For many years the problem of removing dust particles while drilling dry has confronted the mining and construction industries. In areas where water is not available, rock drilling is still being done under hazardous dust conditions. It was in an attempt to find a partial solution to this problem that the material contained in this report was compounded

Hardt, Norman J.

English

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Montana Tech Library Digital Commons @ Montana Tech Bachelors Theses and Reports, 1928 - 1970 Student Scholarship Spring 5-7-1954 An Investigation of a Dustless System of Dry Drilling Norman J. Hardt Follow this and additional works at: https://digitalcommons.mtech.edu/bach_theses  Part of the Mining Engineering Commons Recommended Citation Hardt, Norman J., "An Investigation of a Dustless System of Dry Drilling" (1954). Bachelors Theses and Reports, 1928 - 1970. 426. https://digitalcommons.mtech.edu/bach_theses/426 This Bachelors Thesis is brought to you for free and open access by the Student Scholarship at Digital Commons @ Montana Tech. It has been accepted for inclusion in Bachelors Theses and Reports, 1928 - 1970 by an authorized administrator of Digital Commons @ Montana Tech. For more information, please contact sjuskiewicz@mtech.edu. o T SCHOOL 0 t NESButte, MontanaNING 68IReport onTIG TI N OF AF D Y DILLINGDU TL25521by .._ t. (1 torof ssor K. Sto tByoJ. H rdt7, 1954Residence HallMontana School of MinesButte, MontanaMay 7, 1954rofessor Koehler S. StoutDepartment of Mining Engineeringontana School of MinesButte, MontanaDear rofessor Stout:In compliance vdth your request of Februar.y 8, 1954, I amsubmitting the following report to complete the required workin Mining 68.This report covers the progress attained by rese "rch intothe dust control problem of dr.y drilling. It is a continuationof a previous report,§ystem of Dry Drilling, that I submitted to you on Janu r.y18,195~ .•Yours truly,Norman J HardtJH.ehTABLE OF CONTENTS••••••••••••••••••••••••••••••••••••••••••••••CONCLU ION ••••••••••••••••••••••••••••••••••••••••••••••••~HOD OF ATTACK ••••••••••••••••••••••••••••••••••••••••••T18T DATA •••••••••••••••••••••••••••••••••••••••••••••••••ILLUST TIONSFigure 1, Venturi Tube Vacuum Pump ••••••••••••••••••Figure 2, Venturi Tube and Drill Steel ••••••••••••••FigureFi ureFi re3, Disassembled Swivel •••••••••••••••••••••••4, ssembled Swivel ••••••••••••••••••••••••••ump Showing Hose5, Vacuum ..................Fi re 6, Vacuum Pump in Operation ••••••••••••••••••Figure 7, D~ Drilling Modific tion •••••••••••••••••Fi re 8, Drilling Down Holes •••••••••••••••••••••••Figure 9, Drilling Breast Holes •••••••••••••••••••••i re 10, eldin FailureFigure 11, Lef't=hand Viein SVfivel •••••••••••••••••of Jack-leg Modification •••Figure 12, i ht-hand View of Jack-leg Modification ••Fi ure 13, Test Drilling •••••••••••••••••••••••••••••igure 14, Brazing Failure of S~vel •••••••••••••••••Figure 15, Sketch of Venturi Tube ....................igure 16, Venturi Cap and ozzle ....................Fi ure 17, Timkin Finished Thread ••••••••••••••••••••Fi e 18, Hollow Drill Steel •••••••••••••••••••••••Figure 19, Swivel ••••••••••••••••••••••••.•••••••••••FiRur 20, Compres ed ir jector st s •••••••••••• •. age 113699101011111212131314141515161718192021AN INVESTIGATION OF A DUSTLE S YSTOF DRY DRILLINGINTRODUCTIONFor many years the problem of removing dust particles while drillingdry has confronted.the mining and construction industries. In areas wherewater is not available, rock drilling is still being done under hazardousdust conditions. .It as in an attempt to find a partial solution to thisproblem that the material contained in this report was compounded.CONCLUSIOAs can be seen from the accompanying ictures, the method used inattacking the dust roblem in drilling dry was unexpectedly successful.Under the assumption that a rock drill could be altered to vacuum cleana drill hole; the following modifications, as shown in Figures 1 through14, ere adapted to a sinker type drill and to a new air-leg combinationdrill. A screw-on Timkin bit, type nDIt thread, with one large center holewas attached to a piece of 1-1/4 inch outside diameter electric seamlesstubing. This tubing, approximately 36 inches long and 7/8 inch insidediameter, was machined as shown in Figure 18, with a Timkin 1-1/4 inch "DIIthread at one end and a 1-1/4 inch G-D long-hole drill thread at theother end. To the rear end 0 this hollow drill steel was coupled a ffi~vel,shown in Fi ures 3, 4, d 19, to remove the dust before it reached therock drill. A one inch reinforced ru~ber hos connected the swivel dis-charge to a Venturi tube vacuum pump (Figu~es 5 and 7). Sufficient vacuumpressure was obtained by cin a 3/16 inch co 1 r-eseed air nozzle into acritical po ition in the Vent r: tube.ile the actual dril:!'l1 done WaS lj i+.e ~ ce-ca se of failure of-1-unhardened steels and amateur Telding and brazing (Figures 10 and 14),this theory of dry drilling ...ras observed to work exceptionally well. Nosign of dust or rock particles was apparent near the cutting face. Tre typerock drilled was a Quartz lonzonite and pieces over 3/8 inch in diameterwere observed being dischar ed from ~he vacuum pump. There was, further-more, no Sign of clogging or hinderence of dust particles anywhere in thedischarge line from the rock bit to the vacuum pump.Because'a standard hex drill shank is welded onto the swivel, it caneasily be slipped into the chuck of a sinker or an air-leg with no additionalmodification. It is apparent, with results obtained from the testingoperation, that the drill steel and swivel can be of smaller diameter,possibly one inch outside diameter and 5/8 inch inside diameter, and stillwork successfully. It is doubtful that much less than a 5/8 inch insidediameter ho e in the drill steel would permit passage of sufficient airve oeities through the steel and the swivel to effectively carry away allthe dust with the type vacuum pump used. For discharge air volumes an~static pressure in inches of water of the'vacuum pump, reference is madeto Figure 20.There has be n some disagreement among local engineers concerningthe coolin ch acteristics of this vacuum drill. The theory has beenex ressed th t the volume and velocity of dry air actually moved bythe vacuum pump ould e· sufficient to a equately cool the rock bitdurin deep-ho e drilJing. This concept wou~d be difficult to prove ordis rove Without extensive additional drilling tests. However, during thelimited actu 1 rilling conducte , there was no si of excessive heatingof rock b·t or d ill st el.-2iETHOD OF AT CKThere have been a number of dustless d~ drills designed in the past,but fe have been even partially successful. Only the HolmanDRYDUCTORdrill, of British desi ,has comeclose to being satisfactory. The bigtrOUble "tvith the D YDUCTOis its reported inability to draw dust fromdownholes. It is IDlf belief that part of the difficulty of the DRYDUCTORcould be corrected by enlargin the inside diruneter of tte steel from 3/8inch to 5/8 inch. Reference as to the size of the DRYDUCTOR steel is froma letter of the Goodman Ianuf'acburtln Com'any.It las decided to use 1-1/4 inch O•• and 7/8 inch I.D. seamlesstubin for the purpose of this exp riment. It was felt that the low resist-ance fetor of this 7/8 inch I.D. steel would permit passage of sufficientvolume of air to effectively carry all the dust pa rt.Lc.Lesfrom the cuttinge e of the bit. An article, appe ring in the En and :Mi.nincone rnin the use of seamless tubing s drill steel is quotedas 0110\'15:II ew An 1e in Drilling Researchtl"By ay of explo ing t e ossibility of cut.tin drilling costs stillf rther, a mid-vest rn operator rec nt1y started experiments using 1-1/4inch se ~ess electric steel tubing in pl ce of drill steel. This tubingwas shanl{ed an Re ul s wi h the first trial batch of about 5000oun S W re ve~ s t·sf cto~. he foota drilled before breaking wasabout, hOO feet co re rth a? ro tely 112 feet obt ined vdth con-v~nti 1 rill steel. orne1-1/8 inch tubing was then tried but ·th veryun t·s ac 0 re u t ,the ason 0 t i f ilure being as yet unknown.3the company is now st.arlin a new series of tests 1.nththe 1-1/4 inchtubing, thinking it may shed some light on the failure of the smallertubing.nlAs is sho NIl in Figure 2, t11e steel used in this experiment was oflarge inside bore. This drill steel, of slightly longer than starterlength, was threaded for a 1-1/4 inch Timkin "Dflbit (1-7/S inch acrosscutting edge). Detailed dra\iings of this Timkin thread are found inFi ures 17 and 18.The drill steel was desi ed to couple to a swivel, so the rear endof the drill steel was threaded vith a 1-1/4 inch long-hole coupling, No.CL5-400-GD, purcha ed from the Gardner Denver Company of Quincy, Illinois.One end of the swivel shank as also threaded to receive this Gardner Denver1-1/4 inch coupling. Into the other end of the swivel a 4-1/4 inch standardhex drill steel shank (Figures 3, 4, and 19) was weLded whi.chenabled t.rehollow steel and swivel to be slipped into the chuck of an I.R. Jackleg.PreVious to this, a 3-1/4 inch drill shank was welded into the swivel endto permit installation onto a standard 3-1/4 inch chuck equipped sinkerdrill.Ttle swiv 1 h t '\; chined to 1.250 inches for a distance of 7inc es rneas red rom the end of the G-D long-hole thread, and then shouldered.Into this machined surfacerot ting round the shaft,ere drilled five 3/8 inch holes 90 degrees aparts shown in Figures 3 and 19. These 3/8 inchholes ermitted the int rrupted f ow'of dust particles from the drill steelto h outer swivel sleeve. hi outer sleeve was fabric ted from a pieceof te 1 pipe m asurinlong Circular piecepro imately 2-1/2 inch I.D. d six inche.sof 1/4 inch p te me suring 2-1/2 inches in diameter4were brazed onto the ends of the pipe sleeve and then bored to 1.6000 inches.Brass sleeve bearings measuring 1.250 inches I.D and 1.600 inches O.D.were machined to permit the outer sleeve to ride free on the rotating imlerswivel shaft. These bearings, as shown in Figures 3, 4, and 19, have anactual outside bearing length of 1/2 inch and another 1/2 inch of shoulderthat tends to hold the outer sleeve from sliding horizontally on the swivelshaft This shoulder is approximately 1-3/4 inches in diameter and is heldfi~ against the swivel sleeve by the G-D coupling at one end and theshoulder of the swivel shaft on the other end. In the side of the swivelslee e, a one inch bored hole permitted the inserting and welding of a pieceof 3/4 inch standard pipe six inches long, to whioh the discharge hose canbe attached.To this 3/4 inch pipe a length of one inch noncollapsing rubber hoseWas attached (Figure 7and 8) The other end of this hose was attached tothe intake side of the vacuum pump (Figure 5). The pump, of oourse, is aventuri tube with comD~es ed air nozzle inserted in a critical position.;&;It is the high pressure air ejected through this nozzle into the venturichambe that causes the vacuum effect. This partial vacuum is actua~small in inches of mercury, but produces a high volume of air throughthe venturi tube. It is the volume and speed of the air rather than thepressure difference that makes the venturi tube an effeccive pump for thisarticul r experimental design. It can be seen from the graph on Figure 20th t 500 cubic feet of air per minu e is obtained through this venturi ifthe design specifications are followed. Figure 15 of this report shows adetailed plan of the venturi tube used in his design. Figure 6 shows thisVenturi pm p in operation5Further, it i planned to discharge the dust from the rear of thev nturi throu h a cloth b to a permanent dust collector underground, andinto the atmosphere somedistance from the drill for surface operations.T T D TAThroughout the month of November, 1953, the venturi pump was testedfor its ability t.o pi.ck up and dispose of extensive amounts of various sizedust particles. Difficulty in obtaining sufficient air pressure from avail-able compressors made these tests r ther inconclusive. Results of Test 1on ovember 6, 1~53 are quoted as follows:IITest 1 Nov. 6, 1953 1:30 PIll"1. Air pressure limited to 50 ~bs. (Upper cutoff at 50 lbs.)2. Volume of air used with 3/16 inch dia. nozzle is under 160cubic feet per minute.3. t this pressure the size of p rticles is of no immediateconsequence Particle 3/8 inch dia. are picked up withno ap rent difficulty.4. Incre e in air pr sure ~ould undoubt dly increase weightand vo urne of ust particle picked up each minute.S. It is n ted that the com ressed air nozz e is of too lighta te i 1 (structural y) to with tand ending strains.T e nozzle dll probably ave to be made of 3/16 inch(in ide) he ~ du y st el pipe.6 0 inc ho e i al 0 too hevy fo the lig t wei ht of theventuri tube, both t t e high essure side and at thev cuum ide.7. scs we e to ed a 3:45 m./ N. J. Hardt."Tests conducted during the month of pril, 1954, with an air pressureof 100 psi, have sho that the venturi pump can easily handle all theeight and volume of dust rticles that it might be confronted with duringordinary drilling operations. Results of Tests 5 and 6 are quoted as follows:"Test 5 ril 23, 1954 1:30 pm"1. ir pressure steady at 100 psi.2. Dry Drill ~odification installed on a sinker drill (Figure 7).3. Compressed air line and vacuum hose hooked up to venturivacuum pump (Figur 5) •4. Bre - holes drilled into u rtz- onzonite wall (Figure 9).5. V rtic 1 holes also drilled into cement andbrick floor (i re B).6. 11 dust particles, includin pieces 3/8 inch indi ., were emoved succes u ly from the cuttingface (Fi re 6).7. At 2:45 pm the swivel piece developed a Telding failureat the junction of th swi.ve.Lshank and re hex drillshank (i re 10) •• Test cone ude t 3:00 pm.9. 'itnessed by ro e or Koehler tout and re resen-tatives of a local machine hop, ( at es on request).s/ N. J. Hardtpril 23, 1954"-7-ttTest 6 April 28, 1954 1:00 pm"1e Air pressure steady at 100 psi •.2. Dry Drill Modification installed on an air-leg(Figures 11 and 12)3. Compres air lin d vacuum hose hooked up toventuri vacuum pump (Reference to No. 3 in Test 5,See Figure 5)4. Breast holes drilled into uartz-Monzonite wall byan air-leg (Figure 13)5 All du particle w e removed successful~ fromtIle cutting face.6 t 2:30 pm a br zing failure developed in swivel sleeve(Figure 14), nee ssitating future welding instead ofbrazing on all part here ~ appreciable stress willbe felt It was also assumed that this failure was theresult of binding caused by excess bending of the softtubing used in lace of regular hardened drill steels7 Te ts concluded at 2:45 pm.B itnessed by rofessor Koehler tout, Robert Hall,repre entatives of t 0 rock drill manufacturers, andthe superintendent of local machine shop (Name on Request)./ J Hardt·April 28, 1954"Fig. 1 Venturi Tube VacuumPump'Fig 2 Venturi Tube and Drill Steel·th unfinished Swi e1-9-Fig. 3 Disassembled Swivel ShowingComponent Part sFig 4 ssembled ·vel Coupl d to Drill Steel by1 1/4 t CL5--400 D Co pIing-10-Fig 5 Vaouum Pump Showing Vaouum Hoseand Compressed Air Lineig 6 Vacuum Pump in Operation-u25521Fig 7 Dry Drilling ModificationInstalled on Jack Hanmerig 8 Jack HanmerDrillingown HoleFig. 9 Drilling Breast Holes witha Jack Hammerg 10 Arro Showing Welding Failurein Swivel hankl3Fig. 11 Left ..hand vie of Dry Drill ModificationInstall on Ja klegFig 12 Right hand view of Ja kleg odificationFig. 13 Test DrillingFig 14 Brazing ailure of Swivel-15--115Venturi Tube+:::*" 13dia.:::_N~Q..).EIe)............~u> .(1)~ enI!--" to:.1QJ~lr)~Q) en\...~~ N\D~ N.f._)N N~.~ 00co ~J.....a-~=~ r). 16 Venuri p and ~ozzl....17Q.DIAl.~WoW.~UlLL t!1o Zza wz ~L.U «I.o ~w UJot<1 «w.~I~F~ 17 Timkin Finished Thread18N00.(3 +10CO-.N00Q. +10r:0,..JWw Ql-V).£ IJ1%_Jwwf- AU1 H~eo.....J r.-_J<0:: QCl 0~'<):5 ~'--0__j_J0:ri 18 HollowDrill Steel-19........ ~F~gure 19 Swivel-20-II\.~ -'~==I~ ~~I--Ilo=~ "F--+,,=jF-l--+--iI-+-+-+c !'==.~-.= =. ._-'. ,.=~-li---~lli---=lr=~~~=:'~"}-+-'r--F=1- =t-r="H=·i~t-.....,_...~t-r-t-t~i-r~~f'-Fi-+-+-+-+-i-+-"H~-J-.<~-4-~-\-o:....,.-~~-H~~~~=~~~~~-~~~~P~'--+~~=4'~i'==i:-~t !=:F:~c~r~-r~~~h~~~~-r~~~~~'~-++~~'-'-+~~~~~~++-~~~'~~!II~i~~,cl~~-'~.=-'~=;:::~-;"~~ry==~'=C-=i~-~'~'~~i'-~~~=~i~=~'~=I.=;~~~~:~~:~+~~r~~~~;;-~~·~-~~·Fr~~=rt~rT~~4-~~r~irr·t~~~-~+-~~~-1r~~'~~~~~I--I~;(·-----cc-.l:-:-.;-._~,-.=.. ~.---l'~:-;~'cc ·-~:,;;..=·.y'!'I---'O:~l~:I~==.: ~I~1d.-L=t-!"=~:=~~;::::::;:~~.=j':,:t~'·~:+~:~.,I~~I~r:,':,~~~:-=O-~l~.,.'-;~ol~m er~ ; R= 1¥I-J4H-1-r-t-t-t-t-+-t-+-i-1t-t-'+-+-'_i-~f.-~'44'~1I~!~~~~~~-~-~'~~;~'I'(I~'~~~~F~~~~~'~*~~~=~=::=~~~~~~' -~~II II

An Investigation of a Dustless System of Dry Drilling

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An Investigation of a Dustless System of Dry Drilling

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