WATER JET CONFERENCE - Waterjet Technology Association

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DISCUSSION OF FLUID MECHANICS The intent of this work was to modify an ordinary, continuous jet for the purpose of improving cutting ability at long distances from the nozzle. The Percussive Jet was an example of a fundamental modification of such a jet. The knowledge which has been accumulated so far is not complete but represents a first investigation into this area. The information was taken from infra-red transmitted light photography, scattered visible light photography, force or impact gauge measurements, visual inspection of Jet impacts on concrete block test specimens, and a limited amount of mathematical modeling. The Percussive Jet can take an ordinary jet and transform it into a bunched jet several times as wide. An example is shown in Figure 3 where the outside diameter of the Jet is increased five-fold (from 1/2-inch to 2 1/2 inches. Since aerodynamics is the principal mechanism acting to destroy ordinary jets, making a jet "fatter" would seem to be the appropriate action to take to protect the jet so it can operate at long standoff distances. However, the actual mechanism which occurs in Percussive Jets is more complicated and interesting than this simple explanation. In actuality, a protective shroud of water droplets seems to be created around the core and bunches of a Percussive Jet. The real novelty is that this shroud is created and maintained at the average velocity of the Jet, U SO . Figure 2 is useful in visualizing this phenomenon. In this sketch, the Jet is travelling at average velocity U SO from left to right. Wavelength is L considering f as the predominant frequency of modulation. The original diameter of the Jet is D o. As discussed earlier, the faster portion of the Jet overtakes the slower region and a radial velocity component U R is formed and produces radial bunch growth. Aerodynamic drag shears off some water from the outside extremities of the bunch. Since the bunch is travelling with axial velocity U SO, this "sacrificial" water is sheared from the bunch at this velocity. This water which is sheared from the bunch forms a shroud around the Jet to help protect it from the disruptive influences of aerodynamics. An estimation of the axial velocity profile is shown. Although no distinct boundary between air and water droplets surrounding the Jet exists, a shroud envelope is sketched to illustrate the radial extent of a water-rich area. The central core of the Jet between bunches is "tight" in diameter and relatively quiescent with some minor protuberances resulting from Rayleigh instability, noise in the modulation signal, and feedline dynamic effects. From a fluid mechanics point of view, two points are most interesting. First, the shroud is created by water sheared from the outside edges of the bunches which are travelling at velocity U SO. Therefore, the shroud is travelling at a velocity approximately U SO. Hence, this gives an example of a Jet shrouded by water drops which is travelling along and being constantly recreated (200 - 1000 times per second) at the velocity of the Jet. (Shrouds which have been discussed in the literature are created by expelling water 31
or air in the vicinity of the discharge nozzle only. These shrouds rapidly lose momentum and are slowed down by aerodynamic drag.) Second, the presence of vortices or eddys downstream of the bunches cannot be detected. Such a phenomenon would be expected from the fluid mechanics of blunt bodies travelling through a viscous medium. The absence of such effects is considered to be due to the sacrificial loss of water from the bunch to the shroud and to the repetitive nature of the Jet. With this brief explanation as background, examination of Figure 3 is illustrative. This photograph shows an infrared photograph of a Percussive Jet discharged at 500 psig and travelling from left to right at 330 feet/second. The bunches are most optically dense and appear dark. The flow around the Jet is caused by scattered light from the mist surrounding the Jet. The Jet appears to be starting to separate just upstream (to the right) of the bunch because optical density is diminished in this area. Ligaments are being sheared off the outer edges of the bunches. These ligaments are not swirling or forming vortices but are coming back in gently curving lines. Although some protuberances appear on the central core of the Jet, the central core still maintains a "tight" 1/2 inch. In Figure 4, the discharge pressure has been increased to 2000 psig. The Jet is now travelling at 500 feet/second. The mist around the Jet is confined to a more restricted radial dimension, as would be expected with higher velocities and increased aerodynamic drag. The angle the sheared ligaments make with the core of the Jet is much less than that in the previous photograph. Again, no vorticing or eddy flow can be seen. Separation of the core of the Jet from the leading edge of the bunch is more evident. The central core of the Jet looks "tight" and relatively undisturbed. If Percussive Jets are slowed to about 200 feet/second so that the mist surrounding the Jet can be reduced, these jets appear to the eye to be quite different than ordinary jets. An ordinary jet looks like a homogeneous mist, whereas a central core or line can clearly be discerned in the Percussive Jet stream. As an example of a Percussive Jet operating at extremely high amplitudes, Figure 5 is a photograph taken using scattered light. This view is helpful in understanding the fluid mechanism which allows the Percussive Jet to persist to larger distances from the nozzle than ordinary jets. The Jet is travelling from left-to-right in this photograph. The Jet velocity was extremely low so that the mist that surrounds high-speed Jets would not interfere with photography. however, the amplitude of the Percussive Jet was set very high to illustrate this effect (the amplitude is so great that these conditions would have questionable practicality in the field). This photograph shows the bunching process creating protective "umbrellas" around the Jet. As these umbrellas move away from the nozzle, they grow in diameter and aerodynamics gradually shears off ligaments of water at their extremities. These umbrellas are about four inches in diameter and are five inches apart. The central core of the Jet is 1/2-inch. 32
Page 1 and 2: Proceedings of the Second U.S. WATE
Page 3 and 4: Visualization of the Central Core o
Page 5 and 6: A Status Report on the Conceptual D
Page 7 and 8: SESSION 7 - CIVIL & INDUSTRIAL Chai
Page 9 and 10: Cutting Hard Rock With Abrasive-Ent
Page 11 and 12: frictional and piping component rel
Page 13 and 14: R = a1 ⋅ A1 A2 a2 I = 2H o Q o
Page 15 and 16: attenuation of the output. The tran
Page 17 and 18: Figure 1. Branch System Modulator F
Page 19 and 20: Figure 5. Modulation Response for B
Page 21 and 22: Figure 9. Modulation response for s
Page 23 and 24: can be used for any form of input.
Page 25 and 26: with a cylindrical shape to the jet
Page 27 and 28: m/s. The range of power found from
Page 29 and 30: Figure 3. Power vs nozzle diameter
Page 31 and 32: Figure 5. Frequency vs length of th
Page 34 and 35: NAME: Gerald Zink COMPANY: StoneAge
Page 36 and 37: modulatornozzle assembly. The ordin
Page 40 and 41: This process serves to protect the
Page 42 and 43: For test purposes, these concrete b
Page 44 and 45: REFERENCES CITED 1. Barker, C. R.,
Page 46 and 47: FIGURE 4. INNER CORE OF PERCUSSIVE
Page 48 and 49: FIGURE 9. EXAMPLE OF HIGH-PRESSURE
Page 50 and 51: NAME: John E. Wolgamott COMPANY: St
Page 52 and 53: THE FOCUSED SHOCK TECHNlQUE FORPROD
Page 54 and 55: The reflected wave is thus also cyl
Page 56 and 57: neglected. The introduction of a co
Page 58 and 59: DISCUSSION NAME: George Savanick CO
Page 60 and 61: H’ mean shape factor Hj theoretic
Page 62 and 63: Required streamline curvature at th
Page 64 and 65: 2 x 2 ≅ ( e − 2 p + w)/k2 (2-8)
Page 66 and 67: eliminating 2 n r 2 from equations
Page 68 and 69: approximation to the actual flow si
Page 70 and 71: skin friction coefficient but are c
Page 72 and 73: where: (H) = A1H 3 + A2H 2 + A3H +
Page 74 and 75: effect (< 0.5%) on coefficients of
Page 76 and 77: TABLE 5 Rei x 10 5 β 3 4 5 6 Po Po
Page 78 and 79: TABLE 6 D(mm) d o(mm) L t(mm) L f(m
Page 80 and 81: expanding rather than contracting a
Page 82 and 83: 25. Weber, H.E., 1978, Boundary lay
Page 84 and 85: Figure 5. Wall velocity distributio
Page 86 and 87: Figure 9. Effect of nozzle design o
Page 88 and 89:
Figure 12. CA+T Design Philosophy.
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Figure 16. Effect of inlet b 1 cond
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Figure 20. Relaminarization at nozz
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Figure 24. Pressure decay data. 88
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VISUALIZATION OF THE CENTRAL CORE O
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DISCUSSION Although employing the i
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5. Lambert, J. H., 1760, Photometri
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Figure 6. Spectral sensitivity curv
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NAME: W.C. Cooley COMPANY: Terraspa
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INTRODUCTION Pulsed liquid jets sho
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y=X ∨ P A dy = p p A p 2 (L c y=0
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Using equation (15), the value of X
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Thus about the first 10% of the dri
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Many design cases, including those
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surface spall occurred, resulting i
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Figure 3. Chamber pressure at pisto
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Figure 7. Effect of nozzle area rat
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Figure 11. Extrusion device schemat
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Figure 15. Typical chamber pressure
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DISCUSSION NAME: W. C. Cooley COMPA
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material which are, in turn, affect
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the water jet. This method was not
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where h is the depth of penetration
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obtained during this phase of the i
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observed that the smallest depth of
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Figure 2. Idealized Relationships b
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Figure 6. Penetration as a Function
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DEVELOPMENT OF VARIABLE DELIVERY TR
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THE STRUCTURE AND FUNCTION OF THE P
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The injection pressure can be contr
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ACKNOWLEDGEMENTS The authors gratef
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Figure 4. Theoretical required powe
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Figure 9. Variation of efficiency w
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THE "SKIPJACK" SEWER CLEANING NOZZL
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HYDRO-BLASTING SAFETY C.W. Adaway,
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Remember, your Hydro-Blasting work
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horizontal, sometimes vertical, and
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Figure 2. Safety Gear Figure 3. Tub
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DEVELOPMENTS IN CLEANING COKE OVEN
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causing chain breakages and the scr
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was encountered, then the rotation
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(C) Capital Expenditure: Material i
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Figure 9. Swivel coupling Figure 10
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OPTIMIZING JET CUTTING POWER FOR TU
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PRESSURE DROP (psi) ELEMENT Cv @10
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power output. Undersized nozzles re
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Subscripts n - Nozzle p - Pump t -
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Figure 1. Cutting effect as a funct
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CONSIDERATIONS IN THE COMPARISON OF
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pressure can be lowered to perhaps
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Figure 2: Fan jet issuing from a no
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DISCUSSION NAME: John Griffiths COM
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where Q = Flow rate - gpm D = Jet O
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Again, not limited to Newtonian flu
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REFERENCES 1. Brown, R.W. and Loper
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Table 2. Jet Cleaning Speeds and ot
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ANSWER: The utilization of the stat
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complexity and short component life
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Figure 4, for ap values ranging fro
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Decontamination Methods for rapidly
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a. “PULSER” b.”ORGAN-PIPE”
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Figure 5 - Removal rate for various
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DISCUSSION NAME: David A. Summers C
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DRILLING BORE HOLES IN COAL MINES U
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pile could not be judged as represe
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DISCUSSION NAME: David Summers COMP
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HYDRAULIC MINING EXPERIMENTS IN AN
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The monitor was fed pressurized wat
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The IH rig was considered to be sup
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REFERENCES 1. Okhrimenki, V. A., A.
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Figure 2. Jet cutting sandstone at
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Figure 5. Schematic plan view of In
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Figure 7. Suction Box. 226
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USE OF HIGH PRESSURE WATER JETS FOR
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flame torch to cut this block, redu
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the order of 360 rpm. Under these c
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Figure 3. Slot cut by jet at 11 o s
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JET-MINER SURFACE AND IN-SEAM TRIAL
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The hydraulic drive of the haulage
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The surface trials had have the obj
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Figure 2. Experimental version. Fig
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Figure. 7 Jet-Miner prototype Figur
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SOME PATTERNS OF TECHNOLOGY TRANSFE
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Development of High Pressure_Techno
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configurations, the design of an op
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and public sectors. After a haitus
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Souder, W.E. and Evans, R.J., "The
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Figure 5. Technological achievement
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Table 3. Perceived disadvantages of
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already been, or is being applied w
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Using the requirements profile and
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ant hose combination, a guiding sys
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HYDRAULIC MINING TESTS Site selecti
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SAFETY All operations were carried
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TABLE V. Categories of Jet Mining D
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Figure 2. Generalized geologic prof
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SECONDARY FRAGMENTATION WITH WATER
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do possess a maximum point (Fig. 8)
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Figure 4. Rossin-Rammler plot. Figu
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Figure 8. Non-dimensional plot for
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HYDRAULIC COAL MINING SYSTEM Typica
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Figure 4. (From ref. 1) DISCUSSION
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INTRODUCTION Developing an unique t
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The coefficients "b " in Eq. (1) ca
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By the end of 1982, a total of more
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Figure 4. Cutting ability of swing-
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Figure 10. An operating performance
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for an abrasive, the abrasive parti
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the particles, while at slower spee
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to break away the remaining segment
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Table 1. Concrete saw technology. T
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NAME: Tom Brunsing COMPANY: Foster-
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FEASIBILITY STUDY OF CUTTING SOME M
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hydraulic power required to cut thr
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pressure was varied from 103 to 310
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2.1 Heading and gutting fresh cod f
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Figure 5. The cuts surface of a blo
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Figure 17. Cuts made across the cla
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JET NOTCHING USED IN THE CONSTRUCTI
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Bottom notch diameter was determine
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σ H = in-situ stress in the horizo
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Figure 3. Final block displacement.
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Figure 8. Comparison of Slurry Pump
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THE FURTHER DEVELOPMENT OF AN UNDER
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use taps or hydrants. To achieve th
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supply line. It was determined that
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The rotating head requires major mo
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Figure 4. System field test set-up
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Figure 10. Bentonite drilled clay s
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MECHANICAL TOOLS Cutting Tool Energ
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Ψ = cos −1 ⎧ ⎪ ⎪ ⎨ ⎪
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mode also contributes to chip flush
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NAME: Simon Johnson COMPANY: Newcas
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ROLLER TOOLS COMBINED WITH HIGH-PRE
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Various designs and applications ar
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Figure 1. Full-face tunneling machi
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Figure 11. roadway profile cutting
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Figure 19. High-pressure water jet
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DESIGN AND OPERATION OF TWO LARGE-S
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The hydraulic system for the thrust
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Results of Trial Tests As part of m
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cutting rates, degree of bit wear,
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Overall approximate Weight: Basic M
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Figure 5. 3 ft. diameter laboratory
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nozzle diameter and cutting speed w
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2. Cutting Speed The influence of c
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energy it effects an increase in me
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Tip angle (degrees) 87 Off-set angl
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Figure 5. Figure 6. Figure 7 Figure
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Figure 17. Figure 18. Figure 19. Fi
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SCHEMES OF COAL MASSIF BREAKAGE BY
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out thoroughly an efficient scheme
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Research analysis has proved that t
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DEPENDENCE OF POWER INDICES OF COMB
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The experiments have shown how the
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K Ay = coefficient correcting for f
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Figure 1. Schemes of combined break
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Figure 5. Dependence of specific en
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Figure 12. Percentage of grade R -6
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Figure 1. Particle size analysis. T
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NAME: Dr. Henkel COMPANY: Bergbau-F
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presented. This study, of course, i
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identifying a general trend for the
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Effect of Abrasive Hardness, Shape
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In some situations, especially in c
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Figure 1. Abrasive waterjet nozzles
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Figure 8. Effect of standoff distan
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Figure 13. Abrasive waterjet cuts i
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CUTTING WITH ABRASIVE WATERJETS M.
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3.3 Abrasive Feed Systems For abras
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Because of the large number of infl
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due to wear. Although actual operat
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from this new technology. Table 2 l
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Table 1. materials cut by abrasive
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Figure 1. Abrasive waterjet nozzles
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a) kerfs in mild steel b) S.S. 15.5
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a) circle cutting in glass b) lamin
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DISCUSSION NAME: Andrew F. Conn COM
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CUTTING HARD ROCK WITH ABRASIVE-ENT
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slurry nozzle. Testing at water pre
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DISCUSSION OF TEST RESULTS Jet Conf
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materials. The flexibility in nozzl
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pressure can be wiped out if diffic
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9. Maurer, W.C., and Heilheckler, J
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Figure 5. Effect of abrasive feed r
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Figure 9. Accumulated depth of mult
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Figure 13. Close-up view of quartzi
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ABRASIVE INJECTION USAGE IN THE UNI
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sudden changes in the feed rate eff
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or the abrasive must be manually to
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clog; there not being sufficient ar
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CODE OF PRACTICE FOR THE USE OF ABR
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Figure 5. Water abrasive cleaning h
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Figure 15. 360 0 abrasive pipe clea
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ECONOMIC CONSIDERATIONS IN WATER JE
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Other criteria to be considered in
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3 MANUAL METHODS OF JET CLEANING &
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contractor with old, unsafe, equipm
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Figure 1. Showing the increased cos
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Figure 8. Automatic tube bundle cle
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ackground to the subsequent coopera
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The molecules of SUPER-WATER posses
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shaken just before use. SUPERWATER
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26. Bednarz, L.P., "Effects of Poly
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