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 Bureau of Mines Information Circular/1987 
 
 Surface Testing and Evaluation 
 of the Monorail Bridge Conveyor 
 System 
 
 By Robert J. Evans, William D. Mayercheck, 
 and Joseph L. Saliunas 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
Information Circular 9146 
 
 Surface Testing and Evaluation 
 of the Monorail Bridge Conveyor 
 System 
 
 By Robert J. Evans, William D. Mayercheck, 
 and Joseph L. Saliunas 
 
 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: 
 
 
 Evans, Robert J. 
 
 Surface testing and evaluation of the monorail bridge conveyor 
 system. 
 
 (Information circular ; 9146) 
 
 Bibliography. 
 
 Supt. of Docs, no.: 1 28.27: 9146. 
 
 1. Mining machinery -Testing. 2. Monorail conveyors -Testing. 1. Mayercheck. William L). 
 II. Saliunas, Joseph L. III. Title. IV. Series: Information circular (United States. Bureau of 
 Mines) ; 9146. 
 
 TN295.U4 [TN345] 
 
 622 s 
 
 [622'.66] 
 
 86-600401 
 
CONTENTS 
 
 Page 
 
 Abstract 
 
 Introduction 
 
 Background 
 
 Description of monorail bridge conveyor system 3 
 
 Conveyor units • • 
 
 Power and control 5 
 
 Tramming and support system 8 
 
 Inby support 9 
 
 Outby support 9 
 
 Surface testing 10 
 
 Test rig installation 10 
 
 Initial checkout 11 
 
 Power consumption 12 
 
 Disabled brake test 14 
 
 Haulage rate 14 
 
 Miner loading trials 16 
 
 Reliability 17 
 
 System compatibility with low-belt structure 20 
 
 Suspension of monorail track by chain hangers 20 
 
 System compatibility with hopper-feeder 22 
 
 Summary of surface test findings 22 
 
 Modifications 22 
 
 Mining plans 24 
 
 Conclusions 31 
 
 Appendix A. — Modifications to the monorail bridge conveyor system 32 
 
 ILLUSTRATIONS 
 
 1. Three types of monorail bridge conveyor units 3 
 
 2. Plan view of monorail bridge conveyor unit 5 
 
 3. Intermediate unit 6 
 
 4. Inby unit 6 
 
 5. Outby control boxes 7 
 
 6. Pendant control 7 
 
 7. Monorail T-section track configurations 8 
 
 8. Monorail hardware 9 
 
 9. Outby support with dolly 10 
 
 10. Surface test rig 11 
 
 11. Monorail bridge conveyor system in test rig 11 
 
 12. Typical power-consumption plots 14 
 
 13. Closed-loop configuration 14 
 
 14. Monorail bridge conveyor units at maximum-angle relationship 15 
 
 15. Haulage-rate plot 16 
 
 16. Haulage-rate and power plots during maximum haulage-rate trial 16 
 
 17. Continuous miner loading directly into monorail bridge conveyor 17 
 
 18. Loading rate and power consumption during reliability trial 18 
 
 19. Spillage under inby monorail bridge conveyor transfer point 19 
 
 20. Profile of chain-suspended monorail track 21 
 
 21. Chain hanger 21 
 
 22. Hopper-feeder-bolter 23 
 
 23. Hopper-feeder-bolter compatibility trial 23 
 
11 
 
 ILLUSTRATIONS— Continued 
 
 Page 
 
 24. 
 25. 
 26. 
 27, 
 28. 
 29. 
 30. 
 31. 
 32, 
 33. 
 34. 
 35. 
 36. 
 
 Monorail installation with chain hangers , 
 
 Monorail installation with roof plates over low-belt structure. 
 
 Monorail bridge conveyor track turnout plans , 
 
 Five-entry mine plan 
 
 Five-entry 60° mine plan with rooms , 
 
 Seven-entry mine plan , 
 
 Mine plan for longwall panel-entry development , 
 
 Monorail bridge conveyor used with shortwall mining system...., 
 
 Monorail bridge conveyor with continuous miner , 
 
 Hopper-feeder-bolter , 
 
 Monorail bridge conveyor used with hopper-feeder , 
 
 Monorail bridge conveyor-hopper-feeder interface , 
 
 Monorail track, installation plan , 
 
 TABLES 
 
 Monorail bridge conveyor specifications , 
 
 Monorail bridge conveyor power consumption , 
 
 24 
 25 
 25 
 26 
 27 
 27 
 28 
 28 
 29 
 29 
 30 
 30 
 31 
 
 4 
 13 
 
 
 UNIT OF MEASURE 
 
 ABBREVIATIONS USED 
 
 IN THIS REPORT 
 
 ft 
 
 foot 
 
 lb/ft 
 
 pound per foot 
 
 ff lb 
 
 foot pound 
 
 min 
 
 minute 
 
 ft/min 
 
 foot per minute 
 
 pet 
 
 percent 
 
 h 
 
 hour 
 
 r/min 
 
 revolution per minute 
 
 hp 
 
 horsepower 
 
 s 
 
 second 
 
 Hz 
 
 hertz 
 
 St 
 
 short ton 
 
 in 
 
 inch 
 
 st/h 
 
 short ton per hour 
 
 in/ft 
 
 inch per foot 
 
 V ac 
 
 volt, alternating current 
 
 kW 
 
 kilowatt 
 
 V dc 
 
 volt, direct current 
 
 lb 
 
 pound 
 
 W 
 
 watt 
 
SURFACE TESTING AND EVALUATION OF THE MONORAIL BRIDGE 
 
 CONVEYOR SYSTEM 
 
 By Robert J. Evans, 1 William D. Mayercheck, 2 and Joseph L. Saliunas 3 
 
 ABSTRACT 
 
 The monorail bridge conveyor (MBC) is a prototype continuous face 
 haulage system that was surface tested and evaluated by the Bureau of 
 Mines. The MBC consists of a series of cascading belt bridge conveyors 
 suspended from roof-supported monorail track. Tests were conducted to 
 determine MBC haulage capability, maneuverability, power consumption, 
 and reliability using rigid and chain-suspended monorail track installa- 
 tions. Subsequent modifications to improve operation and reliability 
 made during surface testing are described. Mining plans were devised 
 to show potential MBC installations for room-and-pillar, longwall devel- 
 opment, and shortwall mining sections. Compatibility tests were con- 
 ducted with the Bureau's prototype hopper-feeder, to provide additional 
 surge capacity and lump-breaking capability. Results from the surface 
 test program, along with modifications to improve system operation and 
 reliability, indicate that the MBC has the potential to perform success- 
 fully in an in-mine trial. 
 
 'Civil engineer, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
 Supervisory physical scientist, Pittsburgh Research Center. 
 3 Project engineer, Boeing Services International, Pittsburgh, PA. 
 
INTRODUCTION 
 
 The Bureau of Mines has sponsored nu- 
 merous high-risk research programs over 
 the past decade to improve productivity 
 and health and safety in underground coal 
 raining by advancing state-of-the-art con- 
 tinuous face haulage systems. These sys- 
 tems are designed to move coal nonstop 
 from the continuous miner to the next 
 stage of rail or belt haulage (approxi- 
 mately 500 ft). One of the more innova- 
 tive continuous face haulage systems is 
 the monorail bridge conveyor (MBC). The 
 MBC consists of a series of cascading 
 belt conveyors supported by an inverted 
 T-section monorail bolted to the mine 
 roof. The basic concept was conceived 
 and patented by the Bureau in 1979 (U.S. 
 Pat. 4,157,757). It was designed and 
 fabricated by the Goodman Conveyor Co. , 
 Inc. under a cost-sharing arrangement 
 
 with the Bureau (contract J0333917). 
 This system has the potential to improve 
 productivity over conventional shuttle- 
 car haulage systems by eliminating 
 shuttle-car change, which can amount to 
 10 pet of the total face time for a con- 
 tinuous miner per shift; it provides a 
 captive guidance system that requires 
 only one operator, regardless of length; 
 and it allows haulage in poor bottom con- 
 ditions where conventional rubber tired 
 and cat systems could not operate effi- 
 ciently. Two of the MBC safety features 
 are elimination of potential shuttle-car 
 trailing cable and moving-vehicle acci- 
 dents. MBC applications include all 
 room-and-pillar operations such as driv- 
 ing rooms, entries and panels, pillar ex- 
 traction, and shortwall mining. 
 
 BACKGROUND 
 
 Underground continuous haulage systems 
 have been employed in Europe and the 
 United States since 1970. Commercially 
 available systems can be grouped into 
 three general categories: (1) crawler- 
 mounted alternating series of mobile 
 bridge carriers and piggyback bridge con- 
 veyors, and (2) monorail suspended sys- 
 tems, and (3) noncascading systems. The 
 crawler-mounted systems generally require 
 an operator every 50 ft and are limited 
 to a total length of under 200 ft. 
 
 The only commercial monorail system 
 available today has been installed in a 
 U.S. trona mine and at several foreign 
 locations. Although it has a unique con- 
 tinuous belt with no crossover points, it 
 is relatively heavier and more expensive, 
 and it is more difficult to change the 
 system length in comparison with the MBC 
 system, which can attain a length of more 
 than 500 ft with just a single operator. 
 
 The noncascading systems, which have 
 been recently introduced and remain un- 
 tested underground, are relatively more 
 expensive and present more difficulties 
 in changing the system length. 
 
 Extensive surface testing and evalu- 
 ation of the MBC was conducted by the 
 Bureau. The objectives of the surface 
 test and evaluation program were to — 
 
 1. Rigorously test the MBC and improve 
 performance, based upon observations made 
 under simulated underground operation; 
 
 2. Measure MBC performance criteria so 
 that underground performance and operat- 
 ing requirements could be predicted; 
 
 3. Determine if the MBC meets its de- 
 sign criteria and is worthy of an in-mine 
 trial; and 
 
 4. Prepare the MBC for an in-mine 
 trial including electrical approval by 
 the Mine Safety and Health Administration 
 (MSHA). 
 
 The principal advantages of surface 
 testing, prior to an in-mine trial, are 
 that equipment performance can be proven, 
 and improved upon, without interfering 
 with production at an operating mine. 
 This is absolutely paramount with face 
 equipment such as the MBC. Even though 
 the MBC has several potential advantages, 
 most mines would not risk the instal- 
 lation and operation of unproven face 
 equipment, since any failure would result 
 in higher operating costs and lost pro- 
 duction. Therefore, the raining industry 
 tends to resist the introduction of novel 
 raining systems if the in-mine trial does 
 not meet anticipated short-term results. 
 Even though the most rigorous surface 
 
test and evaluation program will not sub- 
 ject equipment to all of the harsh condi- 
 tions found in underground mines, a sur- 
 face test program does significantly 
 increase the probability that the initial 
 underground trial will be successful. 
 
 Surface testing of the MBC commenced in 
 September 1982 and final modifications to 
 prepare the MBC for in-mine use were com- 
 pleted in August 1985. 
 
 DESCRIPTION OF MONORAIL BRIDGE CONVEYOR SYSTEM 
 
 The MBC consists of a series of cascad- 
 ing belt conveyors suspended from special 
 roof-supported monorail. The MBC-systera 
 specifications are shown in table 1. 
 
 The three types of MBC units (inby, 
 intermediate, and outby) are shown in 
 figure 1. Each unit consists of a belt 
 conveyor mounted on a rigid frame, mono- 
 rail-suspension hardware, a monorail- 
 mounted tram unit, and electric power and 
 control components. All MBC units are 
 totally monorail suspended except for the 
 inby and outby units. The inby end of 
 the inby unit is mounted on rubber tires, 
 which are steered remotely. The outby 
 end of the outby unit can be supported 
 
 either by a dolly mounted on a rigid-belt 
 structure or by monorail directly over 
 the section belt. See table 1 for de- 
 scriptions of various MBC components (in- 
 cluding modifications made during the 
 test program). 
 
 CONVEYOR UNITS 
 
 Individual conveyor units are fabri- 
 cated from hollow structural tubing, pro- 
 viding a lightweight and rigid frame. 
 Conveyor units are 27 ft, 7 in long over- 
 all, with an active length of 24 ft. 
 Presently, 12 conveyor units are avail- 
 able for a system length of 288 ft; 
 
 wm/m/Mmmm/mmm//mMW//mf//m/m///im//m 
 
 j ggjrts^fe-— ^&^^^4&^ m^ 
 
 Inby unit 
 
 - — --■ T T --" 
 
 Intermediate unit 
 
 
 Outby unit 
 
 FIGURE 1.— Three types of monorail bridge conveyor units. 
 
TABLE 1. - Monorail bridge conveyor specifications 
 
 (Prototype system: 12 conveyor units available for 288-ft length; 
 expandable to greater length) 
 
 .1.2 
 
 System specifications 
 
 Haulage rate, nominal st/h.. 600 
 
 Tram speed, constant ft/min. . 60 
 
 Electric power requirements, V ac: 
 
 Main system 460 
 
 Control system 120 
 
 Power output, total (for 12 units), hp: 
 
 Conveying 120 
 
 Tramming 20 
 
 Entry width, recommended minimum f t. . 14 
 
 Load, typical maximum on a suspension point lb.. 2,000 
 
 Working height, minimum, in: 
 
 Without low-belt structure 48 
 
 With low-belt structure 54 
 
 Gradability, recommended maximum pet.. 6.5 
 
 Curved-track radius f t. . 24 
 
 Crosscut geometry 3 °. . 60-90 
 
 Individual bridge specifications: 
 Dimensions, ft: 
 Length: 
 
 Overall 27.6 
 
 Active 24 
 
 Width, overall 
 
 Carrier idlers (on 25° angle), diameter in.. 4 
 
 Rollers, head and tail, diameter in. . 
 
 Belt width in. . 36 
 
 Belt speed, constant ft/min. . 400 
 
 Power output, hp: 
 
 Tram drive motor 1.5 
 
 Conveyor motor 10 
 
 Weight (empty) lb. . 4, 200 
 
 Monorail track: 24-ft radius, designed for 60° crosscuts; available in 7- and 10- 
 ft lengths; weight, 7 lb/ft; suspended on 4-ft centers. 
 Inby support: remotely steered rubber tires. 
 
 3 90° crosscut: Compound curve must be used with the stipulation that intersecting 
 arc lengths must not exceed 30° to prevent interference. 
 
 NOTE. — All units can be controlled by single operator; helper optional. Safety 
 features: Belt slip and sequence switches, disk brakes on each tram unit that engage 
 automatically when tram power is shut off, emergency stop on each unit, pendant con- 
 trol from any unit, end-of-monorail stop on inby unit, and warning horn before belt 
 startup. 
 
however, with electrical modification, 
 additional units can be added to provide 
 increased system length. A plan view of 
 a typical intermediate unit is shown in 
 figure 2. A 36-in-wide, 5/16-in-thick 
 belt is supported on a conveyor unit with 
 a maximum width of 7 ft. Catenary-type, 
 4-in-diam carrier idlers are installed 
 on a 25° troughing angle. A 1,750-r/min, 
 10-hp electric motor powers the belt on 
 each unit. A 7:1 double-reduction gear- 
 speed reducer is coupled to the head- 
 drive roller to provide a constant 400- 
 ft/min belt speed, and 7-in-diam crowned 
 drive and idler rollers are used. The 
 tail idler roller is mounted on an ad- 
 justable screw-type takeup. The belt has 
 a rated capacity of 600 st/h. Compres- 
 sion-spring belt cleaners are mounted 
 under the head roller of each unit. 
 
 POWER AND CONTROL 
 
 The MBC is operated by 460-V ac, three- 
 phase, 60-Hz electric power provided by a 
 No. 2/0 trailing cable to the outby main 
 breaker box. Transformers located in 
 
 each motor control box supply 120-V ac, 
 single-phase, 60-Hz power for the control 
 system. The 10-hp, 440-V ac, single- 
 speed conveyor motors and the 1-1/2-hp, 
 440-V ac, single-speed, reversing tram 
 motors have across-the-line starting. 
 The motor control box on each unit is 
 equipped with an emergency-stop pushbut- 
 ton station that disengages the main cir- 
 cuit breaker. 
 
 The electrical system is modular in de- 
 sign with identical power and control 
 wiring on all but the inby and outby 
 units. Figure 3 shows a typical interme- 
 diate unit containing the motor control 
 case and interconnecting cables common 
 to all units. The inby unit has an addi- 
 tional control case (fig. 4) that is 
 required for the steering motor and head- 
 light controls. The outby unit is con- 
 nected to two additional control cases 
 (fig. 5): the main breaker case, which 
 houses the main-system circuit breaker, 
 and the master control case, which con- 
 tains the emergency-stop controls for the 
 entire system. 
 
 Tail roller 
 
 Belt sequence switch 
 
 switch Motor control case 
 
 J i Head roller 
 
 Belt takeup mechanism Troughing idler 
 
 \ 
 
 Coupler 
 
 IO-hp electric motor 
 
 Gear-speed reducer 
 
 •*- Inby 
 
 Note: Belting not shown 
 
 Outby 
 
 FIGURE 2.— Plan view of monorail bridge conveyor unit. 
 

 
 FIGURE 3.— Intermediate unit. 
 
 FIGURE 4.— Inby unit. 
 
FIGURE 5.— Outby control boxes. 
 
 FIGURE 6.— Pendant control. 
 
The MBC system employs automatic se- 
 quential belt startup. When the conveyor 
 is first activated, an audible warning 
 signal is heard. After a brief period 
 che signal stops, and the conveyors start 
 in sequence beginning with the outby 
 unit. Sequence switches allow each suc- 
 cessive unit to start only after the pre- 
 ceding unit is running at full speed. 
 Should a conveyor stop for any reason, 
 all conveyors inby the defective unit 
 will stop automatically. Each unit has a 
 manual ovverride that will operate the 
 conveyor on that unit. This control is 
 intended for maintenance and diagnostic 
 use only. 
 
 Controls for steering, tramming, and 
 conveying are located on an umbilical 
 pendant control. The pendant control 
 (fig. 6) may be connected to any unit in 
 the system. This provides operator con- 
 venience and allows positioning to avoid 
 blind or unsafe MBC operation locations. 
 During face operations, the pendant con- 
 trol will typically be located on the 
 inby unit, so the operator can best con- 
 trol the inby steering. 
 
 The MBC system can be trammed on the 
 monorail track in both the inby and outby 
 directions, with each tram motor equipped 
 with an electric brake. The brake re- 
 mains set when the machine is stationary. 
 Upon activation of the tram control, the 
 brake releases and sets again when the 
 tram control is deactivated. If a brake 
 becomes overheated, it can be manually 
 released to prevent further heat buildup. 
 
 Should any unit develop a major mal- 
 function requiring it to be removed from 
 the system, all electrical connections 
 can be disconnected at the plugs and re- 
 ceptacles that interconnect the units. 
 The units are reconnected in the same 
 manner. 
 
 TRAMMING AND SUPPORT SYSTEM 
 
 Both ends of each conveyor unit are 
 supported by eight-wheeL carrier assem- 
 blies that distribute the weight of 
 each conveyor on the monorail track. 
 The carriers are designed to follow both 
 vertical and horizontal curves in mono- 
 rail track without affecting conveyor 
 suspension. A 1,100-r/min, 440-V ac, 
 
 1.5-hp traction motor is used for 
 tramming each conveyor unit. The motor 
 drives two rubber wheels that are held 
 against the underside of the monorail 
 track. A 24:1 triple-reduction speed re- 
 ducer is used to provide a constant tram- 
 ming speed of 60 ft/min. Disk brakes on 
 each tram motor automatically engage when 
 the system is not being trammed. 
 
 Lightweight monorail track is used to 
 suspend the MBC system. The inverted 
 T-section track, made by Cleveland Tram- 
 rail (Cleveland Crane and Engineering, 
 Div. of McNeil Corp., Wickliffe, OH) 4 
 weighs 7 lb/ft and comes in eight fac- 
 tory-available configurations, as illus- 
 trated in figure 7. Straight rail is 
 available in 14-, 10-, and 7-ft lengths. 
 Curved and combination rails in vari- 
 ous lengths make 60° turnouts with a 24- 
 ft radius. Other lengths and config- 
 urations of monorail can be fabricated 
 underground to suit particular mine con- 
 ditions. A hydraulic rail bender is com- 
 mercially available for field-fitting 
 curves. Four bolts are used to join 
 
 ^Reference to specific products does 
 not imply endorsement by the Bureau of 
 Mines. 
 
 14' 
 
 , u 
 
 LH switch 
 
 10' 
 
 I 
 
 r 
 
 7' 
 
 L 
 
 MK-I MK-2 NIK-6 MK-3 MK-5 MK-4 
 
 straight straight straight curved curved curved 
 
 Note: All curves on 
 24-ft radius 
 
 FIGURE 7.— Monorail T-section track configurations with 
 designated identification numbers. 
 
monorail track at overlapping splice 
 plates. Both right- and left-hand man- 
 ually operated monorail switches are 
 available. Figure 8 shows two types of 
 hardware that can be used to suspend 
 monorail track. One type of suspension 
 hardware uses a semirigid connection to 
 suspend monorail track from roof plates 
 attached to the mine roof with two roof 
 bolts. Bevel-headed bolts seated in the 
 roof plates are connected to the monorail 
 track, allowing limited horizontal track 
 movement. A second type of suspension 
 hardware enables a nonrigid connection to 
 suspend the monorail track using a chain- 
 hanger bracket attached to the mine roof 
 with one roof bolt. Varying lengths of 
 chain connect the monorail track to the 
 chain-hanger bracket, allowing horizontal 
 and vertical movement of the monorail 
 track. 
 
 INBY SUPPORT 
 
 The inby end of the MBC system is sup- 
 ported by two 9-in-wide rubber tires 
 
 installed on 38-in centers. The wheels 
 are powered by a 1.5-hp electric motor 
 at 60-ft/min constant tram speed. The 
 tram motor and gear-speed reducer are 
 mounted behind the rubber wheels. A sep- 
 arate 440-V ac, 1.5-hp electric motor and 
 ball thread are used to steer the inby 
 wheel carriage. The steering motor is 
 controlled from the pendant control. 
 
 The height of the inby conveyor unit 
 over the rubber tires is 32 in. The 
 height was increased to 40 in with the 
 addition of a low-profile hopper. 
 
 OUTBY SUPPORT 
 
 In low-coal applications, the monorail 
 track can be offset from the panel belt, 
 and the outby end of the MBC can be sup- 
 ported by a dolly mounted on rigid belt 
 structure (fig. 9) or on a chain panline. 
 The dolly ensures transfer onto the panel 
 belt without spillage. In higher coal, 
 the outby end of the MBC could be sus- 
 pended from monorail installed directly 
 over the panel belt. 
 
 Chain-hanger assembly 
 
 Roof plat© 
 
 FIGURE 8.— Monorail hardware. 
 
10 
 
 FIGURE 9.— Outby support with dolly. 
 
 SURFACE TESTING 
 
 Surface tests were conducted to verify 
 and measure MBC haulage capability, ma- 
 neuverability, power consumption, and re- 
 liability. Both rigid- and chain-sus- 
 pended monorail track installations were 
 evaluated. Numerous modifications were 
 made to several MBC subsystems to correct 
 deficiencies noted during surface test- 
 ing. Important test sequences were re- 
 corded on videotape and are available at 
 the Pittsburgh Research Center. 
 
 TEST RIG INSTALLATION 
 
 A steel structure was constructed at 
 the test facility to support the MBC dur- 
 ing surface testing. This test rig (fig. 
 10) functioned as a false mine roof and 
 was required to suspend the monorail 
 track. The test rig enabled MBC testing 
 on straight and radius tracks, through 
 switches, and on a 6-1/2-pct grade. It 
 consisted of nine arches that supported 
 underhung beams. Two separate 140-ft 
 lengths of monorail track were supported 
 
 from the underhung beams. The two mono- 
 rail track sections were parallel to each 
 other and offset by 8 ft. Two 80-ft por- 
 tions of both monorail tracks were in- 
 stalled on a 6-1/2-pct slope. A single, 
 60-ft arc length of the 24-ft-radius 
 monorail track was connected to the main 
 track by a switch. This basic test rig 
 was used to support both rigidly bolted 
 and chain-suspended monorail tracks. For 
 initial test sequences, the monorail 
 track was bolted to roof plates that were 
 rigidly bolted to the underhung beams. 
 
 A 140 ft length of auxiliary belt 
 structure was installed under one of the 
 monorail tracks. The belt structure sup- 
 ported a 48-in-wide conventional belt 
 that operated at 625 ft/min and was pow- 
 ered by a 50-hp electric motor. This 
 auxiliary belt was used during closed- 
 loop coal conveying tests. A beltscale 
 weigh bridge was installed in this auxil- 
 iary belt to measure the MBC haulage 
 rate. 
 
11 
 
 Offset track t _ 
 Main track <L "* 
 
 PLAN VIEW 
 
 Belt-scale weigh bridge 
 
 48 -in auxiliary belt 
 
 £3— 
 
 Switch ^ s 
 
 Radius track 
 
 6 72-pct grade 
 
 Level 
 
 SIDE VIEW 
 
 FIGURE 10.— Surface test rig. 
 
 48- in auxiliary belt 
 
 FIGURE 11.— Monorail bridge conveyor system in test rig. 
 
 Although the MBC consists of 12 con- 
 veyor units, only the three (3) unique 
 units (inby, intermediate, and outby) 
 were used for surface testing because all 
 potential MBC configurations could be 
 represented using these three units. 
 
 The MBC was installed into the test 
 rig using a chain hoist, forklift, and 
 mobile crane. First, the eight-wheel 
 carrier components were lifted by hand 
 and threaded onto an open end of monorail 
 track. Next, the tram units and suspen- 
 sion frames were moved into position, 
 aided by a 1-1/2-st chain hoist. Con- 
 veyor units were then moved under the 
 suspension frames by forklift and picked 
 up by the mobile crane and pinned to the 
 suspension frame. Figure 11 shows the 
 MBC units installed in the test rig. For 
 initial test sequences, the outby end 
 of the outby carrier was installed on 
 the offset monorail track over the auxil- 
 iary belt, and the remaining carriers 
 were installed on the main track. No 
 
 difficulties were encountered during in- 
 stallation of the MBC units into the 
 test rig. Although equipment that would 
 not be available underground was used, a 
 roof-mounted chain hoist and a scoop car 
 could perform the same functions as the 
 crane and forklift. After the conveyors 
 were suspended, power and control cables 
 were installed, and proper tram and 
 conveyor-motor electrical operation was 
 verified. Tram drive wheels were then 
 adjusted to proper tension against the 
 bottom of the monorail track, conveyor 
 belts were adjusted to track in the cen- 
 ter of the idlers, and test personnel 
 were trained in proper operation. 
 
 INITIAL CHECKOUT 
 
 After proper MBC operation was veri- 
 fied, preliminary tramming and conveyor 
 function tests were performed. The MBC 
 was trammed through the test rig and into 
 the switch several times. The system was 
 
12 
 
 able to tram upgrade, downgrade, and 
 through the switch without difficulty. 
 Several modifications were necessary be- 
 fore coal handling was possible. The 
 power and control cables were shortened 
 to proper lengths, because excess weight 
 had caused the units to lean toward the 
 cables. Spillage guards were added on 
 all dump points. (Appendix A lists all 
 modifications made during the test pro- 
 gram. ) After the modifications were com- 
 pleted, preliminary loading trials were 
 conducted with all MBC units in straight 
 alignment. The MBC was intermittently 
 loaded into the inby MBC hopper by a slow 
 discharge of coal from the 500-lb capac- 
 ity bucket of a skid loader. It was then 
 loaded for several minutes by an 8-st- 
 capacity shuttle car dumping into the 
 inby MBC hopper. No major operational 
 problems were encountered with the MBC 
 during these tests, and it was able to 
 convey coal at normal haulage rates. 
 
 During the initial checkout, a deci- 
 sion was made to install an automatic 
 steering control for the inby rubber 
 wheels. The original manual steering 
 wheel, located beside the inby hopper, 
 was awkward to operate and potentially 
 unsafe. New gearing, a mounting bracket, 
 an electric motor, and a control switch 
 were installed. 
 
 POWER CONSUMPTION 
 
 Power-consumption trials were conducted 
 to determine overall system electrical 
 characteristics and to specifically in- 
 vestigate if the number of tram motors 
 could be decreased without affecting 
 system performance. Each MBC unit is 
 equipped with one monorail tram drive. 
 An additional rubber-wheel tram drive is 
 used on the inby unit. The rubber- 
 wheeled tram drive on the inby unit, lo- 
 cated several inches off the ground, was 
 determined to be in an undesirable loca- 
 tion because of potential water damage 
 and ground clearance problems. There- 
 fore, it was desirable to eliminate this 
 motor, but only if doing so would not 
 overload the remaining motors. For the 
 power-consumption trials, the number and 
 location of the tram motors were varied 
 for both loaded and unloaded conveyors, 
 
 and for upgrade and downgrade gradients. 
 The test variables and results of these 
 trials are listed in table 2. 
 
 The power consumption of the MBC tram 
 motors was monitored by utilizing a cur- 
 rent transformer with a ratio of 150:5 on 
 the A and C phase legs of the MBC power 
 cable. The current transformers were 
 connected to transducers, which provided 
 a 0- to 10-V dc output for a 0- to 120-kW 
 power span. The current transformers had 
 a factory-stated accuracy of ±1 pet. The 
 watt transducers had a stated accuracy of 
 ±0.25 pet. All power-consumption data 
 were recorded by an eight-channel strip- 
 chart recorder. Channel calibration was 
 performed before each test. 
 
 For each test, the power-consumption 
 instrumentation and recorder were acti- 
 vated, and the MBC system was trammed 
 through predetermined start and stop 
 points. The floor area underneath the 
 inby unit was cleaned so that the rolling 
 resistance of the inby rubber wheel would 
 not vary. 
 
 For all trials (table 2) except G, H, 
 I, and J, the original roller chain drive 
 on the inby rubber wheels was connected. 
 (This original roller chain drive was 
 later replaced with a sealed, gear-speed- 
 reducer driver. ) For the trials using 
 three rail motors (E, F, G, H, I, and J), 
 the rubber-wheeled tram drive was elec- 
 trically disconnected. For the trials 
 using only two rail motors (S, T, V, W), 
 only the monorail tram drives on the inby 
 and outby units were operated, and the 
 inby rubber-wheeled tram drive and inter- 
 mediate unit monorail tram drive were 
 electrically disconnected. For the tri- 
 als using four rail motors (X, Y, Z, and 
 AA), an additional tram motor was in- 
 stalled on the monorail immediately outby 
 the inby unit tram motor. These two tram 
 motors were connected by a short drawbar. 
 
 For trials A through (table 2), the 
 average power consumption for both level 
 and 6-1/2-pct-grade track was determined. 
 The power consumption for a 20-ft length 
 of track, at the start of upgrade trials 
 and at the end of downgrade trials (fig. 
 11), was used for the level, kW on level 
 track column of table 2. The power 
 consumption for a 10-ft length of track, 
 at the end of the upgrade trials and at 
 
13 
 
 TABLE 2. 
 
 - Monorail 
 
 bridge 
 
 convey 
 
 or power 
 
 consumpt ion 
 
 
 Trial 
 
 
 Motors used 
 
 Level, 1 
 
 av kW 
 
 Grade, 
 av kW 
 
 Peak, 
 
 kW 
 
 Design, 
 
 
 Rail 
 
 Wheel 
 
 max kW 
 
 
 
 UPGRADE 
 
 GRADIENT 
 
 
 
 
 Conveyors 
 A 
 
 unloaded: 
 
 
 3 
 
 3 
 
 2 3 
 
 2 
 
 4 
 
 3 
 
 2 3 
 
 3 
 
 4 
 
 1 
 
 
 
 
 
 1 
 
 
 
 
 2.8 
 2.0 
 1.8 
 ( 3 ) 
 ( 3 ) 
 
 2.9 
 2.0 
 ( 3 ) 
 ( 3 ) 
 
 4.1 
 3.5 
 3.4 
 3.4 
 4.3 
 
 4.7 
 4.0 
 4.0 
 4.7 
 
 5.0 
 3.8 
 3.6 
 3.6 
 
 4.8 
 
 5.8 
 4.8 
 4.2 
 5.8 
 
 4.5 
 
 E 
 
 3.4 
 
 G 
 
 3.4 
 
 s 
 
 2.2 
 
 z r 
 
 4.5 
 
 Conveyors 
 
 
 loaded: 
 
 
 4.5 
 
 J 
 
 3.4 
 
 W 
 
 2.2 
 
 
 4.5 
 
 
 
 DOWNGRADE 
 
 GRADIENT 
 
 
 
 
 Conveyors 
 B 
 
 unloaded: 
 
 
 3 
 3 
 2 3 
 2 
 4 
 
 2 3 
 3 
 2 
 4 
 
 1 
 1 
 
 
 
 
 
 
 1 
 
 
 
 
 2.8 
 
 1.9 
 1.7 
 ( 3 ) 
 ( 2 ) 
 
 2.0 
 2.9 
 ( 3 ) 
 ( 3 ) 
 
 1.4 
 .7 
 .5 
 .5 
 
 1.3 
 
 .4 
 1.3 
 
 .4 
 1.1 
 
 3.4 
 2.2 
 1.8 
 2.3 
 2.9 
 
 2.2 
 3.1 
 3.1 
 3.1 
 
 4.5 
 
 F 
 
 3.4 
 
 H 
 
 3.4 
 
 T 
 
 2.2 
 
 AA 
 
 4.5 
 
 Conveyors 
 I 
 
 loaded: 
 
 
 3.4 
 
 N 
 
 4.5 
 
 V. . . 
 
 2.2 
 
 
 4.5 
 
 For "upgrade gradient," the units were traveling from right to left, and 
 for "downgrade gradient," the units were traveling from left to right on the 
 level portion of track. 
 
 Rubber-wheeled tram drive electrically and mechanically disconnected for 
 these trials. 
 
 Test configurations did not permit power readings on level track sections. 
 
 the beginning of the downgrade trials, 
 was used for the "Grade, av kW" (6-1/2- 
 pct) column of table 2. Between these 
 points, the grade traveled by each tram 
 motor varied. 
 
 The strip-chart data were visually 
 averaged for both the "level" and "grade" 
 kilowatt values. The "Peak, kW" column 
 of table 2 was taken as the maximum in- 
 stantaneous power draw recorded by the 
 strip chart for each trial (exclusive of 
 starting power). The "Design, max kW" 
 column of table 2 was obtained by multi- 
 plying the number of tram motors used and 
 the nameplate horsepower rating by the 
 conversion factor for horsepower and 
 kilowatt. 
 
 For trials S through AA, only the aver- 
 age and peak power consumptions for the 
 6-1/2-pct grade were determined, because 
 the test-rig configuration did not allow 
 
 the MBC system to tram on the entire lev- 
 el track section. 
 
 Figure 12 shows the strip-chart read- 
 outs from two typical trials. For trial 
 J, three rail motors were used on the 
 loaded MBC system, and the average power 
 consumption while tramming up the grade 
 was 18 pet over the design maximum power 
 draw. For trial 0, three rail motors and 
 the inby rubber-wheel tram drive were 
 connected, and the average power consump- 
 tion while tramming upgrade was 4 pet 
 over the design maximum power draw. For 
 both trials, power consumption while 
 tramming on the level was below the de- 
 sign maximum. These data indicate that 
 the inby rubber-wheel tram drive would be 
 removed if the system normally operates 
 on a level grade; however, tram-motor 
 life would be shortened if the system 
 must regularly tram upgrade. 
 
14 
 
 DISABLED BRAKE TEST 
 
 The objective of the disabled brake 
 test was to determine if the loaded MBC 
 system would safely hold while station- 
 ary on the 6-1/2-pct grade with a dis- 
 abled brake. The loaded MBC system was 
 trammed into the 6-1/2-pct grade rack 
 section, and the brake on the inby unit 
 was electrically deactivated. The sys- 
 tem remained stationary. Next, the inby 
 and intermediate unit brakes were 
 
 4 — 
 
 « i I I I I I I I I I I I I I I | I I I I I I | I I I I 
 Trial J 
 Loaded, upgrade 3rail motors 
 
 [Grade 
 
 • Level 
 
 -3.4-kWdesign,maximum 
 
 2 
 
 s |2 r 
 
 -Level 
 
 1 ' ' ' ' ' ' ' I ' ' 'tridlO » ' l i i I i i I. 
 Loaded upgrade 3 rail motor, I wheel motor ; 
 
 ^ /4.5-kW design, maximum 
 
 ~vAv v * 
 
 10 
 
 I I I I I 
 
 ■ I ■ 
 
 20 
 
 25 
 
 FIGURE 12.— Typical power-consumption plots. 
 
 deactivated, and the system remained 
 stationary while being held only by the 
 outby brake. The disabled brake test 
 verified that the system can be safely 
 operated on a grade, even if several 
 brakes are temporarily disconnected. 
 
 HAULAGE RATE 
 
 The objective of the haulage-rate tests 
 was to determine the maximum haulage ca- 
 pacity of the MBC units and to investi- 
 gate spillage sources. To measure the 
 instantaneous and total weights of coal 
 moved by the MBC system, an electronic 
 belt-scale system installed on the 48-in- 
 wide auxiliary belt was used. To obtain 
 a high haulage rate, the MBC system was 
 installed in a closed-loop configuration 
 (fig. 13). The MBC system was located in 
 the radius portion of the test rig. The 
 outby MBC unit dumped coal onto the 
 auxiliary belt, which dumped onto a 30- 
 ft-long, 36-in-wide flat belt. The flat 
 belt then dumped coal into a shuttle car, 
 which dumped back into the inby MBC unit 
 hopper. Run-of-mine (ROM) bituminous 
 
 Conventional belt units 
 
 Shuttle car 
 
 FIGURE 13.— Closed-loop configuration. 
 
15 
 
 coal was added to the system by loading 
 coal into the shuttle car. 
 
 The MBC was located in the radius por- 
 tion of the test rig so that the inby and 
 intermediate MBC units were at a 43° an- 
 gle to each other. This worst-case con- 
 figuration (fig. 14) occurred where the 
 two conveyors intersected at the cen- 
 ter of the 60° arc of the radius track 
 section. 
 
 During initial trials, belt-alignment 
 problems were encountered on the inter- 
 mediate unit. Prior to loading, the 
 belts were adjusted at the takeup to 
 track in the center of the rollers, but 
 the belts untracked as soon as the belts 
 were loaded. Be It -alignment problems 
 were not encountered during the initial 
 checkout haulage test when the MBC units 
 were in straight alignment. It is as- 
 sumed that the alignment problems were 
 caused by side loading from the inby 
 unit. With the inby and intermediate 
 units installed at an angle, coal at 
 the transfer point from the discharging 
 conveyor had momentum perpendicular to 
 the axis of the receiving conveyor. The 
 
 belt would misalign in response to this 
 side loading. Problems with coal dis- 
 charging from the inby unit and hitting 
 the suspension frame of the intermediate 
 belt also contributed to the belt-align- 
 ment problem, since spillage was falling 
 onto the return side of the intermediate 
 unit belt and jamming the tail roller. 
 Because of these belt-alignment problems, 
 two modifications were made before fur- 
 ther trials were attempted: (1) a 3/16- 
 in/ft crown taper was put onto the head 
 and tail rollers, and (2) the suspension 
 frame was modified to provide more area 
 for the coal to discharge. Crown taper 
 is commonly used on belt conveyor rollers 
 to improve tracking. Conveyor belts tend 
 to move toward the direction of great- 
 est tension, and the crown taper causes 
 the conveyor-belt tension to be greatest 
 at the center of the head and drive 
 rollers, thus making the conveyor belt 
 self-centered. 
 
 After the above modifications were com- 
 pleted, the haulage-rate trials were re- 
 started. Figure 15 shows the strip-chart 
 readout for the haulage-rate trial. An 
 
 FIGURE 14.— Monorail bridge conveyor units at maximum-angle relationship. 
 
16 
 
 1,200 
 
 10 
 TIME, s 
 
 FIGURE 15.— Haulage-rate plot. 
 
 8§ '> 200 
 
 2 K -C 
 
 < O ^ 800 
 I- 2 «/> 
 
 p 3 
 
 "i — i — i — | — i — i — i — t 
 Adding coai- 
 
 t — i — r— i — i — r 
 
 -i—\ — r 
 
 TZ 
 
 j^/amJHV *^ |l^f^7^ > *^^*^^**H*Mw4*<'^M>i*y w * l ^i 
 
 400 
 
 0t i i i i I i_i 
 
 J I l_l I l_l I I L 
 
 J I I I l__L 
 
 20 
 
 -i — i — i — r 
 
 J ■ ■ ■ i, 
 
 25 
 
 15 
 TIME, s 
 
 FIGURE 16.— Haulage rate and power plots during maximum haulage-rate trial. 
 
 30 
 
 average of 450 st/h of coal was handled 
 without experiencing problems with the 
 MBC system. The decreasing haulage rate, 
 after coal addition was stopped, was due 
 to spillage at the shuttle car. Spill- 
 age at the MBC transfer points was 
 negligible. 
 
 A second test was conducted to estab- 
 lish the maximum haulage rate of the MBC 
 system. Belt-motor power consumption was 
 monitored during this test, in addition 
 to haulage rate. Coal was added to the 
 closed-loop circuit until failure of the 
 flat auxiliary belt precluded additional 
 loading. The peak instantaneous loading 
 rate during this trial was 600 st/h (fig. 
 16). No problems were observed with 
 the MBC system during peak loading rates. 
 All belts remained in alignment, and 
 spillage at the transfer points was mini- 
 mal. The maximum observed conveyor-motor 
 power consumption was 16.8 kW for three 
 
 motors. These tests verified that the 
 MBC is capable of haulage at its design 
 specification of 600 st/h. 
 
 MINER LOADING TRIALS 
 
 The objective of the miner loading tri- 
 als was to verify the ability of the MBC 
 to simultaneously tram and receive coal 
 from the discharge boom of a continuous 
 miner, as would be done underground. A 
 Joy 16CM continuous miner was used to 
 load directly into the hopper of the inby 
 unit (fig. 17). The miner had a 24-in- 
 wide and 8-in-deep chain conveyor area. 
 A 15-st pile of wetted ROM bituminous 
 coal was placed in front of the contin- 
 uous miner. The continuous miner was 
 positioned inby the MBC system, which 
 was located in the radius portion of the 
 test rig. The outby MBC unit discharged 
 onto the 48-in auxiliary belt. A 10-st 
 
17 
 
 FIGURE 17.— Continuous miner loading directly into monorail bridge conveyor. 
 
 capacity shuttle car was used to receive 
 coal discharged from the auxiliary belt. 
 For each trial, the instantaneous load- 
 ing-rate instrumentation was started, the 
 miner was trammed into the coal pile, and 
 the miner operator directed the miner 
 tail boom toward the MBC hopper. The MBC 
 operator, located beside the inby MBC 
 motor-control case, trammed and steered 
 the MBC system as required to locate the 
 MBC hopper under the discharge from the 
 continuous miner. The miner advanced ap- 
 proximately 15 ft into the coal pile un- 
 til the pile was eliminated. After each 
 trial, the MBC and miner were backed up, 
 and the shuttle car dumped the coal in 
 front of the continuous miner. For sev- 
 eral trials, the miner was maneuvered to 
 simulate coal face cleanup operations. 
 Total tonnage for each trial was deter- 
 mined from the belt-scale totalizer. The 
 total tonnage loaded and maximum instan- 
 taneous MBC haulage rate for each trial 
 were: 
 
 Trial A - 10.1 st loaded at a maximum 
 rate of 690 st/h. 
 
 Trial B - 8.2 st loaded at a maximum 
 rate of 720 st/h. 
 
 Trial C - 12.9 st at a maximum rate of 
 720 st/h. 
 
 Trial D - 10.0 st loaded at a maximum 
 rate of 630 st/h. 
 
 Trial E - 7.6 st loaded at a maximum 
 rate of 660 st/h. 
 
 The miner operator had no problems 
 keeping the inby hopper of the MBC under 
 the miner tail boom as the miner trammed 
 into the coal pile. The MBC operator was 
 also able to maneuver behind the mine 
 during face cleanup operations. This 
 test sequence verified the ability of the 
 MBC to simultaneously convey coal and 
 tram. 
 
 RELIABILITY 
 
 To determine the reliability of the 
 conveyor portion of the MBC system, 
 the MBC was installed in a stationary 
 
18 
 
 closed-loop configuration. ROM bitumi- 
 nous coal was added to the circuit by 
 slow discharges from a 500-lb capacity 
 loader bucket into the hopper of the inby 
 unit. Coal continued to be added until 
 the belt-scale output showed an average 
 rate of 500 st/h. Recharges of coal were 
 occasionally necessary when spillage 
 losses in the circuit caused the rate to 
 fall to 300 st/h. All coal was wetted 
 prior to loading for dust control. 
 
 For the entire trial, the instantaneous 
 loading rate, the 48-in auxiliary belt 
 speed, the belt-scale load-cell output, 
 and the total MBC power consumption were 
 plotted on a strip-chart recorder. Dur- 
 ing the reliability trial, an event log 
 was maintained. Event description, time, 
 MBC conveyor hourmeter and totalizer 
 readings were recorded for each test 
 event. Water was applied to the under- 
 side of each MBC belt every hour to con- 
 trol dust generation. 
 
 During the reliability trial, the MBC 
 conveyors loaded 2,141 st of ROM coal 
 
 during 5.7 h, for an average loading rate 
 of 375 st/h. Loading-rate peaks of 600 
 st/h occurred several times during the 
 trial. One failure occurred at 1.3 h 
 into the trial: The conveyor drive cou- 
 pler on the inby MBC unit came apart 
 while the system was hauling at 400 st/h. 
 To repair the coupler, the conveyor drive 
 assembly was realigned with respect to 
 the head drive shaft, and the coupler was 
 replaced. The repair was accomplished by 
 two mechanics in approximately 2 h. One 
 adjustment was necessary at 4.1 h into 
 the trial because it was observed that 
 the outby unit belt was misaligned by 
 several inches. The belt takeup was 
 quickly adjusted without interfering with 
 coal haulage. 
 
 Figure 18 shows two 36-min, instantane- 
 ous loading rate, and total MBC power- 
 consumption traces. The upper trace oc- 
 curred at 3. 1 h into the trial. After 
 coal addition stopped, the average load- 
 ing rate was approximately 390 st/h. The 
 average power consumption for the same 
 
 V) 
 
 111 
 
 5 t- 1,200 |- 
 w a: 900 
 
 
 600 
 300 
 
 V) 
 Z -J 
 
 O 
 
 ■£ 
 
 or 
 
 24 
 20 
 
 -1 — r — 1 — 1 — 1 — 1 — 1 — r — 1 — 1 — 1 — 1 — 1 — r— 1 — 1 — 1 — r — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 — p — 1 — 1 — 1 — 1 — r 
 
 »■• Adding coal »h 
 
 lL U U « *»44.J' UM t» U * M i 
 
 1 — 1 1 1 1 1 1 i_i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 — 1 1 
 
 »- 2 ~ ,„« 
 
 z-<" 300 
 
 2« 
 
 2 -J 
 
 Adding coa 
 
 JL_JL L _L i. LJ. ±. J Lll J I L-J_ 1 I 1 ■ ' ■ 1 I I 1 I I I I I l_J L 
 
 TRIAL B TIME-^ 
 
 Eg 
 
 24 
 20 - 
 16 - 
 
 HO (/> 
 CD 2 
 5 O 
 
 o 
 
 TT-T 
 
 1 rn r 1 1 1 1 i 1 1 "t 1 i 1 1 1 1 1 1 1 t 
 , Sequence switch opened during trial 
 
 &£§* 12 --tfy^v^^^^" ■■ -L^ 
 
 ■ 1 'I ' i ' 1 1 ' 1 ' 1 ' 1 ' ■ 1 ■ 
 
 J I I I L J I I I I I 1 I I I I I 1 1 1 I 1 l_ 
 
 TRIAL B TIME 
 
 CHART SPEED= O.lmm/s 
 
 FIGURE 18. — Loading rate and power consumption during reliability trial. 
 
19 
 
 time was approximately 11 kW or approxi- 
 mately 15 hp; i.e., half the rated motor 
 capacity of 30 hp. The scattered peaks 
 and variations in power consumption were 
 probably due to very fast openings and 
 closings of one or more of the belt-slip 
 centrifugal switches, which in turn shut 
 the conveyor belt motors on and off. MBC 
 belt-speed variations were not noticed 
 during power-consumption variations. 
 
 The bottom trace was acquired at 4.1 h 
 into the trial when the system was being 
 restarted after a lunch break. After 
 coal addition stopped, the average load- 
 ing rate was 480 st/h. The average power 
 consumption for the same time was 12.5 
 kW. Observed variations in both total 
 MBC power consumption and loading rate 
 were dampened with time because of more 
 equal distribution of coal in the cir- 
 cuit. Midway through the bottom trace, a 
 belt-slip switch was opened while the 
 left was being cleaned. The belt clean- 
 ers at that time were tensioned against 
 the return belt by a counter-weight of a 
 lever arm. By pulling the lever arm, ex- 
 tra force could be applied to the belt 
 
 cleaner. In this instance, extra force 
 applied to the belt cleaner caused the 
 return belt to raise and lose contact 
 with the slip-switch roller. After these 
 trials, the counterweighted belt cleaners 
 were replaced with a compression-spring 
 tensioner device. 
 
 The reliability trial was terminated at 
 5.7 h into the trial because of a spill 
 at the intermediate discharge point that 
 was caused by excessive coal flow, which 
 buckled the hoop-type deflector. Coal 
 was being added to the system at the 
 time, and the haulage rate exceeded 600 
 st/h. This spill contributed greatly to 
 the total spillage amount that had accu- 
 mulated at the inby discharge point. Af- 
 ter the trial, spillage at both the inby 
 and intermediate transfer points was 
 raised. There was 700 lb of spillage un- 
 der the inby transfer point, and 4,650 lb 
 of spillage under the intermediate trans- 
 fer point. Figure 19 shows the spillage 
 under the inby transfer point. Prior to 
 the spill, it was observed that spillage 
 under the intermediate transfer point was 
 twice the amount under the inby transfer 
 
 FIGURE 19.— Spillage under inby monorail bridge conveyor transfer point. 
 
20 
 
 point, or approximately 1,400 lb. Based 
 on the lower prespill assumed value, 
 2,100 lb of spillage occurred during the 
 trial, and the total amount of coal 
 loaded was 2,141 st. Spillage rate dur- 
 ing this trial can then be computed as 
 0.05 pet of throughput. It is likely 
 that the spillage rate might be higher 
 during in-mine operation, since the sys- 
 tem would be occasionally tramming during 
 conveying operations. During the entire 
 reliability trial, the inby and interme- 
 diate conveyors were at a 5° angle to 
 each other, and the intermediate and 
 outby conveyors were at 20° angles. Dur- 
 ing previous trials, it was observed that 
 the amount of spillage at transfer points 
 increased rapidly as the angle between 
 the conveyor increased. After the tests, 
 the center of the hoop-type deflector was 
 bolted to the suspension frame to prevent 
 future buckling. 
 
 SYSTEM COMPATIBILITY 
 WITH LOW-BELT STRUCTURE 
 
 There are several ways that the outby 
 end of the MBC can be located to ensure 
 smooth coal transfer onto the section 
 belt: One way is to suspend the outby 
 unit from the monorail installed di- 
 rectly over the section belt, and another 
 is to attach the outby end of the outby 
 unit to a dolly supported by a low-belt 
 structure. 
 
 To demonstrate the compatibility of the 
 MBC system with a commercially available 
 low-belt structure, a 32-ft-long section 
 of low-belt structure and a dolly were 
 installed under the chain-suspended right 
 monorail track (fig. 9). The frame of 
 the low-belt structure, designed for use 
 with a 42-in-wide belt, was made of in- 
 terlocking roller assemblies and connect- 
 ing members. The low-belt structure was 
 extended to a total length of 32 ft by 
 the addition of framework made of 5—1/2— 
 in-wide channel sections. Rollers on the 
 bottom and cams on the side of the mating 
 dolly allowed easy mobility on the frame 
 of the low-belt structure. The low-belt 
 dolly was modified by adding an attach- 
 ment bracket. This bracket firmly at- 
 tached the outby MBC unit to the low-belt 
 dolly, while permitting the outby unit to 
 
 pivot in both horizontal and vertical 
 directions. A 42-in-long drawbar was at- 
 tached between the tram outby motor and 
 dolly bracket. The main power cable to 
 the MBC was then attached to the strain- 
 relief clamp of the low-belt dolly, so 
 that the power cable would always move 
 with the system. 
 
 No problems were observed as the en- 
 tire MBC system and dolly were repeatedly 
 trammed along the 32-ft, low-belt struc- 
 ture in the inby and outby directions. 
 The dolly moved smoothly on the low-belt 
 structure; the only jerking motion oc- 
 curred during starting and stopping be- 
 cause the outby tram motor was not rigid- 
 ly attached to the outby MBC unit. When 
 the system started tramming, force from 
 the outby tram motor pushing against the 
 drawbar tended to briefly lift the outby 
 motor and suspended monorail track. How- 
 ever, steady-state tramming motion was 
 quickly reached within 2 s because all 
 tram motors were operated at the same 
 speed. 
 
 The material-handling capability of the 
 dolly-mounted MBC system was not tested. 
 It is expected that transfer of material 
 from the outby MBC unit to the panel belt 
 would not be a problem in a dolly-mounted 
 configuration, since the dolly fixes the 
 outby unit at a constant height from the 
 panel belt, and skirt boards can be added 
 to the dolly as required. 
 
 SUSPENSION OF MONORAIL TRACK 
 BY CHAIN HANGERS 
 
 There are several ways of installing 
 special monorail track from the mine 
 roof: One is to rigidly attach the track 
 to roof plates anchored to the mine roof. 
 Another method is to chain-suspend the 
 monorail track from chain-hanger brackets 
 anchored to the mine roof. Roof plates 
 minimize the head room required for sus- 
 pension hardware, but they are difficult 
 to adjust and require two roof bolts. 
 Chain hangers allow easy height adjust- 
 ment and require only one roof bolt, 
 but require extra head room. Initial 
 test sequences were performed with the 
 monorail track rigidly attached to roof 
 plates. To determine if the MBC system 
 could tram on freely suspended monorail 
 
21 
 
 Chain 
 
 FIGURE 20.— Profile of chain-suspended monorail track. 
 
 FIGURE 21.— Chain hanger. 
 
 rail track, a 50-ft section of the right 
 monorail track was suspended from chain 
 hangers (fig. 20). To suspend the mono- 
 rail track, chain-hanger assemblies, us- 
 ing various-length, 1/4-in high-strength 
 alloy steel chain with attachment hard- 
 ware, were hung from the roof -bolt mount- 
 ing plates on 4-ft centers. Each chain 
 was held to the simulated mine roof by 
 a chain-hanger bracket, which permitted 
 adjustable chain height. The chain 
 was connected to the top of the monorail 
 track by a 1/2-in hex bolt welded to a 
 chain clevis (fig. 21). 
 
 A hydraulically powered rail bender 
 was utilized to make concave and convex 
 vertical curves in the inverted T-section 
 monorail track. The rail bender was op- 
 erated by clamping a section of monorail 
 track between a load ram and two pivot 
 points. The load ram was activated by 
 means of a hydraulic handpump. By us- 
 ing a displacement indicator on the rail 
 bender, specific angles could be made in 
 the track. The radius of the bend could 
 be controlled by changing the distance 
 between the load ram and pivot points. 
 The rail bender was then used to install 
 two convex bends of 3.7°, 32 in apart, on 
 the first 7-ft-long monorail track sec- 
 tion. This track section, previously on 
 a 6-1/2-pct upward grade, was bent to end 
 with a 6-1/2-pct downward grade. Addi- 
 tional track sections were then connected 
 to give the track a straight 6-1/2-pct 
 downgrade. When the top of the track 
 reached a height of 68 in from the 
 ground, a single concave bend was made so 
 that the end segment of the track was 
 parallel to the ground. In all cases, 
 each 7-ft-long track section was sus- 
 pended from the support structure by 
 chain hangers on 4-ft centers before the 
 next track section was connected. After 
 the entire 50-ft section of track was 
 suspended, several of the chain-hanger 
 lengths required adjustment to prevent 
 slack in the hanger assembly. The height 
 was adjusted by changing the chain link 
 in the adjustable hanging bracket. To 
 constrain sideways movement, 1/4-in chain 
 installed perpendicular to the monorail 
 tracks was used at the outby end of the 
 suspended monorail track. 
 
 After the 50-ft segment of monorail 
 track was suspended, the outby end of the 
 outby MBC unit was mounted on a low- 
 belt dolly, as described in the previous 
 
22 
 
 section. The ability of the MBC system 
 to tram on chain-suspended monorail track 
 was then observed. 
 
 No problems were experienced as the 
 dolly-mounted MBC system was repeatedly 
 trammed in both the inby and outby di- 
 rections on the chain-suspended mono- 
 rail track. The eight-wheel carrier as- 
 semblies negotiated a 13-pct change in 
 grade over a 3-ft distance without any 
 noticeable binding. Sideways movement 
 of the suspended monorail track was not 
 observed. 
 
 SYSTEM COMPATIBILITY WITH HOPPER-FEEDER 
 
 Although the inby MBC unit can be 
 loaded directly by a continuous miner, in 
 most cases, it would be desirable to In- 
 clude surge and breaker capabilities be- 
 tween the miner and the MBC. The Bureau 
 has developed a separate prototype mining 
 machine, the hopper-feeder-bolter (HFB), 
 to perform that task. The HFB is a cat- 
 mounted vehicle that includes a 5-st ca- 
 pacity surge hopper, an onboard lump 
 breaker, a variable-angle discharge boom 
 and an optional bolter-module (fig. 22) 
 to permit bolting beside a two-pass con- 
 tinuous miner. This provides the advan- 
 tage of eliminating face-to-face place 
 
 changes during the mining cycle. The 
 bolter module was removed and only the 
 hopper-feeder (HF) was used during trials 
 with the MBC. 
 
 To evaluate the ability of the HF to 
 load the MBC, a compatibility trial was 
 conducted. The HF was located inby the 
 MBC, and the MBC was loaded with coal 
 discharged from the HF. The low-profile 
 hopper on the MBC was removed to enable 
 the 16-in profile HF discharge boom to 
 fit between the top of the inby MBC unit 
 (32 in) and the underside of the monorail 
 track (59 in). As shown in figure 23, 
 there was little clearance between the HF 
 boom and the top of the inby MBC unit and 
 a very small target area on the MBC to 
 permit loading without spillage. During 
 the loading trial, the MBC was able to 
 haul all coal being discharged at the 
 maximum HF loading rate; however, exces- 
 sive spillage was observed at the trans- 
 fer point between units. An improved in- 
 terface between units would be required 
 before they could be used together. 
 Since the HF boom must clear the under- 
 side of the monorail track, the exact de- 
 sign of the interface will depend upon 
 the height of the monorail installation 
 at the mine site. 
 
 SUMMARY OF SURFACE TEST FINDINGS 
 
 Surface testing verified that the MBC 
 system properly performs its design func- 
 tions and is worthy of an in-mine trial. 
 Hightlights of the surface test program 
 are summarized below. 
 
 power consumption was 
 several tram-motor 
 
 • Tram-motor 
 measured for 
 configurations. 
 
 • The braking system is more than ade- 
 quate, as one functioning brake unit held 
 three loaded MBC units on a 6-1/2-pct 
 grade. 
 
 • The ability to haul the design ca- 
 pacity of 600 st/h was verified. 
 
 • The MBC was capable of being loaded 
 by a continuous miner. A maximum haulage 
 
 rate of 720 st/h was measured during the 
 miner loading trials. 
 
 • During a reliability trial, the MBC 
 system loaded 2,141 st of coal in 5.7 h 
 with only one minor coupler failure. 
 
 • The MBC was trammed with the outby 
 end supported by a dolly mounted on a 
 low-belt structure. 
 
 • The MBC was able to tram from mono- 
 rail suspended from roof plates and chain 
 hangers. 
 
 • The MBC is compatible with the HF, 
 which provides surge capacity and lump- 
 breaking capability inby the MBC. An im- 
 proved interface between the MBC and HFB 
 is required to suit mine conditions. 
 
 MODIFICATIONS 
 
 Numerous modifications were made to the 
 original system design to correct the 
 problems observed during surface testing. 
 
 A complete listing of modifications is 
 contained in appendix A. Major modifica- 
 tions included. 
 
23 
 
 *sa^ 
 
 FIGURE 22.— Hopper-feeder-bolter. 
 
 FIGURE 23.— Hopper- feeder compatibility trial. 
 
24 
 
 • Conveyor belt head and tail rollers 
 were crowned to improve belt tracking. 
 
 • The clearance area in suspension 
 frames was increased to create more area 
 for coal transfer between conveyors. 
 
 • Deflectors to direct coal flow and 
 control spillage were installed at con- 
 veyor transfer points; belt cleaners 
 were installed on the underside of each 
 conveyor. 
 
 • Remote-controlled steering was 
 installed. 
 
 • A limit switch to prevent the system 
 from tramming at the end of the monorail 
 was installed. 
 
 • A lightweight pendant control was 
 installed. 
 
 • The wheel base of the inby wheels 
 was increased for greater stability. 
 
 • The control circuitry was changed to 
 utilize an intrinsically safe control 
 pendant. 
 
 MINING 
 
 The review process for the MSHA experi- 
 mental permit was initiated in December 
 1984. Review of the control circuitry 
 revealed some problems. The system was 
 designed with intrinsically safe control 
 circuitry intermingled with 120-V ac pow- 
 er in a multiconductor control cable. To 
 remedy this situation, 480- to 120-V ac 
 transformers were installed into each 
 motor control box and additional safe 
 isolation relays were installed. The 
 main contactor allowed 120-V ac power in- 
 to each control box even when the main 
 switch was in the "off" position; this 
 was corrected by replacing the original 
 contactor in the master control box with 
 a circuit breaker located in a separate 
 enclosure. The changes made to meet MSHA 
 requirements are listed in appendix A. 
 
 PLANS 
 
 Based upon observations made during 
 surface testing, the following mine re- 
 quirements are suggested: 
 
 • The minimum working height of the 
 MBC is 48 in. The minimum working height 
 increases to 54 in if the outby end of 
 the MBC is supoprted by a 6-in high low- 
 belt structure (figs. 24-25). Additional 
 working clearance would ease cleanup un- 
 der the MBC. 
 
 • Maximum gradability of the system 
 is 6.5 pet without excessive tram motor 
 wear. Greater grades can be negotiated 
 at the expense of decreased tram-motor 
 life. 
 
 • A minimum entry width of 14 ft is 
 possible if 60° crosscuts are used and 
 intersection corners are rounded; how- 
 ever, a wider entry is desirable to allow 
 a walkway at all points on the clearance 
 (right) side of the system. 
 
 Roof bolt (typical load 2,0001b) 
 
 hanger 
 
 FIGURE 24. — Monorail installation with chain hangers. 
 
25 
 
 4" reference 
 
 Outbyunit 
 control box 
 
 54 M min 
 
 .5-hp 
 
 Monorail track -^ 
 ■•— | n by tram motor 
 
 Belt direction — Drawbar 
 
 Main power cable 
 
 T 
 
 8" reference 
 
 Power and control cables to other units 
 
 Low-belt structure Belt direction -»► 
 
 (panel belt) 
 
 FIGURE 25.— Monorail installation with roof plates over low-belt structure. 
 
 60° SIMPLE CURVE 
 System con be used ; _ 
 
 29° angle between A~B and BC 
 is <40° 
 
 NOTES: 
 
 Maximum angle between units is 40°, 
 Only RH turnouts are shown. 
 Angle of switches, 11°. 
 Arc of track sections: MK-3 and 
 MK-5, 12°; MK-4, 24°; MK-7, 19°; 
 andMK-8,3l°. (MK-7andMK-8 
 track not available at time of tests.) 
 All track curves on 24- ft radiurs. 
 All track is shown centered in 18-ft 
 entry. 
 
 _1 
 
 *^o Crib or post -»Q 
 
 *G 
 
 90° SIMPLE CURVE 
 System cannot be used; 
 49° angle between AB and 
 BC is > 40° 
 
 90° COMPOUND CURVE 
 
 System can be used; 
 
 34° angle between BC and C~D 
 
 is <40°. 
 
 However, 2 x FH=2 x 39ft=78ft. 
 
 This is too wide. Mine would require 
 
 extra roof support so that 2 x GH 
 
 <70ft. 
 
 KEY 
 
 ■ Splice plate 
 MK-5 Track designation 
 AB Represent units (each 24-ft long) 
 PT Point of tangency 
 
 FIGURE 26.— Monorail bridge conveyor track turnout plans. 
 
26 
 
 • The MBC was designed for 60° cross- 
 cuts using the 24-ft radius monorail 
 track, however, crosscuts of 90° can be 
 negotiated using a compound curve. In 
 any turnout configuration, the angle be- 
 tween MBC units must be less than 34° to 
 prevent unit-frame interference with each 
 other. An advantage of 60° crosscuts 
 is that spillage between units will be 
 minimized because potential spillage at 
 transfer points increases as the angle 
 between units increases. Figure 26 shows 
 track installation plans for both 60° and 
 90° crosscuts. 
 
 • Suporting the MBC system should not 
 be a problem because the eight-wheel car- 
 riers distribute conveyor weight over a 
 6-ft length of monorail track, which re- 
 sults in a typical load on each suspen- 
 sion point of less than 1 st. Although 
 not tested, resin bolts are recommended 
 over mechanical bolts to better withstand 
 tramming-induced vibration. 
 
 The MBC can be used for room-and-pillar 
 mining (figs. 27-29), longwall develop- 
 ment (fig. 30), or shortwall mining (fig. 
 31). For room-and-pillar mine plans, the 
 monorail track does not have to be in- 
 stalled in all mine entries. As illus- 
 trated in figure 27, the monorail track 
 would typically be installed over or 
 beside the panel belt in the center en- 
 try and in each crosscut. The combined 
 length of the inby MBC unit and the con- 
 tinuous miner enables raining in entries 
 that do not have monorail track in- 
 stalled. The hopper of the inby MBC unit 
 can be up to 20 ft from the last point 
 of monorail suspension. Assuming that a 
 typical continuous miner is 35 ft long, 
 the continuous miner cutterhead can be 
 up to 55 ft from the last point of mono- 
 rail installation (fig. 32). Various cut 
 plans are possible, depending on local 
 conditions. 
 
 Continuous miner 
 
 HFB surge car 
 
 1 2-unit system 
 
 Monorail track 
 
 FIGURE 27.— Five-entry mine plan. 
 
27 
 
 FIGURE 28.— Five-entry 60° mine plan with rooms. 
 
 M 
 
 5 | 12 10 
 
 23 
 
 26 24 22 
 
 20 
 
 16 
 
 1a 
 
 27 29 31 
 
 ^>K 
 
 ■ I 
 
 LEGEND 
 [7] Cut number 
 
 32 35 37 
 
 40 
 
 E*lE 
 
 M 
 
 1 l 1 1 1 > 1 » 1 * 1 1 H * l 1 
 
 v !y 1 . 1 1 . 
 
 39 41 M3 45 
 
 J--75- 
 
 •J 
 
 < t I » 1 1 ' 1 1 in 1 1 1 1 1 1 1 1 1 n 1 1 ^ ■ 
 
 «^ ^| l| >immm 1 > ■ t > 1 « » » i 
 
 I I M I I I > » » I t ■ < t * ) I » I I » 
 
 ■ I I I I M l I MM Ml IM I i l M 
 
 -18' 
 
 Return Intake Intake Be 
 
 FIGURE 29.— Seven-entry mine plan 
 
 t Track Intake Return 
 (power) 
 
28 
 
 Panel belt 
 
 MBC system Monorail track 
 
 Belt 
 
 Intake 
 
 Return 
 
 60° (typical) 
 
 FIGURE 30.— Mine plan for longwall panel-entry development. 
 
 mm mm 
 
 -r-Panel belt conveyor 
 
 :}:<~rj:!: 
 
 
 
 MBC system 
 
 Continuous miner 
 
 mm ml 
 
 Jr.- "I ^_J : ' 
 
 ,■„ ' . ' : ' ? . 9 l t . ' ■■..■ - ■-. ! 
 
 „ Chock 
 
 FIGURE 31.— Monorail bridge conveyor used with shortwall mining system. 
 
 ■fSKAtt* 
 
 A potential application of the MBC sys- 
 tem would be in longwall panel develop- 
 ment. As shown in figure 30, the 288-ft 
 MBC system would be of sufficient length 
 to advance two crosscuts of a three-entry 
 heading, thereby potentially reducing 
 longwall-panel development time. 
 
 An alternate use of the MBC system 
 would be to provide continuous haulage 
 capability for shortwall raining sec- 
 tions. Shortwall raining has the poten- 
 tial to provide productivity advantages 
 
 of longwall raining without high capital 
 costs. A major impediment to more short- 
 wall application is the lack of a contin- 
 uous haulage system. As shown in figure 
 31, the MBC connects the continuous miner 
 to the panel-belt conveyor with the mono- 
 rail track bolted to mine roof in the 
 headgate entry. In the face area, the 
 monorail is supported underneath chocks 
 with the provision that the lightweight 
 monorail track could be manually con- 
 nected after the chocks are advanced. 
 
29 
 
 rf5L.-L -„ 
 
 7 I^=m^m//=//7rm/r//i^/////L 
 
 55' 
 
 FIGURE 32.— Monorail bridge conveyor with continuous miner. 
 
 FIGURE 33.— Hopper-feeder-bolter. 
 
 If oversize material (over 12 in) is 
 regularly encountered during the mining 
 cycle, a crusher should be used inby the 
 MBC system to avoid clogging MBC trans- 
 fer points. The previously described 
 HFB with optional bolter removed, shown 
 in figure 33, can perform that task. 
 Additional advantages of using the HFB 
 between the continuous miner and MBC 
 
 are that (1) surge capacity is provided; 
 (2) an outby feeder breaker can be elimi- 
 nated; and (3) extra system reach is pro- 
 vided. As seen in figure 34, the contin- 
 uous miner cutterhead can be up to 80 ft 
 from the last point of monorail installa- 
 tion. If the MBC is used with the HFB, 
 the two systems could be connected (fig. 
 35). 
 
30 
 
 Miner operator 
 
 Hopper feeder operator 
 
 Miner- feeder 
 cable handler 
 
 <r ~l if Operator 
 
 Two- pass 
 continuous miner H °PP er feeder 
 
 ,nbyunlt Monorail track 
 
 80 ' 
 
 FIGURE 34. — Monorail bridge conveyor used with hopper-feeder. 
 
 62" min 
 
 take up 
 
 FIGURE 35.— Monorail bridge conveyor-hopper-feeder interface. 
 
 One operator is required for the entire 
 MBC system, although it may be desirable 
 to temporarily station a helper at the 
 outby transfer point to the panel belt 
 to assure proper transfer. Mine person- 
 nel should be instructed to stay on the 
 clearance side of the system where the 
 emergency shutoff switches are located. 
 
 In a continuous haulage mode with the 
 MBC positioned directly behind the con- 
 tinuous miner, the MBC operator would 
 control tramming and steering to follow 
 the miner. The pendant remote control 
 will allow the operator to be positioned 
 to avoid pinch points and to view loading 
 operations. Various hopper capacities 
 and profiles could be installed on the 
 inby end of the system to maximize the 
 target area for the miner operator. De- 
 pending upon the mine plan, the miner 
 power cable could be carried by the MBC. 
 
 Two methods of monorail track installa- 
 tion are possible. If lack of head room 
 is a problem, the monorail track can be 
 
 directly attached to the roof, using roof 
 plates (fig. 25). Another method, using 
 chain hangers, is shown in figure 24. 
 Roof plates require two roof bolts for 
 installation, while chain hangers require 
 one. Chain hangers permit monorail in- 
 stallation in high and uneven roof con- 
 ditions. Figure 8 shows the two types 
 of installation hardware. The size and 
 length of the roof bolt would depend upon 
 local mine conditions. Roof bolts that 
 are part of the roof-control plan cannot 
 be used for monorail suspension. Suspen- 
 sion on 4-ft centers is recommended for 
 straight track sections. Suspension on 
 3-ft centers is recommended for curved 
 track sections. 
 
 Monorail track can be installed either 
 on or off cycle with the cutting plan, 
 depending on the mine and cut plan 
 selected. Oncycle installation plans 
 would require the roof-bolter crew to 
 install monorail track in a cut immedi- 
 ately after the cut Is bolted. Off-cycle 
 
31 
 
 KEY 
 ■ Splice plate 
 
 MK-5 monorail track designation; 
 see figure 7. 
 
 FIGURE 36.— Monorail track installation plan. 
 
 installation plans would allow monorail- 
 track installation during an idle shift. 
 Monorail-track layout must be consistent 
 with as-cut mine geometry to ensure ade- 
 quate clearance at turnouts. Figure 36 
 
 shows a typical track layout for 18-ft- 
 wide entries and 60° crosscuts. The 
 track should always be installed to main- 
 tain clearance for personnel at all 
 points on the right side of the MBC. 
 
 CONCLUSIONS 
 
 The MBC system, which includes the HF 
 as a beneficial option, is a prototype 
 continuous face haulage system that has 
 the potential to significantly increase 
 productivity and offer additional safety. 
 Extensive surface tests were conducted 
 by the Bureau to evaluate equipment per- 
 formance criteria and to identify and 
 make necessary modifications before con- 
 ducting an underground trial. Successful 
 test results under simulated mine condi- 
 tions indicate that this innovative haul- 
 age system offers the mining industry 
 
 potential benefits for increased produc- 
 tivity, while providing increased person- 
 nel safety. Mining plans were developed 
 that offer application of the MBC system 
 for room-and-pillar, longwall develop- 
 ment, and shortwall mining sections. A 
 patent (U.S. Pat. 4,159,757) was granted 
 to the Bureau in 1979 for the basic MBC 
 concept. An in-mine trial is planned at 
 a midwestern underground coal mine, using 
 the MBC and HF as a continuous face haul- 
 age system. 
 
32 
 
 APPENDIX A.— MODIFICATIONS TO THE MONORAIL BRIDGE CONVEYOR SYSTEM 
 
 Date 
 
 Modifications 
 
 Reason 
 
 Sept. All interconnecting power and con- 
 1982 trol cables between units were 
 shortened. 
 
 The original cables were too long and 
 dropped onto the floor when connected. 
 The extra weight also caused the conveyor 
 units to lean toward the cables. 
 
 Sept. New holes were drilled in the sus- 
 1982 pension yokes to lower the inby 
 
 attachment point of the units by 
 
 2 in. 
 
 Additional clearance was required at the 
 transfer points between units so that 
 spillage guards could be installed. 
 
 Sept. Spillage guards were installed on 
 1982 the inby end of each unit. Rub- 
 ber belting was installed to pro- 
 vide 6 in of overlap on each side 
 of the 36-in-wide conveyor belt. 
 
 Oct. Replaced pneumatic tires on the 
 1982 inby tram drive with solid rubber 
 tires. 
 
 Preliminary loading trials revealed exces- 
 sive spillage at the transfer points. 
 The spillage guards also helped to center 
 the coal on the conveyor belt. 
 
 The original pneumatic tires required 
 excessive steering effort (>50 ft* lb). 
 Less than 20 ft* lb of effort was required 
 with the solid tire. 
 
 Nov. A steering motor, gearbox, and re- 
 1982 mote steering-control circuit 
 
 were installed for the inby tram 
 
 drive. 
 
 Nov. Isolation relays to provide in- 
 1982 trinsically safe circuits were 
 
 added to the tram and steering 
 
 controls. 
 
 The original manual steering was undesir- 
 able because it was difficult to operate, 
 and it put the operator in an unsafe 
 position. 
 
 Intrinsically safe circuits were required 
 to enable use of nonexplosionproof limit 
 switches and pendant control. 
 
 Nov. Grease fittings were added to the 
 1982 conveyor drive couplers. 
 
 Nov. The spacing between the conveyor 
 1982 return roller for the belt- 
 sequence switch and the conveyor 
 return roller for the belt-slip 
 switch was increased from 24 to 
 48 in. 
 
 Additional lubrication was required to 
 prevent frequent coupler disengagement. 
 
 The original, closely spaced, return 
 rollers were not turned by the belt dur- 
 ing loading trials, because increased 
 belt tension caused the belt to lift from 
 the rollers. 
 
 Nov. A 3/16-in/ft crown taper was added Belt-alignment problems were experienced 
 1982 to the head and tail rollers. during coal loading trials. Crown taper 
 
 tends to self-center the conveyor belt. 
 
 Dec. Adjustable hoop-type angle deflec- 
 1982 tors were added on the outby end 
 of each unit. 
 
 Deflectors were required to center the 
 coal transfer to minimize spillage. The 
 hoop-type deflectors were required to 
 prevent coal from hitting the suspension 
 yoke when two units were at an angle. 
 
33 
 
 MODIFICATIONS TO THE MONORAIL BRIDGE CONVEYOR SYSTEM— Continued 
 
 Date 
 
 Modifications 
 
 Reason 
 
 Dec. 
 1982 
 
 Jan. 
 1983 
 
 The profile of the suspension yoke The original suspension yoke was struck by 
 was modified to allow a greater coal when units were at their raaxiraum- 
 opening for coal transfer. angle relationship. 
 
 Compression-spring-type belt 
 cleaners were installed under- 
 neath the head roller. 
 
 Belt cleaners were required because coal 
 tended to accumulate on the underside of 
 the conveyor belting, causing belt mis- 
 alignment and opening of the slip switch. 
 
 Jan. A lightweight pendant control was 
 1983 installed. 
 
 June The wheel base between the 9-in- 
 1983 wide inby rubber tires was in- 
 creased from 12-in centers to 
 38-in centers. 
 
 Originally, an explosionproof control unit 
 was installed. This heavy unit was awk- 
 ward to use and only had controls for 
 conveying and tramming. Extra controls 
 were required because a steering motor 
 was previously added. 
 
 Tramming tests proved that the inby unit 
 was unstable with original close-wheel 
 base. Stability is required to prevent 
 belt misalignment. 
 
 June The inby tram drive was changed to 
 1983 a gear-speed reducer mounted be- 
 tween the inby rubber tires. 
 
 June Limit switches were installed to 
 1983 limit the allowable steering arc 
 of the inby wheel carriage. 
 
 The original chain and sprocket drive was 
 unreliable and had poor ground clearance. 
 
 Without limit switches, the wheel carriage 
 turned until stopped by mechanical inter- 
 ference. This in turn would overload the 
 steering motor. 
 
 June A limit switch was installed to 
 
 1983 detect when the inby monorail 
 carrier reached the end of the 
 monorail track. 
 
 Aug. A heavier inby tram-motor torque 
 
 1984 arm was anchored to both sides of 
 the through-bolts on the inby 
 tram-speed reducer. 
 
 Aug. Cast bearings were installed to 
 1984 support the steering shaft. 
 
 This switch prevents the monorail carrier 
 from tramming off the inby end of the 
 monorail track, thereby avoiding a possi- 
 ble safety hazard and operational delay. 
 
 The original torque arm was only attached 
 to one side of the speed reducer, and it 
 failed during tramming tests. 
 
 The original pressed bearings did not 
 resist the lateral thrust produced by 
 the steering shaft. This caused the 
 steering-shaft key to disengage from the 
 drive coupler. 
 
 Nov. The inby tram drive was changed 
 1984 from two- to one-wheel drive. 
 
 The original design with both wheels 
 mounted on a solid shaft required exces- 
 sive torque requirements for steering, 
 since the wheels would slide instead of 
 roll during steering maneuvers. 
 
34 
 
 MODIFICATIONS TO THE MONORAIL BRIDGE CONVEYOR SYSTEM — Continued 
 
 Date 
 
 Nov. 
 1984 
 
 Dec. 
 1984 
 
 Feb. 
 1985 
 
 Modifications 
 
 A brake was added to tbe steering 
 motor. 
 
 Reason 
 
 The brake was required to lock the steer- 
 ing carriage when the steering motor was 
 not in operation. 
 
 A new explosionproof steering con- The control box was required for steering 
 
 trol box was installed on the controls, 
 inby unit. 
 
 A 5/16-in-thick MSHA-approved PVC The original, 3/16-in-thick belt was not 
 
 conveyor belting was installed in adequate for underground use. 
 all units. 
 
 Feb. 
 1985 
 
 Feb. 
 1985 
 
 Several 4-in-diam clearance holes 
 were burned into the conveyor 
 frame to allow better access to 
 the conveyor drive coupler. 
 
 The original 1.5-in-diara hole made coupler 
 adjustment difficult. 
 
 Gussets were added to the sides of The switch mounting frames would be prone 
 the sequence and slip-switch to damage during MBC installation because 
 mounting frame. they extended below the main conveyor 
 
 frame. 
 
 Mar. The 480-V ac to 120-V ac trans- 
 1985 formers were installed into each 
 
 motor control box to power system 
 
 controls. 
 
 Mar. Isolation relays to provide in- 
 1985 trinsically safe sequence-switch 
 
 circuits were installed into each 
 
 control box. 
 
 Modification was required to meet MSHA re- 
 quirements. Originally, 120-V ac control 
 power for all units was supplied by one 
 transformer in the master control box; 
 however, this 120-V ac power was inter- 
 mingled with intrinsically safe control 
 wiring in a multiconductor cable. 
 
 Modification was required to meet MSHA 
 requirements. Previously, the 120-V ac 
 sequence-switch circuits were inter- 
 mingled in the multiconductor cable with 
 intrinsically safe circuits. 
 
 Mar. The brake overhead indicator lamps These items were removed to provide space 
 1985 and associated relays were re- for the transformer and isolation relays 
 
 moved from each motor control 
 
 box. 
 
 Mar. A 480-V ac to 120-V ac and 12-V ac The 120-V ac power was required for steer- 
 1985 dual secondary transformer was ing control, and 12-V ac power was re- 
 added to the steering control quired for lighting, 
 box. 
 
35 
 
 Date 
 
 MODIFICATIONS TO THE MONORAIL BRIDGE CONVEYOR SYSTEM— Continued 
 Modifications Reason 
 
 Mar. A main circuit breaker explosion- 
 1985 proof control box was added to 
 the MBC control system. 
 
 Modification was required to meet MSHA re- 
 quirements. Previously, the contactor in 
 the master control was the main circuit- 
 interrupting device; however, with the 
 contactor, there was 120-V ac power in 
 all units, even when the main power 
 switch was in the "off" position. 
 
 A new main breaker box was required be- 
 cause the existing master control box 
 did not have an opening for a circuit- 
 breaker reset handle. 
 
 Mar. Fuses were removed from the line 
 1985 side of the 480-V ac transformer 
 in the master control box. 
 
 If the fuses were left in, the master con- 
 trol box would require a panel-interlock 
 switch. 
 
 Mar. The ground-monitor circuit was 
 1985 removed from the master control 
 box. 
 
 The circuit would be redundant with the 
 load-center ground-monitor circuit. 
 
 Mar. An explosionproof junction box was 
 1985 added on the inby unit so that 
 both headlights could receive 
 power from one cable exiting the 
 steering control box. 
 
 Mar. An explosionproof junction box was 
 1985 added to the outby unit so that 
 both taillights could receive 
 power from one cable exiting the 
 master control. 
 
 An extra cable-entrance gland was required 
 in the steering control box for the 
 steering control brake. 
 
 An extra cable-entrance gland was required 
 in the master control box for the main- 
 breaker shunt-trip cable. 
 
 Apr. All interconnecting cables were 
 1985 placed in MSHA-approved flame- 
 resistant hose conduit. 
 
 Modification was required to meet MSHA 
 requirements. 
 
 June New cable hangers were installed 
 1985 on all units. The new cable han- 
 gers acted as trays and could 
 hold several cables. 
 
 Previously, separate cable hangers were 
 installed for each interconnecting cable. 
 This made adjustments awkward. 
 
 June Tapped mounting bosses were in- 
 1985 stalled on the inby end of each 
 unit. 
 
 The mountings were required to permit 
 rapid attachment of a changeout bracket. 
 The bracket is connected to a monorail- 
 suspended chain hoist when unit changeout 
 is required. 
 
 688 365 
 
 U.S. GOVERNMENT PRINTING OFFICE: 1987 605-01 7'60 070 
 
 INT.-BU.OF MINES,PGH.,PA. 28526 
 
U.S. Department of the Interior 
 Bureau of Mines— Prod, end Distr. 
 Cochrane Mill Roed 
 P.O. Box 18070 
 Pittsburgh. Pa. 15236 
 
 OFFICIALflUSINESS 
 PENALTY FOR PRIVATE USt MOO 
 
 [ J Do not wi sh to recei ve thi s 
 material, please remove 
 from your mailing list* 
 
 | "l Address change* Please 
 correct as indicated* 
 
 AN EQUAL OPPORTUNITY EMPLOYER 
 

 
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