No. 8951 V s\ • —•-% /^^y^ >°/^w.°- a*^/** ^ ° - ° <& VV ^°- 'bv* v°V ^% V^ 1 ♦ v ^ ,^- ,\ ***** ?m&>^ "++$' •-^B'- "^1^ .""iSB^*- ^o<" ?-^iK- ^ov* v v ^. ; . , +_ *b? \^"'°A* A 9* a ^q* -.*• ^ * ^ O' cv » • ^BSSVs Sws w» m HFiI i ft & f Pi P i ■lllflrJifl 1^ ' * . * : *i * : i' i I I f I ■ Iffln I m * § f ( f : £ I f 1 1 f 1 § HHilili till ill .^ a aK S ■ :;w -M M $ FIGURE 21. - Sample face showing constant-kerf- length tests (i.e., transverse cut with fixed depth of cut, new cut each pass). FIGURE 22. - Frictional ignition test chamber milli- seconds after frictional ignition. structural I-beams with horizontal beams cemented in the floor between the up- rights in the same manner as the top crosspieces to form a box shape. Such an arrangement provides stability for locking the microminer or any other test apparatus in place during tests. The sample support section, shown on the right side of figure 23, has two horizon- tal crosspieces mounted between U-shaped brackets on the uprights and held by 5.08-cm pins. These provide the backing for the normal forces imposed upon the sample during cutting. The horizontal cutting force is supported by the steel beam in the floor to which the uprights are welded. A simulated coal material has been de- veloped for this test bay since it is not practical to obtain coal in the sample size necessary. A complete description of this synthetic material is contained in a following section. Although respirable dust measurements cannot be directly obtained from the sim- ulated sample, relative differences can be obtained by shrouding the entire test bay and mounting a quick response sampler inside the cutting area. To ob- tain cutting forces either the test equipment or the sample support system must be instrumented. This large test bay is presently used with two systems: the linear cutting retrofit microminer and the in-seam tester. Microminer Multiple-Bit Linear Cutter The original research microminer (6) has been modified by replacing the nar- row, rotary drum section (now being used in the ignition-wear test facility) with a multiple-bit head which makes linear cuts (fig. 23). The machine is designed for deep linear cutting with multiple bits. One of the bit mounts is instru- mented to obtain orthogonal cutting forces. In use, the machine is trammed and locked into position in the test bay by front and rear roof jacks. The rear roof jacks have a canopy to cover the operator's station. In the bay these roof jacks are set against the cross beams that simulate the top and lock the machine in place. The bit-block mounting combination is designed for a maximum 12.7-cm depth of cut over a maximum ver- tical distance of 198 cm. 19 FIGURE 23. = Microminer in large sample test bay. Bit force instrumentation consists of Assembled size: three strain-gaged clevis pins which at- Length 50 in. tach the bit mounting block to the four- Width 18 in. bar linkage that retracts and extends Height 42 in. each bit. The bridge outputs are re- Assembled weight 250 lb. solved into components of normal and Hydraulic power required at cutting force and summed electronically. 1,500 psi: The data are available as analog outputs Face preparation 10 hp. or digitally in binary coded decimal Test cuts 2 hp. (BCD) form. Power for instruments Battery Maximum cutting force 3,000 lb. In-Seam Tester Maximum cutting length 20 in. The in-seam tester (1ST) (fig. 24) is a Additional supporting equipment (packing Bureau-developed portable device that can cases, spare parts, hydraulic rotary im- be carried to an underground face for pact drill, etc.) adds 250 lb to the to- measuring orthogonal cutting forces in tal system. The heaviest single item, situ (fig. 25). Additionally, the device the cutter with hydraulic cylinder and has a shroud that can be used with a supporting structure weighs 150 lb. rapid-response optical particle sizer to obtain primary dust data. This total Bit forces are fed to the support system provides direct laboratory-field structure through a splined shaft instru- test correlation since portability takes mented with strain gages to measure it to any environment. An underground normal and cutting force. A portable face after cutting with the 1ST is shown data acquisition system digitizes and in figure 26. Specifications of the unit stores the data, which are then read follows: 20 FIGURE 24. » ln°seam tester in use underground. out as a time-at-load-level histogram. Energy, mean force, and peak force can be determined from the histogram. It is anticipated that data produced with the 1ST will enable designers to select pick types, spacing, lacing, depth of cut, and rotary speed for specific coal types and seam conditions to improve cutting performance. In preliminary field tests already completed, one operator indicated a 15-pct increase in productivity by reorienting direction of cutting in the seam. While the Bureau is not yet ready to make such claims, since the device is still a research tool, it is already apparent the 1ST has great po- tential for helping operators improve the coal-machine interface to properly match machine characteristics to the seam characteristics . DIGITAL ACQUISITION SYSTEM A Digital MINC II system is available for data acquisition, processing, and storage. The system is based on the PDP-11/23 8 processor with the KEF11 floating-point chip. Peripheral storage is provided by a dual drive RX02 floppy 8 The terms "PDP," etc., are the manu- facturer's terminology and have no spelled-out equivalents. diskette system and a dual-drive RL02 hard disk system. A total of 21 M bytes of random access storage is provided. User interaction with the system is through a VT105 video graphics terminal. Hard copies of video displays can be made on a Tektronics model 4632 device. In- terfacing with the system is accomplished through RS232C ports, an IEEE instrument bus, and MINC input-output modules. 21 FIGURE 25. • ln=seam tester cutting coal underground. 22 FIGURE 26. - Face area underground after testing with in-seam tester. The modules presently include an A/D con- verter, a preamplifier, and a program- mable clock. The system operates on MINC basic V.2.0, which includes routines for data acquisition and analysis, graphics, and IEEE bus support. SAMPLE PREPARATION COAL The need for a constant supply of test samples requires both field acquisition and synthetic coal preparation. Field samples are sent to the Bureau; each is usually encased in gypsum for easy stor- age and handling, and to allow a stiff mounting in the cutting fixture, or to hold it at the proper bedding plane ori- entation. The coal soon changes from its in situ condition after it is left exposed in the laboratory environment. For further protection, the encased coal is stockpiled in a 90-pct-humidity room; as an alternative, raw coal may be im- mersed in water until needed. It will then be encased in gypsum 15 to 30 days before testing. Gypsum is used as the encapsulating material because the form used neither contracts nor expands on setup, which prevents adding unknown tri- axial loads to the sample. The coal to be encased in gypsum usu- ally must be trimmed with a wire saw to fit in one of the forms. Those samples immersed in water are not trimmed for the form until they are ready to be used. When a coal sample is going to be used for cutting tests, one face of the gypsum block is cut off about 1 in back, and the block is turned 90° and sawed lengthwise down the center. The coal is then held 23 in a gypsum block with flat sides and ends for rigid mounting in the test fix- ture, but the top and front face are open for test cuts at the proper bedding ori- entation. The coal samples are usually not cut open until the day before test- ing. New raw coal is obtained about ev- ery 6 months. SYNTHETIC SAMPLES To perform full-scale cutting tests in the laboratory , large coal samples would be required. It is not practical to ob- tain such samples since they tend to break during acquisition or transport. Also their acquisition disrupts mine operation. Large samples also tend to deteriorate rapidly in the laboratory. Simulated coal avoids all of these diffi- culties. It is made in blocks shaped to fit the test facility. Unlike coal, they have a uniform matrix, which allows for consistent testing. The best simulation material found to date is a modified gyp- sum or plaster mix. The physical characteristics of simu- lated coal are wide ranging, so the mate- rial can be tailored for specific charac- teristics. The strength can be varied by varying the mix. By reducing the mixing water, the brittleness of coal is ap- proached, whereas increasing water lowers strength and reduces brittleness. Major cleating in the sample is a third coal characteristic; however, this is very difficult to reproduce and is not yet fully refined. When mixing and pouring any simulated material, great care must be used in fol- lowing the recipe. Since little water is used, the plaster must have retarders and water reducers in the proper proportions to allow a complete and easy pour before the material sets up. Following this, the sample must be dried for about a month at 104° to 120° F to drive out all excess water and to obtain the desired brittleness . EXPERIMENTAL DESIGN The variability of coal and rock sam- ples used in cutting tests places severe restrictions on the design of the experi- ments. A standard bit (a plumb bob with a 60° included-angle carbide tip) is al- ways included in each experiment for di- rect comparative reference. Owing to the extremely variable nature of the test ma- terials, experimental results are treated as relative rather than absolute values. The size limitations of the sample blocks preclude performing an entire ex- periment on a single one. Since the blocks' responses vary, sometimes sub- stantially, the experimental design must incorporate the block differences. Block confounding and incomplete block designs are the most common methods used at TCRC to eliminate these effects. Hicks (_5 ) , Peng (8_) , and Davies (2^) provide back- ground for these and other methods. These methods do restrict the choice and range of variables that can be selected. In block confounding, the independent variables (e.g., cut depth, attack angle, bit type) must all have the same number of levels, i.e., there must be equal depths, angles, and types. With incom- plete block designs, only one independent variable can be tested in an experiment. An example is found in the experimental design for the asymmetric wear study (10). SUMMARY The Bureau of Mines cutting technology facility at TCRC has the equipment for a broad range of mineral fragmentation re- search with mechanical cutting tools. The equipment permits research from the fundamental aspects of cutter geometry and primary dust generation to the ap- plied studies of bit rotation, optimum depth of cut, and spacing. The facility is constantly changing to meet new re- search challenges, so the material de- scribed in this publication represents only the present situation. TCRC works closely on cooperative programs with in- dustry, and equipment is often modifiea to meet specific needs. 24 REFERENCES 1. Black, S., B. V. Johnson, R. L. Schmidt, and B. Banerjee. Effect of Con- tinuous Miner Parameters on the Genera- tion of Respirable Dust. Pres. at AMC Min. Conv. , San Fransisco, CA, Sept. 11- 14, 1977, and NCA/BCR Coal Conf . and Expo IV, Louisville, KY, Oct. 18-20, 1977; pub. in Min. Cong. J., v. 64, No. 4, Apr. 1978, pp. 19-25. 2. Davies , 0. L. The Design and Analysis of Industrial Experiments. Haf- ner, New York, 1960, 636 pp. 3. Hanson, B. D. Cutting Parameters Affecting Ignition Potential for Coni- cal Bits. BuMines RI 8820, 1983. Primary Dust Generation. 8761, 1983, 16 pp. BuMines RI 11. Roepke, W. W. , and B. D. Hanson. New Cutting Concepts for Continuous Miners. Coal Min. & Process., v. 16, No. 10, Oct. 1979, pp. 62-67. 12. Testing Modified Coal Cut- ting Bit Designs for Reduced Energy, Dust, and Incendivity. BuMines RI 8801, 1983. 13. Roepke, W. W. , B. D. Hanson, and C. E. Longfellow. Drag Bit Cutting Char- acteristics Using Sintered Diamond In- serts. BuMines RI 8802, 1983. 4. Hanson, B. D. , and W. W. Roepke. Effect of Symmetric Bit Wear and Attack Angle on Airborne Respirable Dust and En- ergy Consumption. BuMines RI 8395, 1979, 24 pp. 5. Hicks, C. R. Fundamental Concepts in the Design of Experiments. Rinehank & Winston, New York, 1964, 293 pp. 6. Johnson, B. V., S. W. Krepela, and K. C. Strebig. Field Testing the Microminer — Research Continuous Miner. BuMines TPR 89, 1975, 11 pp. 7. Larson, D. A., V. W. Dellorfano, C. F. Wingquist, and W. W. Roepke. Pre- liminary Evaluation of Bit Impact Ignition of Methane Using A Drum-Type Cutting Head. BuMines RI 8755, 1983, 23 pp. 8. Peng, K. C. The Design and Analy- sis of Scientific Experiments. Addison- Wesley, Reading, MA, 1967, 252 pp. 9. Roepke, W. W. , and S. J. Anderson (assigned to U.S. Dept. of the Interior). Triangular Shaped Cutting Head for Use With a Longwall Mining Machine. U.S. Pat. 4,303,277, Dec. 1, 1981. 10. Roepke, W. W. , and B. D. Hanson. Effect of Asymmetric Wear of Point At- :ack Bits on Coal-Cutting Parameters and 14. Roepke, W. W. , D. P. Lindroth, and T. A. Myren. Reduction of Dust and Ener- gy During Coal Cutting Using Point-Attack Bits. With An Analysis of Rotary Cutting and Development of a New Cutting Concept. BuMines RI 8185, 1976, 53 pp. 15. Roepke, W. W. , D. P. Lindroth, and J. W. Rasmussen (assigned to U.S. Dept. of the Interior) . Linear Cutting Rotary Head Continuous Mining Machine. U.S. Pat. 4,012,077, Mar. 15, 1977. 16. Roepke, W. W. , D. P. Lindroth, and R. J. Wilson (assigned to U.S. Dept. of the Interior). Transfer by Automatic Face Linear Cutting Rotary Head. U.S. Pat. 4,062,595, Dec. 13, 1977. 17. Roepke, W. W. , K. C. Strebig, and B. V. Johnson (assigned to U.S. Dept. of the Interior) . Method of Operating A Constant Depth Linear Cutting Head on a Retrofitted Continuous Mining Machine. U.S. Pat. 4,025,116, May 24, 1977. 18. Roepke, W. W. , and J. I. Voltz. Coal Cutting Forces and Primary Dust Generation Using Radial Gage Cutters. BuMines RI 8800, 1983. 19. Strebig, K. C, and H. W. Zeller. The Effect of Depth of Cut and Bit Type on the Generation of Respirable Dust. BuMines RI 8042, 1975, 16 pp. 25 APPENDIX. —SPECIFICATIONS OF MAJOR COMMERCIALLY AVAILABLE TEST EQUIPMENT COMPONENTS Small Linear Cutting Test System Table working surface 30 by 40 in (76.2 by 101.6 cm). Traverse range 24 in (60.96 cm). Rate range per minute 0.6 to 24 in (1.42 to 60.96 cm). Rate steps available 16. Maximum cutting force 4,000 lb (17.8 kN) . Maximum depth of cut 1-1/2 in (3.81 cm). Main drive motor 7-1/2 hp (3.81 cm). Net weight 5,050 lb (2,293 kg). Large Linear Cutting Test System Table working surface 40 by 128 in (101.6 by 325.1 cm). Traverse range 118 in (299.7 cm). Rate range per minute 1-15/16 to 62 in (4.92 to 157.48 cm). Rate steps available 16. Maximum cutting force Over 6,000 lb. Maximum depth of cut 4 in (10.16 cm). Main drive motor 10 hp. Net weight 97,000 lb (44,038 kg). Vertical Slotter Test System Ram (cutter) stroke range 3 to 22 in (7.62 to 55.88 cm). Cutter speed range 25 to 100 ft/min (0.76 to 3.05 m/min) Table diameter 28 in (71.1 cm). Table to lower face of ram (maximum) 44-1/2 in (113 cm). Table traverse — crossfeed distance (maximum). 24 in (60.96 cm). Table traverse — longitudinal distance (maximum) 32 in (81.28 cm). 26 Ram angular forward adjustment 0° to 10° C. System has an automatic rotary table capability. Maximum rated cutting force at slow speed.... 11,000 lb (48.9 kN) . Main drive motor 10 hp. Net weight 14,200 lb (6,447 kg). Three-Axis Dynamometer for Large Linear Cutting System Horizontal (tangential) and normal cutting forces— FZ, FY (maximum) 18,000 lb (80 kN) . Lateral force — FX (maximum) 2,000 lb (8.89 kN) . Crosstalk Less than 5 pet. £U.S. GOVERNMENT PRINTING OFFICE: 1983-605-015/62 INT.-BU.OF MINES, PGH..P A. 27057 ©406 0^ o°..l a ♦_ *C .o^*. V .4> ,r^. ^ .4T **>^'. V «° /^tfV. °- 4^ .♦>^% " LIBRARY OF CONGRESS 002 959 913 I