequent calculation of the overall 
 sound power level yields a linear value. 
 
 Control Subsystems 
 
 As described above, the ADTF consists 
 of four major elements — the IBM-XT micro- 
 computer, Westinghouse PC-700 process 
 controller, Ledex valve drivers, and the 
 various transducers and control valves on 
 the drilling rig. This section describes 
 how these elements function as a unit to 
 provide the required control of the 
 drilling process. 
 
 IBM-XT Microcomputer 
 
 The IBM-XT is a standard model with a 
 360-kb floppy disk drive, a 10-Mb hard 
 disk drive, a 256-kb random access memory 
 (RAM), and a serial port for communica- 
 tions with the PC-700. All the drill 
 test software is permanently installed on 
 the hard disk. Other add-on cards are 
 installed for (1) a color monitor and 
 graphics printer, (2) programming the PC- 
 700, (3) interfacing with the Bruel & 
 Kjaer sound measuring instrumentation, 
 and (4) a real-time clock and calendar 
 function. 
 
 Westinghouse PC-700 Process Controller 
 
 The PC-700 has a 4, 136-kb memory and 
 can address 32 analog inputs, 32 analog 
 outputs, 256 discrete inputs, and 256 
 discrete outputs. The ADTF system uses 
 14 analog inputs, 12 analog outputs, 4 
 discrete inputs, and 16 discrete outputs. 
 The drill operating information is passed 
 to and from the PC via analog input 
 cards, two analog output cards, one dis- 
 crete input card, one discrete output 
 card, and four high-speed counter cards. 
 Four frequency-to-analog converter cards 
 are also located in the PC-700 cabinet; 
 although these are not addressed directly 
 by the PC, they are essential for PC con- 
 trol of flow-based processes. Power is 
 supplied by three sources — a 5-V supply 
 for the high-speed counters, a 15. 8-V 
 supply for the input and output cards, 
 and a 5-V supply for the frequency- 
 to-analog converters. 
 
16 
 
 All inputs such as transducer signals 
 and control set points from the XT are 
 converted to digital values and stored in 
 selected memory cells called holding reg- 
 isters. During operation, the PC 
 achieves process control by comparing the 
 actual values in the holding registers 
 with those of their corresponding set 
 points. Based on the difference between 
 the actual and set point values, the PC 
 program writes digital values to its out- 
 put registers, which in turn activate the 
 appropriate valves, valve drivers, or 
 counters on the drill test rig. Also 
 contained in the holding registers are 
 values that control the rates at which 
 the output registers are changed; this 
 allows smoother operation of the drills 
 and drilling rig. 
 
 Drill Rig Positioning Control 
 
 The control elements for carriage and 
 boom movement are shown in figure 11. 
 During initial startup, the PC moves the 
 carriage and boom to the zero position, 
 where the limit switches on the drilling 
 rig are closed mechanically. Closure of 
 the limit switches resets the PC's high- 
 speed counters with actual values of zero 
 and reference values corresponding to the 
 set points previously entered into the 
 
 XT. Based on the PC's comparison between 
 the information provided by the position 
 transducer (100 counts per inch input to 
 the high-speed counter) and the count 
 corresponding to the set point, the car- 
 riage smoothly accelerates to its maximum 
 speed, then decelerates as it approaches 
 the set point position. After this posi- 
 tion is reached, the PC nulls the Ledex 
 driver card (input to Ledex of 4 V), thus 
 closing the hydraulic control valve, and 
 locks out the high-speed counter to make 
 sure it does not change during the test. 
 The above sequence is then repeated for 
 the boom. After a test is completed and 
 a new hole location is selected, the car- 
 riage and boom move to the new position 
 without moving to the zero position. 
 
 Carriage Lock Control 
 
 The carriage lock-unlock system, shown 
 in figure 12, is somewhat simpler than 
 the positioning system in that the PC is- 
 sues only an on-off command to the hy- 
 draulic control valve. The two horizon- 
 tal locking cylinders in the carriage 
 guide rail and the vertical foot jack 
 (fig. 7) are connected in parallel to ex- 
 tend and retract simultaneously. Prior 
 to a carriage move, the PC sets the ap- 
 propriate bits in the discrete output 
 
 Position 
 trans- 
 ducer 
 
 100 counts /in 
 
 High-speed 
 counter 
 
 Limit switch 
 
 or 24 V 
 
 Digital 
 
 signal out 
 
 0-818 
 
 Analog 
 
 signal 0"24Vi 
 out 
 0-8 V 
 
 Input from boom valve driver, p q Down 
 similar to that of carriage 
 valve driver 
 
 X 
 
 Up 
 
 LI 
 
 Carnage 
 
 position 
 
 motor 
 
 Boom lift 
 cylinder 
 
 FIGURE 11.— Drill rig carriage and boom positioning system. 
 
17 
 
 card to activate the "unlock" side of the 
 hydraulic valve and deactivate the "lock" 
 side. The reverse takes place after the 
 carriage and boom have reached their set 
 points, thereby locking the rig in place 
 for the test. A timer loop in the PC 
 program delays execution of further steps 
 
 V off, 24 V unlock 
 
 PC 
 
 Bit set n 
 
 a 
 
 Discrete 
 
 output 
 
 card 
 
 Hydraulic 
 
 control 
 
 valve 
 
 
 V off, 24 V lock 
 
 Locking 
 cylinders 
 
 \tp 
 
 Foot jack 
 cylinder 
 
 ffi 
 
 FIGURE 12. — Drill carriage lock system. 
 
 until the locking or unlocking process is 
 completed. 
 
 Feed Thrust and Hole Depth Control 
 
 The feed thrust and hole depth are con- 
 trolled by the pressure and flow, respec- 
 tively, of hydraulic oil in the feed cyl- 
 inder. The upper portion of figure 13 
 diagrams the feed thrust control, and the 
 lower part describes the depth control. 
 
 Since the area of the feed cylinder 
 piston is fixed, the feed thrust is pro- 
 portional to the hydraulic pressure on 
 the larger (head) side of the piston. 
 The pressure transducer in figure 13 
 sends a voltage signal to an analog input 
 card, which in turn assigns a digital 
 value to a holding register in the PC. 
 During drilling, the PC program compares 
 this value to the set point and, depend- 
 ing on whether the pressure needs to be 
 increased or decreased, assigns an appro- 
 priate digital value to an analog output 
 card. The voltage at the output card is 
 sent to the Ledex driver, which increases 
 or decreases the current to the "Forward" 
 side of the hydraulic control valve. 
 This side of the valve then opens or 
 closes to increase or decrease the pres- 
 sure on the head side of the piston. The 
 digital output of the PC is constrained 
 within a relatively narrow range during 
 the drilling mode to prevent the feed 
 
 Pressure 
 transducer 
 
 Feed 
 pressure 
 
 ^> 
 
 Analog 
 input card 
 
 Volts (l~5 V) = pressure r-| Digital data 
 
 Data input 
 
 Total flow 
 counts 
 
 Flow- 
 meter 
 
 Feed 
 flow 
 
 Pulses = flow (38/in) 
 
 dJ 
 
 Limit 
 switch 
 
 High-speed 
 counter 
 
 Off (open), on (closed) 
 
 (Feed retracted) 
 
 Bit set 
 
 Discrete 
 input card 
 
 Digital output 
 413 = null n 
 
 300 V= 
 retract 
 
 24 V 
 
 -24 V f 
 
 Forward 
 
 0-8V 
 
 4 V= null 
 
 Analog 
 output card 
 
 Discrete 
 output card 
 
 Reset counter signal 
 
 Valve 
 driver 
 
 ; t „ 
 
 X Hydraulic 
 *-L valve 
 
 ? 
 
 5 V = retract-^ 
 
 Feed cylinder _Jo) 
 
 Forward — ~ 
 — Retract 
 
 FIGURE 13.— Feed thrust and hole depth control system. 
 
18 
 
 from lurching forward at the start of 
 drilling, when the actual and set point 
 pressures are far apart. A dead band 
 around the set point is also included to 
 prevent the feed pressure from oscillat- 
 ing rapidly when the actual and set point 
 pressures are very close but not 
 identical. 
 
 Hole depth is measured and controlled 
 by the flow of hydraulic oil through a 
 positive-displacement flowmeter in the 
 line leading to the head side of the feed 
 cylinder. This flowmeter generates 38 
 voltage pulses per inch of feed travel, 
 which are transmitted to the high-speed 
 counter. The counter tallies the pulses 
 and assigns the total count during a test 
 to a PC holding register for comparison 
 with the count corresponding to the drill 
 depth set point. A normal test ends when 
 the two counts are equal; at this point 
 the XT commands the PC to stop drilling 
 and retract the feed. 
 
 To initiate the retraction phase, the 
 PC sends a digital value of 300 to the 
 analog output card, which then sends an 
 input voltage of 3 V to the Ledex driver. 
 The subsequent Ledex output is 5 V to the 
 "Retract" side of the hydraulic control 
 valve. This causes oil to flow to the 
 rod side of the feed piston at a slow, 
 constant rate to retract the drill. When 
 the drill reaches the fully retracted 
 position, the limit switch on the feed 
 (fig. 6) closes mechanically. The PC 
 then sends a null value (413) to the ana- 
 log output card, thus stopping the feed, 
 and sends a discrete output to the high- 
 speed counter to zero the actual count 
 for the next test. 
 
 Pressure control for hydraulic hammers 
 involves the same basic sequence as feed 
 thrust control. Voltage from a pressure 
 transducer is converted to a digital sig- 
 nal and compared to the set point in the 
 PC, which assigns an output that eventu- 
 ally results in the opening or closing of 
 a hydraulic valve. In the case of hammer 
 pressure, only one side of the valve is 
 activated because a reverse hammer func- 
 tion is not required. As with feed pres- 
 sure, the PC's digital output range is 
 limited to prevent hammer pressure 
 surges, and a dead band around the set 
 point is included. 
 
 Pressure control for pneumatic hammers 
 includes the same type of analog input 
 and PC comparisons as for hydraulic ham- 
 mers, but the output involves three dis- 
 crete control circuits. One circuit 
 serves only to turn the main air supply 
 valve on or off, as determined by the 
 pneumatic-hydraulic choice entered into 
 the XT (field 2 of figure 10). The other 
 two circuits operate the pilot valve that 
 controls the pressure-regulating valve 
 (figure 14). After the PC compares the 
 actual pressure to the set point, it 
 opens one side of the pilot valve and 
 closes the other. If the actual pres- 
 sure is less than the set point, the PC 
 opens the side that increases the pres- 
 sure in the regulating valve. If the 
 actual pressure is greater than the set 
 point, the PC opens the opposite side of 
 the pilot valve, reducing the pressure in 
 the regulating valve. Reaction time of 
 this system is very rapid and a dead band 
 is included, so the amount of air vented 
 to the atmosphere is minimal. 
 
 Drill Hammer Control 
 
 Drill Rod Rotation Control 
 
 Two different types of drill hammer 
 control systems are shown in figure 14; 
 the top portion describes the analog con- 
 trol system for hydraulic drills, and the 
 lower part shows the discrete control 
 system for pneumatic drills. The two 
 systems are similar in that pressure is 
 used as the process control variable, 
 with flow being recorded in the PC for 
 informational purposes only. However, 
 the method for controlling pressure is 
 somewhat different, as described below. 
 
 Drill rod rotation control (fig. 15) is 
 very similar to hammer control for pneu- 
 matic and hydraulic drills, as can be 
 seen by comparing figures 14 and 15. The 
 major difference is that flow rather than 
 pressure serves as the process control 
 variable, with pressure being recorded 
 for informational purposes only. Flow is 
 the preferred control variable for rota- 
 tion because the load on the rotation 
 motor varies considerably during the 
 course of a test (collaring, drilling, 
 
19 
 
 Pressure Analog 
 
 transducer Volts (l"5V) input card 
 = pressure 
 
 Hammer 
 pressure 
 
 O 
 
 Hammer 
 flow 
 
 Control L^d data 
 input values 
 
 Frequency n 
 
 = flow Data 
 
 — I n input 
 
 Flow 
 transducer 
 
 Digital 
 data 
 
 Volts (l"5V) = flow 
 
 Frequency- 
 to-analog 
 converter card 
 
 Digital output 
 409-818 „ 
 
 PC 
 
 Analog 
 output card 
 
 HYDRAULIC DRILL SYSTEM 
 
 0-24 V 
 
 4-8 V 
 
 Hydraulic 
 drill 
 
 Valve 
 driver 
 
 Hydraulic 
 
 control 
 
 valve 
 
 Hammer 
 pressure 
 
 Pressure Ana|og 
 
 transducer Vo | ts (|- 5V ) input card 
 
 = pressure 
 
 Control and data 
 input values 
 
 o 
 
 Frequency 
 = flow 
 
 Hammer 
 flow 
 
 Data 
 input 
 
 Digital data 
 
 PC 
 
 Discrete 
 output card 
 
 On- off bit 
 command 
 
 V off, 24 V on 
 
 V off, 
 
 24 Von 
 
 (decrease 
 
 pressure) 
 
 Volts (l"5V) = flow 
 
 V off, 
 24 V on 
 (decrease 
 pressure) 
 
 Flow 
 transducer 
 
 Frequency- 
 to-analog 
 converter card 
 
 PNEUMATIC DRILL SYSTEM 
 FIGURE 14.— Drill hammer control system. 
 
 Supply air 
 
 Air supply 
 valve 
 
 Pneumatic 
 drill 
 
 Zl 
 
 Pressure- 
 regulating 
 valve 
 
 Pilot valve 
 
 and retracting modes). Flow changes re- 
 sulting from motor load changes are much 
 smaller in magnitude than the associated 
 pressure fluctuations, thus making a 
 flow-based control system more 
 desirable. 
 
 Input signals are generated in the 
 form of voltage pulses from turbine 
 flowmeters, converted to analog signals 
 by the frequency-to-analog cards, and 
 sent to the PC via analog input cards. 
 Output signals are generated by the PC 
 based on the difference between the ac- 
 tual flows and the set points. For hy- 
 draulic rotation, the "Forward" side of 
 the rotation valve is opened or closed 
 proportionally via the Ledex driver to 
 increase or decrease rotation flow. For 
 pneumatic rotation, the pilot valve pres- 
 sure regulating system described for 
 pneumatic hammers is employed; in this 
 case flow control is achieved through 
 pressure changes. 
 
 Another difference between the hammer 
 and rotation control systems is that re- 
 verse rotation is possible, although for- 
 ward and reverse rotation cannot be 
 achieved during the same drill test. Re- 
 verse rotation can be obtained simply by 
 reversing the hose connections to the 
 rotation motor. 
 
 Rotation flow is also monitored by the 
 XT to serve as a safety shutdown during 
 the drilling and retracting phases of a 
 test. A rotation flow of zero indicates 
 a stuck bit, which could cause damage to 
 the bit, drill rod, and perhaps the drill 
 itself. If the flow goes to zero during 
 the drilling phase, the test is aborted 
 and the retraction phase initiated. If 
 the flow remains zero (unsuccessful re- 
 traction), the PC goes into a null state 
 to allow the stuck bit to be freed by 
 hand. 
 
20 
 
 Pressure Analog 
 
 transducer Vo | ts (|- 5 v) j nput card 
 
 = pressure 
 
 Rotation 
 pressure 
 
 Data input 
 
 C^ 
 
 Rotation 
 flow 
 
 Frequency Control 
 = flow ' and data 
 input 
 
 Digital data 
 
 PC 
 
 Digital output 
 0-818 m 
 
 0-24 V 
 
 Flow 
 transducer 
 
 Volts (1-5 V) = flow 
 
 Frequency- 
 to-analog 
 converter card 
 
 0-8V 
 
 Ana og 
 output card 
 
 HYDRAULIC DRILL SYSTEM 
 
 Valve 
 driver 
 
 ^Hydraulic 
 O,cor 
 
 ? 
 
 control 
 valve 
 
 0-24 V 
 
 Hydraulic 
 
 rotation 
 
 motor 
 
 Pressure Analog 
 
 transducer Volts (l"5V) input card 
 = pressure 
 
 Rotation 
 pressure 
 
 Data input 
 
 Frequency 
 
 O^ ow 
 
 Rotation 
 flow 
 
 Control 
 
 and data 
 
 input 
 
 Digital data 
 
 PC 
 
 Discrete 
 output card 
 
 On -off 
 
 bit 
 command 
 
 V off, 24 V on 
 
 MAir supply 
 V off, E 
 
 Flow 
 transducer 
 
 Volts (1-5 V) = flow 
 Frequency- 
 to-analog 
 converter card 
 
 OVoff, 
 24 Von 
 (increase 
 pressure) 
 
 24 Von 
 
 ( decrease 
 
 pressure) 
 
 ,nl 
 
 F 
 
 Supply air 
 
 PNEUMATIC DRILL SYSTEM 
 FIGURE 15.— Drill rod rotation control system. 
 
 valve 
 
 r 
 
 5> 
 
 1 
 
 4 t 
 
 u 
 
 Pneumatic 
 
 rotation 
 
 motor 
 
 Pressure- 
 regulating 
 valve 
 
 -Pilot valve 
 
 Flushing Water Control 
 
 Flushing water is controlled by a sim- 
 ple on-off command from the PC. When the 
 test operator issues the final "Start 
 Test" command through the XT keyboard 
 (see "Data Input and Startup Procedure"), 
 the PC activates a discrete output that 
 opens the water valve completely. Water 
 continues to flow to the drill until the 
 feed limit switch is closed following 
 drill retraction. Flushing water pres- 
 sure is measured and recorded, but not 
 controlled, by the PC and XT during the 
 test. A manually operated pressure- 
 reducing valve is used to adjust water 
 pressure. 
 
 Other Drill Test Commands 
 
 The drill test program software permits 
 several other operator command choices 
 from the main test menu, as shown in the 
 "Executive commands" box at the top of 
 figure 10: 
 
 results in 
 level option 
 
 Exit program (Fl) . — This 
 the display of the higher 
 menu of figure 9. 
 
 Master reset (F2). — This nulls the PC 
 holding registers that had previously 
 contained set points or test data and 
 changes the status word to that shown in 
 figure 10. Resumption of testing after a 
 "Master reset" command results in the 
 
21 
 
 same sequence as the initial startup in 
 that the drill carriage and boom move to 
 the home position before moving out to 
 the selected hole location. 
 
 Move platform home (F3). — Moving the 
 drilling rig to its home position places 
 it close to the zero position, thereby 
 shortening the initial startup process 
 for the next test session. The home pos- 
 ition is also the most convenient one for 
 drill rig maintenance; therefore, this 
 command is usually issued at the end of a 
 drill test session or when a substantial 
 amount of mechanical work (e.g. , changing 
 drills) needs to be performed on the 
 drilling rig. 
 
 Test without move (F4). — This command 
 starts the drilling process without mov- 
 ing the carriage or boom. It is used 
 most often when a successful move has 
 been completed but the maximum hole depth 
 has not been reached. For example, the 
 operator may notice a problem (e.g. , 
 stuck drill bit, leaking hose, etc.) and 
 terminate the test before the hole is 
 completed. The "Test without move" com- 
 mand enables the test to be restarted 
 (with a new test number) after the 
 
 problem has been corrected without going 
 through the time-consuming move process. 
 
 HOLE LOCATION PROGRAM 
 
 The hole location program is a very 
 convenient means for managing the loca- 
 tions and depths of all holes drilled by 
 the ADTF. It can be accessed directly by 
 the test operator to change the actual 
 position of any row or column assignment 
 in the hole location grid, or to change 
 the depth (from the program's standpoint) 
 of any hole on the existing grid. It is 
 also addressed during the startup phase 
 of the drill test program to prevent the 
 use of a hole location that has already 
 been drilled to the maximum depth of 
 12 ft. These three functions of the hole 
 location program are described below. 
 
 Selection of Hole Position 
 
 The test operator gains direct access 
 to the hole location program by choosing 
 option F3 in the menu of figure 9, which 
 results in the display of figure 16, the 
 hole location grid. The vertical hole 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ll In 
 
 le 
 
 ocation 
 
 program | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 |HO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Fl 
 
 Display 
 
 location 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 F2 
 
 Updat 
 
 e 
 
 ocation 
 
 ©-©L 
 
 ocation 
 
 
 
 
 
 Feed 1- 
 
 (D Car 
 
 
 © Boom 
 
 
 
 
 
 
 
 
 
 
 F6 
 
 Print locati 
 
 onj 
 
 
 
 
 
 
 
 
 
 
 
 Feed 2- 
 
 © Car 
 
 
 © Boom 
 
 
 
 ® Depth 
 
 
 
 
 FIO 
 
 Exit program 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 II 
 
 12 
 
 13 
 
 14 
 
 15 16 
 
 17 
 
 18 
 
 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 
 
 A 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4 
 
 
 
 B 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 D 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 E 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 6 
 
 6 
 
 
 
 F 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 G 
 
 
 
 
 
 
 
 12 
 
 3 
 
 3 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 H 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 J 
 
 
 
 
 
 2 
 
 
 
 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 6 
 
 2 
 
 6 
 
 
 
 5 
 
 
 
 5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 K 
 
 
 
 
 
 
 
 1 
 
 5 
 
 
 
 4 
 
 4 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 L 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 M 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 N 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 P 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Q 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 R 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Block 
 
 Block 2 
 
 FIGURE 16.— Data input menu for hole location program. 
 
22 
 
 positions (hole rows) are denoted by the 
 letters A through R; the horizontal posi- 
 tions are given by columns 1 through 18 
 (left-side concrete block) and 19 through 
 36 (right-side block). Operator control 
 of hole position is achieved by entering 
 information in the circled fields 1 
 through 6 in figure 16. Fields 1 and 2 
 are the row and column assignments, re- 
 spectively, of the hole to be considered. 
 Fields 3 through 6 contain the desired 
 number of counts (38 counts per inch) to 
 be issued by the position transducers en 
 route from the home position to the hole. 
 Fields 3 and 4 are the carriage and boom 
 counts for feed 1, while fields 5 and 6 
 are for feed 2. These data are then 
 placed into the appropriate PC holding 
 registers by pressing the "Update loca- 
 tion" (F2) key. A current listing of the 
 counts for each hole location can be ob- 
 tained by pressing either Fl (output to 
 video monitor) or F6 (output to printer). 
 The entire hole location grid was pre- 
 programmed in this manner to remain with- 
 in the confines of the two existing con- 
 crete blocks. Spacing between adjacent 
 rows and columns was set at 4 in, and the 
 pattern was staggered by 2 in (i.e., 
 even-numbered columns were shifted 2 in 
 downward from odd-numbered columns) to 
 provide an actual hole spacing of about 
 4.5 in. Under normal circumstances, the 
 test operator would have no reason to 
 change the preprogrammed hole positions. 
 However, an important exception occurs 
 when considering the use of drilling 
 media other than the concrete blocks. 
 For example, a granite test block was in- 
 serted into the wall between the concrete 
 blocks, and previously unused hole loca- 
 tions around the perimeter of the con- 
 crete blocks were utilized to establish a 
 hole pattern on the granite block. The 
 only constraints on hole position are the 
 physical travel limits of the carriage 
 and boom. 
 
 Validation of Input Data 
 
 At the end of each drill test, the 
 drill test program automatically enters 
 the hole depth (in feet) into the 
 hole location program. If the operator 
 
 subsequently specifies a hole location 
 that has already been drilled to the max- 
 imum depth (e.g. , location G-5 in figure 
 16) or asks for a depth that would exceed 
 the maximum at that location (e.g., a 7- 
 ft hole at location J-21), the drill test 
 program issues an error message. Testing 
 cannot proceed until the error is cor- 
 rected by specifying either another hole 
 location or a shallower hole depth. 
 
 Selection of Hole Depth 
 
 During the initial programming of the 
 hole location grid, the depth of each 
 hole was set to zero via field 7 of fig- 
 ure 16. Subsequent drill tests resulted 
 in the assignment of actual hole depths 
 to various locations. In some cases, 
 however, it is desirable for the operator 
 to arbitrarily assign hole depths through 
 the hole location program. For example, 
 a very large drill hole at a particular 
 location may interfere with adjacent 
 holes if the holes are not perfectly 
 straight; damage to the drill rod or 
 drill could result if the holes intersect 
 within the block. Therefore, even though 
 the actual depths of the adjacent holes 
 are zero, the operator may wish to enter 
 a depth of 12 ft into the hole location 
 program (field 7 of figure 16). This 
 will cause an error message to appear if 
 the operator tries to select these holes 
 for drill tests. The hole depth selec- 
 tion feature also allows easy re- 
 initialization after the concrete blocks 
 are replaced. 
 
 DATA ANALYSIS PROGRAM 
 
 The drill test software possesses very 
 powerful analytical capabilities. Any 
 drilling parameter stored to disk can be 
 studied and compared graphically to any 
 other variable. The data analysis pro- 
 gram can be called in from the overall 
 software menu (fig. 9) or the main drill 
 test menu (fig. 10) for simultaneous 
 analysis of any two tests. The data re- 
 corded to disk can also be converted 
 easily to commercially available spread- 
 sheet files (Lotus 1-2-3) for subsequent 
 analysis using the spreadsheet software. 
 
23 
 
 Direct Data Analysis and Graphics 
 
 Test Selection 
 
 Recall that all test data are stored on 
 
 floppy disks in files namea "TEST .- 
 
 DAT," with the blanks corresponding to 
 the four-digit test number assigned by 
 the XT. When data analysis is desired, 
 the test operator first makes sure the 
 correct test numbers are available on the 
 floppy disk by selecting option F4, "Di- 
 rectory of tests on A:" from the overall 
 software menu shown in figure 9. The 
 operator then chooses the data analysis 
 program (F2), which results in the dis- 
 play of the menu in figure 17. The test 
 or tests to be analyzed are selected by 
 entering the four-digit test number(s) 
 in fields 1 and 2 of figure 17 and press- 
 ing the F9 "Retrieve tests (s)" key. Note 
 in figure 17 that tests 0178 and 0293 
 have been selected. Test 0178 is that of 
 a small, muffled pneumatic percussion 
 drill; test 0293 is that of a small, all- 
 rotary pneumatic drill. These two tests 
 will be used below to illustrate the 
 basic graphics capability of the data 
 analysis program. Further comparisons 
 between the two drills are contained in 
 the section of this report entitled "Ini- 
 tial Test Results." 
 
 Raw Data Retrieval 
 
 The "List test" and "Print test" op- 
 tions in figure 17 (function keys F7 and 
 F8) are used to retrieve all the data re- 
 corded during a given test. "List test" 
 displays the data only on the XT video 
 monitor; "Print test" also provides a 
 hard copy of this information. Figure 18 
 shows the data recorded for the first 45 
 s of test 0293. Descriptive information 
 is given at the beginning of the test 
 file, and the entry of new test parameter 
 values is documented at 15.7 and 26.3 s. 
 The top row of figure 18 shows all the 
 drilling parameters recorded during the 
 test and the units in which they are 
 given. Sound power information is given 
 at 18.1 and 36.2 s; the first 21 values 
 in the string correspond to the twenty- 
 one 1/3-octave bands comprising the 100- 
 to 10,000-Hz frequency range, and the 
 final value is the overall (unweighted) 
 sound power level. Note that in this 
 particular test, the values for hammer 
 pressure and drill blow frequency appear 
 as dummy values of 1.0 and 0.0, respec- 
 tively, because of the all-rotary operat- 
 ing mode of the tested drill. 
 
 The ability to scan the entire set of 
 test data in this manner helps the test 
 operator in several ways: (1) Graphs 
 
 
 
 menu 
 
 
 Fl 
 
 Analysis 
 
 Plot feed thrust 
 
 Plot hammer pressure 
 
 F2 
 
 F3 
 
 Plot feed rate 
 
 F4 
 
 Plot sound power 
 
 F5 
 
 Plot spectrum 
 
 F6 
 
 Plot spectrum waterfall 
 
 F7 
 
 List test 
 
 F8 
 
 Print test 
 
 F9 
 
 ©Retrieve test: 0178 
 ©Retrieve test: 0293 
 
 FIO 
 
 Exit 
 
 ©X minimum ®X maximum 
 ©Y minimum ®Y maximum 
 
 FIGURE 17. — Data input menu for analysis program. 
 
24 
 
 Test 0293 
 
 Drill tested' GOPHER Pneumatic or hydraulic: P Feed" I Hole size : \V\e" 
 
 Drill steel- 1" HEX Bit type- POS R Location: I -02 
 
 Comments : retest GOPHER at optimum settings 
 
 Time, 
 s 
 
 Rotation 
 flow, 
 g/cf' 
 
 Distance 
 
 drilled, 
 
 in 
 
 Hammer 
 pressure, 
 psi 
 
 Feed 
 thrust, 
 
 Ibf ' 
 
 Feed 
 rate, 
 in/s 
 
 Drill 
 frequency, 
 
 Hammer 
 
 Rotation 
 pressure, 
 psi 
 
 Flushing 
 water, 
 psi 
 
 
 Values- Hammer pressure = 1 Rotation flow = 100 
 Feed thrust = 200 Distance drilled = 48 
 
 0.1 
 
 102.1 
 
 0.1 
 
 1 
 
 201.6 
 
 
 
 
 
 
 
 90.4 
 
 52.5 
 
 4.1 
 
 102.3 
 
 4.5 
 
 1 
 
 204.1 
 
 I.I 
 
 
 
 
 
 82.1 
 
 60 
 
 8.1 
 
 101.8 
 
 6 
 
 1 
 
 199 
 
 0.4 
 
 
 
 
 
 83.6 
 
 61 
 
 12.1 
 
 85.4 
 
 6.3 
 
 1 
 
 209.3 
 
 0.1 
 
 
 
 
 
 76.7 
 
 60 
 
 15.7 
 
 New Hammer pressure = 1 Rotation flow = 120 
 values : Feed thrust = 200 Distance drilled = 48 
 
 16.1 
 
 86.2 
 
 6.5 
 
 1 
 
 188.6 
 
 0.1 
 
 
 
 
 
 78.7 
 
 60.1 
 
 18.1 
 
 Sound power, 81.2, 83.4, 85.4, 87.7, 92.5, 92.1, 97, 93.5, 91.6, 96.8, 
 d B= 93.8, 97.5, 94.9, 88.9, 973, 92.3, 91.2, 88.9, 85.9, 
 86.2, 105.4 
 
 20.2 
 
 116.9 
 
 6.7 
 
 1 
 
 201.6 
 
 0.1 
 
 
 
 
 
 100.2 
 
 60.4 
 
 24.2 
 
 117.2 
 
 7 
 
 1 
 
 201.6 
 
 0.1 
 
 
 
 
 
 97.8 
 
 60.7 
 
 26.3 
 
 New Hammer pressure = 1 Rotation flow = 120 
 values^ Feed thrust = 500 Distance drilled = 48 
 
 28.2 
 
 112.6 
 
 8.1 
 
 1 
 
 739 
 
 0.3 
 
 
 
 
 
 97.3 
 
 61 
 
 32.3 
 
 113.9 
 
 9.7 
 
 1 
 
 522 
 
 0.4 
 
 
 
 
 
 101.7 
 
 60.7 
 
 36.2 
 
 Sound power, 83, 85.6, 87, 89.7, 95, 95.5, 99.3, 95.7, 93.5, 
 dB= 100.6, 97.5, 98.6, 99.2, 93.2, 96.1, 94.7, 93.8, 
 92.4, 90,90.2, 90.9, 1078 
 
 36.5 
 
 112.3 
 
 11.3 
 
 1 
 
 532.3 
 
 0.4 
 
 
 
 
 
 99.7 
 
 60.6 
 
 40.6 
 
 II 2.1 
 
 12.5 
 
 0.5 
 
 558.1 
 
 0.3 
 
 
 
 
 
 97.8 
 
 60.9 
 
 44.7 
 
 114.4 
 
 13.8 
 
 1 
 
 480.6 
 
 0.3 
 
 
 
 
 
 99.2 
 
 60.6 
 
 Note : the notation g/cf for rotation flow reflects 
 
 fact that flow is measured in gpm for hydraulic 
 drills and cfm for pneumatic drills. 
 
 FIGURE 18— Printout of drill test data. 
 
25 
 
 generated by the software are more easily 
 interpreted with the availability of hard 
 numbers, especially when input parameters 
 are changed during a test, (2) particu- 
 larly interesting portions of a test can 
 be isolated for more detailed analysis, 
 and (3) data anomalies that sometimes oc- 
 cur at the start of a test are easier to 
 identify. 
 
 Basic System Graphics 
 
 The function keys Fl through F6 in fig- 
 ure 17 are used to display graphs on the 
 XT video monitor; hard copies are ob- 
 tained easily by pressing the "Print 
 screen" key of the XT keyboard when the 
 graph is displayed. Function keys Fl 
 through F4 provide graphs that utilize 
 the indicated test parameter as the de- 
 pendent (Y-axis) variable and elapsed 
 time as the independent (X-axis) 
 
 variable. Function key F5 plots the 1/3- 
 octave band sound power levels versus 
 frequency, and F6 provides a simulated 
 three-dimensional graph with frequency as 
 the X-axis, 1/3-octave band sound power 
 level as the Y-axis, and time as the Z- 
 axis. Figures 19 and 20 are examples of 
 these graphs for tests 0178 and 0293. 
 
 Fields 3 through 6 in figure 17 are 
 used by the test operator to define the 
 range of values to be displayed on the X- 
 and Y-axes of each graph. These values 
 are entered before pressing the function 
 key for the desired graph. If these 
 fields are left blank, the range is de- 
 termined by the actual minimum and maxi- 
 mum values contained in the data. In 
 figures 19 and 20, ranges were selected 
 such that all test data would be dis- 
 played on easily readable axes. For 
 example, the total elapsed time in each 
 test was slightly greater than 150 s; 
 
 (A 
 Q. 
 
 Ill 
 
 QC 
 
 Z> 
 
 <n 
 en 
 
 UJ 
 
 rr 
 o. 
 
 a: 
 
 < 
 
 x 
 
 UJ 
 
 a 
 
 UJ 
 UJ 
 
 75 
 
 
 1 1 
 
 ^-Test 0178 
 
 50 
 
 I 
 
 - 
 
 25 
 
 ■— 1 
 
 r-Test 0293 
 
 800 
 
 200 
 
 200 
 
 CO 
 
 "o I20h 
 
 UJ 
 
 r?. 115 
 
 8 M0 
 
 o 
 
 °- 105 
 
 a 
 
 z 
 
 o ioo 
 
 CO 
 
 95 
 
 
 Test 0178 
 
 Test 0293 
 
 50 100 150 200 50 100 
 
 TIME, s 
 FIGURE 19.— Graphs of hammer pressure, feed thrust, feed rate, and sound power versus elapsed time. 
 
 1 50 
 
26 
 
 
 110 
 
 
 105 
 
 
 100 
 
 
 95 
 
 m 
 
 90 
 
 _i 
 
 UI 
 
 85 
 
 > 
 
 
 U 
 
 
 _l 
 
 80 
 
 E 
 
 
 UJ 
 
 110 
 
 o 
 
 
 0. 
 
 
 
 105 
 
 Q 
 
 
 Z 
 
 
 3 
 O 
 
 100 
 
 </) 
 
 
 
 95 
 
 
 90 
 
 
 85 
 
 
 80 
 
 1 
 
 
 1 ' 
 
 . 
 
 
 r Test 0178 
 
 "I 1 T— ' 1 1 1 1— 
 
 \s 
 \ \ 
 
 f\ "N. 
 
 /vs J> — : 
 
 / \ /A rTest 0293 
 /^ ^ V/ \ 1 
 
 ! 
 
 
 ■ i 
 
 I 6 II 16 21 
 
 FREQUENCY, l/3"octave band number 
 
 FIGURE 20.— Sound power spectrum and spectrum waterfall 
 graphs. 
 
 therefore, the "Xmax" (field 4) value in 
 the time-based graphs was set at 200 s so 
 that values of 50, 100, and 150 s would 
 occur at the three computer-generated 
 subdivisions. Maximum and minimum values 
 for all the other parameters were chosen 
 in the same manner. 
 
 Hammer pressure (fig* 19). — Ha mme r 
 pressure for test 0178 (pneumatic percus- 
 sion drill) was set at 90 psi; the ADTF 
 achieved this pressure shortly after 
 startup and maintained it very con- 
 sistently throughout the test. Hammer 
 pressure for test 0273 was set at a nom- 
 inal value of 1 psi (rotary drill). 
 
 Feed thrust (fig. 19). — Feed thrust in 
 test 0178 was set at 240 lbf and remained 
 there throughout the test. Feed thrust 
 in test 0293 was initially set at 
 200 lbf; after the hole was collared, 
 thrust was increased to 500 lbf. Except 
 for the brief spike that occurred as the 
 ADTF adjusted to the higher set point, 
 feed thrusts remained fairly close to the 
 set point values. 
 
 Feed rate (fig. 19). — The abnormally 
 high feed rate at the start of each test 
 corresponds to the forward movement of 
 the drill before the bit contacts the 
 concrete. After collaring, both drills 
 
 achieved a fairly steady feed rate of 0.3 
 to 0.5 in/s, although the percussion 
 drill was somewhat faster. In test 0293, 
 an abnormally low feed rate occurred dur- 
 ing collaring because of the low feed 
 thrust; this rose markedly when the feed 
 thrust was increased. 
 
 Sound power (fig. 19). — Sound power of 
 the rotary drill (test 0293) was very 
 consistent at 105 to 107 dB through the 
 test. Sound power of the percussion 
 drill (test 0178) was around 115 dB at 
 the start of the test, but decreased as 
 the drill rod entered the hole. This ef- 
 fect did not occur in test 0293 because 
 the drill rod is not a major contributor 
 to rotary drill noise. 
 
 Spectrum (fig. 20). — The 1/3-octave 
 band sound power levels in these two 
 tests were very similar at low frequen- 
 cies. The major difference between the 
 two spectra occurred at higher frequen- 
 cies, where the drill rod noise of the 
 percussion drill was more prominent. 
 
 Note in figure 20 that frequency data 
 are reported in "band number" rather than 
 Hertz because this is the way the sound 
 power calculator reports frequency data 
 to the XT. In this case, band 1 corre- 
 sponds to 100 Hz and band 21 corresponds 
 to 10,000 Hz. However, since Hertz is 
 the universally accepted unit of fre- 
 quency measurement, the use of band num- 
 ber in graphs represents a major defi- 
 ciency of the basic system graphics. Two 
 other limitations of the basic system 
 graphics for sound power spectra are that 
 (1) only the final sample recorded during 
 the test is graphed when the F5 key in 
 figure 17 is pressed and (2) the overall 
 sound power level cannot be plotted on 
 the same graph as the 1/3-octave band 
 data. As discussed in the next section, 
 all three of these problems can be re- 
 solved by using electronic spreadsheets 
 to look at frequency data. 
 
 Spectrum waterfall (fig. 20). — Th i s 
 shows how the noise frequency spectrum 
 varies during a test. It can provide 
 useful qualitative information with re- 
 gard to frequency shifts during the 
 course of the test, but it is of little 
 value for quantitative comparisons. Ow- 
 ing to the complexity of the spectrum 
 
27 
 
 waterfall graph, it can be displayed for 
 only one test at a time. 
 
 Expanded Data Analysis Through 
 Spreadsheets 
 
 Given the limitations of the basic sys- 
 tem graphics, a method for obtaining a 
 more complete data analysis was desired. 
 The most effective approach was to con- 
 vert the test data files to electronic 
 spreadsheet files. Lotus 1-2-3 was 
 chosen as the spreadsheet program because 
 of its ready availability and compatibil- 
 ity with the IBM-XT. To avoid the manual 
 entry of test data into the spreadsheet 
 files, special software was written to 
 convert the individual parameters of the 
 
 "TEST .DAT" files into a format that 
 
 could be read by the lotus program's 
 
 "File Import" function. For convenience, 
 the Lotus Formatter program and the stan- 
 dard Lotus 1-2-3 software are contained 
 on the hard disk. 
 
 File Conversion Procedure 
 
 The step-by-step procedure for convert- 
 ing the "TEST .DAT" files to Lotus 1- 
 
 2-3 files is described below: 
 
 1. The test operator loads the Lotus 
 Spreadsheet Formatter program into the 
 XT, which results in the display of the 
 menu shown in figure 21. 
 
 2. The four-digit test number of the 
 test to be formatted is entered into 
 field 1 of figure 21. 
 
 3. The parameters to be formatted 
 are selected by placing any nonzero 
 
 
 
 
 
 
 
 opreaasheei rurmauer 
 
 
 F 1 Exit 
 
 
 
 F5 Delete specific ??x. PRN files 
 
 F9 Extract drill test data FIO Extract noise test data 
 
 
 
 Test (T> » 
 
 © HPx. PRN 
 © HFx. PRN 
 
 Hammer pressure Drill test only 
 Hammer flow 
 
 
 
 
 © RPx. PRN 
 
 Rotation pressure 
 
 
 © RFx. PRN 
 
 Rotation flow 
 
 
 © FTx. PRN 
 
 Feed thrust 
 
 
 ® FRx. PRN 
 
 Feed rate 
 
 
 © DFx. PRN 
 
 Drill frequency 
 
 
 ® DDx. PRN 
 
 Distance drilled 
 
 
 © FWx. PRN 
 
 Flushing water 
 
 
 © SPx. PRN 
 
 Sound power 
 
 
 @ ASx. PRN 
 
 Average spectrum 
 
 
 @ PSx. PRN 
 
 2131 Average spectrum 
 
 ® Target director 
 
 y : 
 
 © x = 1 
 
 © Resample time : 1 s © Start time 5 s ® Stop time : 60 s 
 
 FIGURE 21. — Data input menu for Spreadsheet Formatter program. 
 
28 
 
 character in fields 2 through 13. The 
 general names of the files to be created 
 by the Lotus Formatter (see item 5 below 
 for specific file names) are shown im- 
 mediately to the right of fields 2 
 through 13, and the parameter names are 
 displayed on the right of the file 
 names. 
 
 4. The disk drive to which the format- 
 ted files will be written is entered into 
 field 14. The hard disk (c): is the 
 default drive. 
 
 5. The specific names of the files to 
 be created by the Lotus Formatter are 
 chosen by entering any of the numbers 1 
 through 9 into field 15. For example, if 
 nonzero characters were entered in fields 
 2 and 9 and the default value of 1 were 
 left in field 15, the two files created 
 would have the names "HP1.PRN" and 
 "DDI.PRN." Up to nine Lotus-formatted 
 files for each parameter can thus be con- 
 tained on any one output target (floppy 
 or hard disk), and almost an unlimited 
 number of such files can be maintained 
 by renaming the files after they are 
 formatted. 
 
 6. The amount of drill test data to 
 be formatted is chosen by entering the 
 appropriate values in fields 16, 17, and 
 18. Since the Lotus Formatter program 
 uses the "Elapsed Time" parameter as a 
 key, field 17 (Start time) and field 18 
 (Stop time) determine the portion of the 
 test to be formatted. The default values 
 of 0.0 and 60.0 s are shown in figure 21. 
 Field 16 (Resample time), specifies the 
 interval at which the Lotus Formatter 
 
 program will recheck the "TEST .DAT" 
 
 file for new data. When the default val- 
 ue of 1.0 s is shown in figure 21, the 
 program interpolates between the actual 
 values recorded at 4- or 18-s intervals. 
 
 7. When all selections in fields 1 
 through 17 have been made, the F9 key is 
 pressed to perform the file conversions. 
 Confirmation messages and/or error mes- 
 sages appear at this time, including an 
 option to overwrite any "xxx. PRN" files 
 that are already located on the target 
 directory. Pressing F5 rather than F9 
 deletes from the target directory any 
 files whose names are the same as those 
 of the "marked" files. 
 
 8. The operator exits the Lotus For- 
 matter program, enters Lotus 1-2-3, and 
 calls in a special worksheet file that 
 contains A-weighting correction factors, 
 convenient column headings, and appropri- 
 ate axis labels for later graphs. This 
 serves as a template worksheet to which 
 the formatted drill test files will be 
 imported. 
 
 9. The cursor is moved to the area of 
 the worksheet in which the test data are 
 to appear, and the "File Import" proce- 
 dure of Lotus 1-2-3 is used to call in 
 the formatted files. This procedure is 
 repeated for each "xxx. PRN" file created 
 in steps 1 through 7 above. 
 
 10. The standard Lotus 1-2-3 file man- 
 ipulation and graphics options are uti- 
 lized to perform the desired analyses. 
 Examples of the use of Lotus graphics are 
 given in the section of this report 
 entitled "Initial Test Results." 
 
 Note that fields 2 through 11 corres- 
 pond to the drilling parameters listed in 
 figure 18. Fields 12 and 13 are special 
 parameters that are created by the Lotus 
 Formatter software prior to conversion. 
 The "Average spectrum" (field 12) con- 
 sists of the logarithmic average of the 
 sound power levels in each of the twenty- 
 one 1/3-octave bands, with the number of 
 samples determined by the specified start 
 and stop times. For example, the default 
 values of 0. and 60. s would result in 
 the averaging of three sound power values 
 per frequency band (data at 18, 36, and 
 54 s). Field 13 is analagous to field 12 
 except that the Lotus Formatter looks for 
 sound pressure data recorded from the 
 Bruel & Kjaer model 2131 digital fre- 
 quency analyzer. 
 
 Advantages of Spreadsheet Analysis 
 
 Multivariable Comparisons 
 
 The basic system graphics package can 
 only plot drilling parameters versus 
 time. With spreadsheet analysis, any two 
 parameters in a given test can be com- 
 pared against each other. The most fre- 
 quent use of this capability would be the 
 comparison of sound power and hole depth. 
 
29 
 
 Also, if one or more drilling parameters 
 are changed during the test, the effect 
 of these changes on all other parameters 
 can be displayed graphically. 
 
 Multitest Comparisons 
 
 The Lotus 1-2-3 graphics package can 
 display the results of up to six tests on 
 the same graph, versus only two for the 
 basic system graphics package. Para- 
 metric studies (where only one variable 
 is changed from test to test, to observe 
 its effect on other variables) are there- 
 fore much easier to perform. This cap- 
 ability also facilitates comparisons 
 among several different types and models 
 of drills. 
 
 Frequency Analysis 
 
 As mentioned above, the limited fre- 
 quency analysis capability of the basic 
 system graphics package is one of its 
 greatest deficiencies. Spreadsheet anal- 
 ysis overcomes these deficiencies in the 
 following ways: 
 
 1. The average frequency spectrum from 
 any portion of the test can be obtained 
 by judicious selection of the start and 
 stop times in the Lotus Formatter program 
 (fields 17 and 18 in figure 21). In this 
 manner a two-dimensional "spectrum water- 
 fall" can be created to observe how the 
 spectra change during the course of a 
 test. 
 
 2. A-weighting of the 1/3-octave band 
 noise levels can be performed quickly and 
 easily. An overall A-weighted level for 
 each spectrum can then be calculated and 
 displayed on the same graph as the 1/3- 
 octave band data. 
 
 3. Frequency rather than band number 
 can be displayed as the X-axis of all 
 graphs. 
 
 Analysis of Other Noise Tests 
 
 Since the Lotus Formatter can operate 
 on any data file created by the sound 
 measuring instrumentation, it can be used 
 to analyze noise information from any 
 test conducted in the reverberation cham- 
 ber. A separate noise test program al- 
 lows this instrumentation to be activated 
 through the XT, and causes it to write 
 the noise data to disk with a file name 
 of "NOIS .DAT". The Lotus Formatter 
 program can then be used to convert the 
 data to a "xxx.PRN" file. The same 10- 
 step procedure described above is used 
 instead of the F9 "Extract drill test 
 data" command. As noted in figure 21, 
 drilling parameters cannot be converted 
 using the F10 command. One of the most 
 common uses of the noise test program is 
 to read the room correction factors from 
 the Bruel & Kjaer 7507 sound power cal- 
 culator. Knowledge of these room correc- 
 tion factors allows the sound pressure 
 levels to be calculated from the sound 
 power levels using the Lotus software. 
 
 INITIAL TEST RESULTS 
 
 To further demonstrate the abilities of 
 the automated drill test fixture, some 
 observations of the initial test data are 
 included. Three types of drills were 
 tested to help assure that the test fix- 
 ture was capable of performing as speci- 
 fied. A pneumatic percussion drill, a 
 hydraulic percussion drill, and a pneu- 
 matic rotary drill were all run in the 
 concrete test medium to compare perfor- 
 mance against the manufacturers ' pub- 
 lished data and to measure their sound 
 power levels in an operating situation. 
 All three drills are of the small 
 
 "hand-held" class for which noise control 
 technology has been difficult to 
 implement. 
 
 The general test scheme involves find- 
 ing the set of operating parameters that 
 results in the optimum penetration rate 
 for the drill being tested and measuring 
 the sound power level under these condi- 
 tions. However, drills designed to oper- 
 ate in soft rock perform better in the 
 concrete test medium than those designed 
 to drill hard rock. Therefore, it is 
 possible that the penetration rates pre- 
 sented here could be different if the 
 
30 
 
 drills were tested in a hard drilling 
 medium. 
 
 Several points should be noted about 
 the test data. Most importantly, the 
 number of tests to date is too small to 
 generate statistically valid results con- 
 cerning the behavior of the drills under 
 differing operating conditions. Second, 
 the primary purpose of these tests has 
 simply been to verify the capabilities of 
 the ADTF in terms of process control, 
 data collection, and test analysis; how- 
 ever, operation of the test fixture has 
 still yielded some interesting informa- 
 tion. The confirmation of the contribu- 
 tion of the drill steel to the overall 
 noise level in percussion drills is one 
 factor that can be noted from the avail- 
 able data. 
 
 PNEUMATIC VERSUS HYDRAULIC PERCUSSION 
 DRILLS 
 
 The drill used for the tests of pneu- 
 matic percussion drill was a Technologi- 
 cal Enterprises QHR drill, a quieted 
 
 pneumatic drill developed under contract 
 with the Bureau of Mines (9-10). Its 
 valveless design, independent rotation, 
 and integral muffler make the QHR drill 
 one of the quietest in its class. A Tarn- 
 rock HH-50 was chosen to represent hy- 
 draulically powered percussion drills. 
 This drill also has independent rotation 
 and is capable of accommodating either 
 water or air flushing, as is the QHR. 
 The sound power spectra of these two 
 drills are shown together in figure 22. 
 
 The QHR and the HH-50 are in approxi- 
 mately the same weight and power-output 
 class and give a fairly good comparison 
 between the two different power sources. 
 During the tests chosen for comparison, 
 the QHR drilled at a rate of 1.95 ft/min 
 under an average thrust of 245 lbf and 
 the HH-50 drilled at a rate of 
 2.20 ft/min under an average thrust of 
 277 lbf. Although they are not typically 
 used for concrete drilling, button bits 
 were used to maintain bit consistency 
 during testing. 
 
 106 
 
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 £ 98 
 
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 KEY 
 
 ■ Pneumatic percussion drill 
 a Hydraulic percussion drill - 
 
 25 
 
 250 
 
 500 1,000 2,000 4,000 8,000 16,000 
 FREQUENCY, Hz 
 
 FIGURE 22. — Average frequency spectra: pneumatic and hydraulic percussion drills. 
 
31 
 
 It can be noted in figure 22 that the 
 drills differ significantly in sound 
 power output between 160 and 1,250 Hz. 
 This area is dominated by the noise pro- 
 duced by the exhaust of the pneumatic 
 drill. The difference would be even 
 larger if the pneumatic drill were not 
 muffled. At 1,000 Hz and above, the two 
 drills produce approximately the same 
 power spectrum. This is to be expected 
 as the noise in this frequency range is 
 characteristic of the drill body and 
 drill steel. 
 
 The sound power output at 1,250 to 
 8,000 Hz is largely a product of the ex- 
 posed drill steel. In particular, the 
 spectra from 1,250 to 4,000 Hz are almost 
 identical. This is not surprising be- 
 cause the two drills operate at about the 
 same frequency and the length of the 
 steel in both tests was the same. This 
 noise is not produced solely by the drill 
 itself, and in operating situations it is 
 inseparable from the drill body noise. 
 
 In the future, when tests for actual 
 drill sound power output are performed, 
 the drill steel noise will be eliminated 
 by removing the steel from the test. 
 This will be accomplished by using a 
 "dead block." The dead block is simply a 
 device that can absorb and dissipate the 
 energy produced by the drill, usually in 
 the form of heat. The drill will be 
 coupled to the dead block by a very short 
 section of steel that will be acoustical- 
 ly isolated from the test environment. 
 For the present, however, the dead block 
 is not being used so the effect of the 
 drill steel can be observed as it occurs 
 in the actual operation of the drill. 
 
 Research by Hawkes (12) shows that 
 noise produced by the drill steel is 
 caused primarily by bending waves in the 
 steel. These bending waves occur at many 
 frequencies above a critical frequency 
 and are calculated by the formula 
 
 where fe = bending wave frequency, Hz, 
 
 n - 
 
 D = 
 L = 
 
 and C, = 
 
 mode number (1 for first 
 critical frequency), 
 
 drill steel diameter, in, 
 
 drill steel length, in, 
 
 speed of sound in drill 
 steel, 2 x 10 5 in/s. 
 
 f R = n 2 
 
 DC, 
 
 [l-1.2(nD/L)2], 
 
 TIT 
 
 These bending wave frequencies are 
 spaced sufficiently close together to 
 produce noise in all 1/3-octave bands 
 above the initial frequency. 
 
 Note in the above equation that the 
 bending wave frequencies are directly re- 
 lated to the length of the drill steel; 
 the longer the steel, the lower the first 
 critical frequency. The drill steel 
 used in the tests of the percussion 
 drills was 10 ft in length, resulting in 
 a first critical frequency of approxi- 
 mately 5 Hz, well below the 1/3-octave 
 band centered at 31.5 Hz. The contribu- 
 tion to the overall noise level occurs in 
 all bands measured but is considerably 
 larger at frequencies above 2,000 Hz 
 (fig. 23). This is of particular import- 
 ance up to 4,000 Hz because of the poten- 
 tial effects on hearing loss. The noise 
 levels drop over the course of a test due 
 to the entrance of the drill steel into 
 the hole. The section of steel that has 
 penetrated is shielded from the test en- 
 vironment, and the overall contributution 
 of the steel is thus reduced. 
 
 This type of information is particular- 
 ly useful when designing noise controls 
 for drills or when attempting to develop 
 noise-controlled operating procedures. 
 The time effects would be difficult to 
 observe with traditional data collection 
 methods but are easily noted by the reg- 
 ularly spaced intervals of data provided 
 by the test fixture's data collection 
 system. 
 
32 
 
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 Pneumatic percussion dri 
 
 125 250 500 1,000 2,000 4,000 8,000 16,000 
 
 250 500 1,000 2,000 4,000 8,000 16,000 
 FREQUENCY, Hz 
 
 FIGURE 23. — Frequency spectra for percussion drills, begin- 
 ning versus end of hole. 
 
 ROTARY VERSUS PERCUSSION DRILLS 
 
 A pneumatic rotary drill, the ALMINC0 
 Gopher, was also tested on the drill test 
 fixture. The intended uses of the Gopher 
 are roughly the same as for the two per- 
 cussion drills; however, rotary drills 
 operate at higher thrust levels than per- 
 cussion drills. This fact, combined with 
 the different control demands of a rotary 
 drill, allowed the test fixture to be 
 operated over a greater range of thrust 
 values than when testing percussion 
 drills alone. The Gopher drilled at a 
 rate of 1.57 ft/min under an average 
 thrust of 521 lbf during the test se- 
 lected for comparison. The data re- 
 trieved from the tests of the rotary 
 drill provide some interesting contrasts 
 to both of the percussion drills. 
 
 The sound power spectrum of the rotary 
 drill is similar to that of the pneumatic 
 percussion drill from the standpoint of 
 the pneumatic exhaust, but it differs 
 from those of the percussion drills in 
 
 the relatively minor contribution of 
 drill steel noise. These observations 
 are evident in figure 24. The portion of 
 the spectrum from 200 Hz to 1 kHz is 
 greater in level for the two pneumatical- 
 ly powered drills than for the hydrau- 
 lically powered drill. The greater con- 
 tribution by the drill steel of the per- 
 cussion drills can be seen at 2 kHz and 
 above. The absence of drill steel noise 
 is also shown in the sound power levels 
 taken at intervals during the test. 
 The overall levels for the rotary drill 
 differ by less than 1 dB from beginning 
 to end, and the average spectra are ap- 
 proximately the same (fig. 25), indicat- 
 ing that noise radiated from the rotary 
 steel is not a major contributor to the 
 overall noise level. 
 
 Another good example of the types of 
 phenomena that can be observed is illus- 
 trated by the shape of the average test 
 spectra (fig. 24). A potential problem 
 with the rotary drill is revealed near 
 the center of the graph. It can be noted 
 from the graph that the portion of the 
 spectrum from which a majority of the 
 noise is produced is in a relatively 
 small range that differs from the predom- 
 inant noise of the percussion drills. 
 The span of frequencies in the 1/3-octave 
 bands centered from 800 to 1,600 Hz con- 
 tains over half of the total sound 
 energy. These frequencies overlap the 
 range of human speech. Hearing loss at 
 these frequencies greatly impacts func- 
 tional hearing ability. Based on the ob- 
 servation of overall levels alone, or 
 even individual narrow band spectra pro- 
 duced from recordings of field test, one 
 may conclude that the rotary drill is 
 less of a noise problem than the percus- 
 sion drills; however, by examining the 
 operation of the drill more closely, it 
 can be seen that a more thorough investi- 
 gation of the sources is necessary. 
 
 The positive side to this particular 
 observation is that the peak noise pro- 
 duced by the rotary drill has more poten- 
 tial solutions than the noise produced by 
 the percussion drills. The frequency 
 range of the noise, along with informa- 
 tion about the operating principles of 
 the drill, suggests that the noise arises 
 from the gear motor that drives the 
 
33 
 
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 82- 
 
 78 » 
 
 KEY 
 
 ■ Pneumatic percussion drill 
 a Hydraulic percussion drill 
 • Pneumatic rotary drill 
 
 125 250 500 1,000 2,000 4,000 8,000 16,000 
 
 FREQUENCY, Hz 
 
 FIGURE 24.— Average frequency spectra: pneumatic and hydraulic percussion drills, pneumatic rotary drill. 
 
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 125 250 500 1,000 2,000 4,000 8,000 16,000 
 
 FREQUENCY, Hz 
 
 FIGURE 25.— Frequency spectra for pneumatic rotary drill: beginning versus end. 
 
34 
 
 drill. This type of noise can sometimes 
 be attenuated by redesigning the rotors 
 and reduction gears to shift the fre- 
 quency into a more tolerable range. 
 
 It should be pointed out again that 
 these are merely observations of selected 
 
 test data and are in no way statistically 
 representative of the way the drills 
 behave, especially in terms of penetra- 
 tion rate. 
 
 DISCUSSION 
 
 The automated drill test fixture is a 
 very powerful tool for studying the noise 
 characteristics and operational perfor- 
 mance of percussion and rotary drills. 
 The unique feature of the ADTF is that it 
 is housed within a large reverberation 
 chamber to allow the easy calculation of 
 drill sound power levels. Sound power 
 data are not usually provided by drill 
 manufacturers, so the ADTF can supply 
 drill users with information that has 
 previously been unavailable. If noise is 
 a consideration when selecting a drilling 
 system, this information can be very 
 valuable. 
 
 The ability to achieve control over all 
 important drill operating parameters is a 
 key advantage of the ADTF. Test condi- 
 tions can thus be reproduced exactly or 
 changed to study the effect of one or 
 more parameters on the overall perfor- 
 mance of the drill. Diagnostic work of 
 
 this type can provide useful information 
 on drill penetration rate as well as 
 noise. The ability to change drilling 
 media is very important when examining 
 drill penetration rate. Each drill must 
 be tested in the medium for which it was 
 designed (soft, medium, or hard rock) in 
 order to make valid comparisons of drill 
 penetration. 
 
 Initial tests conducted with the ADTF 
 confirmed that it is capable of achiev- 
 ing the desired process control and data 
 recording functions. The data analysis 
 software greatly facilitated the inter- 
 pretation of these initial tests. Gen- 
 eral observations were made with respect 
 to the noise produced by pneumatic per- 
 cussion, hydraulic percussion, and pneu- 
 matic rotary drills. A much more exten- 
 sive testing program with each of these 
 drills must be conducted before defini- 
 tive comparisons can be made. 
 
 REFERENCES 
 
 1. Patterson, W. N. , G. G. Huggins, 
 and A. G. Galaitsis. Noise of Diesel- 
 Powered Underground Mining Equipment: 
 Impact, Prediction, and Control (contract 
 H0346046, Bolt Beranek and Newman, Inc. ). 
 BuMines OFR 58-75, 1975, 227 pp.; NTIS 
 PB 243 896. 
 
 2. Visnapuu, A. , and J. W. Jensen. 
 Noise Reduction of a Pneumatic Rock 
 Drill. BuMines RI 8082, 1975, 23 pp. 
 
 3. Summers, C. R. , and J. N. Murphy. 
 Noise Abatement of Pneumatic Rock Drill. 
 BuMines RI 7998, 1974, 45 pp. 
 
 4. George, D. L. , and N. J. Matteo. 
 Development of Noise Control Technology 
 for Pneumatic Jumbo Drills (contract 
 HO395029, Ingersoll-Rand Research, Inc. ). 
 BuMines OFR 100-81, 1980, 61 pp. ; NTIS 
 PB 81-237414. 
 
 5. Dixon, N. R. , and M. N. Rubin. 
 Development of a Prototype Retrofit Noise 
 
 Control Treatment for Jumbo Drills (con- 
 tract HO387006, Bolt Beranek and Newman, 
 Inc.). BuMines OFR 111-83, 1982, 
 106 pp.; NTIS PB 83-218800. 
 
 6. U.S. Mine Safety and Health Admin- 
 istration. Noise Control Abstracts. 
 Compiled by MSHA Health and Safety Tech- 
 nology Centers, Denver, CO, and Pitts- 
 burgh, PA, 1983, 45 pp. 
 
 7. Dutta, P. K. , and P. W. Runstadler, 
 Jr. Development of Commercial Quite Rock 
 Drills (contract J0177125, Creare Pro- 
 ducts, Inc. ). BuMines OFR 143-84, 1984, 
 114 pp.; NTIS PB 84-232644. 
 
 8. Dutta, P. K. , and W. N. Patterson. 
 Development of Noise Control Technology 
 for Jumbo Drills (contract HO395025, 
 Creare Products, Inc. ). BuMines OFR 21- 
 86, 1985, 67 pp. : NTIS PB 86-165081. 
 
35 
 
 9. Dutta, P. K. , and W. N. Patterson. 
 Development of Prototype Quiet Hard Rock 
 Stoper Drill, Volume I (contract 
 H0113034, Creare Products, Inc.). Bu- 
 Mines OFR 128-85, 1985, 63 pp. ; NTIS 
 PB 86-139722. 
 
 10. Patterson, W. N. Development of 
 Prototype Quiet Hard Rock Stoper Drill, 
 Volume II (contract HOI 13034, Creare 
 Products, Inc. ). BuMines OFR 20-86, 
 1986, 37 pp.; NTIS PB 86-165073. 
 
 11. Beranek, L. L. Noise and Vibra- 
 tion Control. McGraw-Hill, 1971, 650 pp. 
 
 12. Hawkes, I. , D. D. Wright, and 
 P. K. Dutta. Development of a Quiet Rock 
 Drill, Volume 2: Sources of Drill Rod 
 Noise (contract J01 55099, Ivor Hawkes 
 Associates). OFR 132-78, 1977, 77 pp.; 
 NTIS PB 289 716. 
 
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