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Unformatted text preview: Prepared by the Engineering Conference of the Conveyor Equipment Manufacturers Association Belt Conveyors for Bulk Materials FIFTH EDITION PDF Version July, 2002 Published by the Conveyor Equipment Manufacturers Association Copyright © 2002 by The Conveyor Equipment Manufacturers Association. All rights reserved. This book may not be reproduced in any form without written permission from CEMA. Printed in the United States of America Page layout and editing by The Scribe and Word Warriors. Printing (last digit): 9 8 7 6 5 4 3 2 Library of Congress Cataloging in Publication Data Conveyor Equipment Manufacturers Association. Engineering Conference. Belt conveyors for bulk materials. Includes index. 1. Belt conveyors. 2. Bulk solids handling. 1. Title. TJ1390.C65 1979 621.8’675 78-31987 ISBN 1-891171-49-6 PDF Version of ISBN 1-891171-18-6 Contents List of Figures xiv List of Tables xxv Preface xxix Acknowledgments xxxi Introduction xxxiii CHAPTER 1 Belt Conveyor General Applications and Economics 1 Introduction 2 Conveying of a Variety of Materials 2 Wide Range of Capacities 2 Adaptability to Path of Travel 4 Steep Angle Conveying 5 Loading, Discharging, and Stockpiling Capabilities 7 Process Functions 9 Reliability and Availability 10 Environmental Advantages 11 Safety 12 Low Labor Costs 12 Low Power Costs 13 Low Maintenance Costs 13 Long-Distance Transportation 13 High Horsepower, High Tension Conveyors 13 Owning and Operating Costs 14 Present Worth: Required Rate of Return 16 Summary 18 v Contents CHAPTER 2 Design Considerations 19 Conveyor Arrangements 20 Summaries of Chapters 3-14 25 Characteristics and Conveyability of Bulk Materials (Chapter 3) 25 Capacities, Belt Widths, and Speeds (Chapter 4) 25 Belt Conveyor Idlers (Chapter 5) 26 Belt Tension, Power, and Drive Engineering (Chapter 6) 26 Belt Selection (Chapter 7) 26 Pulleys and Shafts (Chapter 8) 27 Vertical Curves (Chapter 9) 27 A Guide to Steep Angle Conveying (Chapter 10) 27 Belt Takeups, Cleaners, and Accessories (Chapter 11) 27 Conveyor Loading and Discharge (Chapter 12) 28 Conveyor Motor Drives and Controls (Chapter 13) 28 Operation, Maintenance, and Safety (Chapter 14) 28 CHAPTER 3 Characteristics and Conveyability of Bulk Materials 29 Material Characteristics 30 Behavior of Materials on a Moving Belt 31 Effect of Inclines and Declines 31 CHAPTER 4 Capacities, Belt Widths, and Speeds 45 Belt Widths 46 Lump Size Considerations 46 Belt Speeds 46 Belt Conveyor Capacities 47 Troughed Belt Load Areas—Standard Edge Distance 49 Flat Belt Load Areas—Standard Edge Distance 51 Belt Conveyor Capacity Tables and Their Use 52 CHAPTER 5 Belt Conveyor Idlers 55 Idler Requirements 56 Idler Classifications 56 General Types of Belt Conveyor Idlers 56 Carrying Idlers 57 Return Idlers 57 Troughing Carrying Idlers 58 Impact Idlers 59 Belt Training Idlers, Carrying 60 Suspended or Garland Idlers 61 Return Idlers 62 Flat Return Idlers 62 Self-Cleaning Return Idlers 62 Return Belt Training Idlers 63 Two-Roll “Vee” Return Idlers 63 vi Contents Idler Spacing 64 Return Idler Spacing 65 Carrying Idler Spacing at Loading Points 65 Troughing Idler Spacing Adjacent to Terminal Pulleys 65 The Selection of Idlers 67 Rating and Idler Life 67 Idler Selection Procedure 67 Type of Material Handled 68 Lump Size Considerations 68 Idler Load 68 Effect of Load on Predicted Bearing L10 Life 68 Belt Speed 68 Roll Diameter 69 Environmental, Maintenance, and Other Special Conditions 69 Special Conditions 69 Idler Selection Procedure 70 Example Idler Selection 78 Belt Alignment 82 CHAPTER 6 Belt Tension, Power, and Drive Engineering 85 Basic Power Requirements 86 Belt Tension Calculations 87 Compilation of Components of Te Summary of Components of Te 96 102 CEMA Horsepower Formula 103 Drive Pulley Relationships 104 Wrap Factor, Cw 104 Wrap Factor with Screw Takeup 105 Wrap θ (Arc of Contact) 106 Dual-Pulley Drives 106 Drive Arrangements 109 Maximum and Minimum Belt Tensions 113 Maximum Belt Tension 113 Starting and Stopping Maximum Tension 113 Minimum Belt Tension, Tmin 113 Tension Relationships and Belt Sag Between Idlers 114 Graduated Spacing of Troughing Idlers 114 Analysis of Belt Tensions 117 Belt Tension Examples 127 Belt Tension Calculations 129 Acceleration and Deceleration Forces 136 Belt Stress 136 Vertical Curves 136 Loss of Tension Ratio 136 Load Conditions on the Belt 136 Coasting 136 Takeup Movement 137 Effect on Material Carried 137 Festooning 137 Power Failure 137 vii Contents Braking Tensions Taken by Return Run and Tail Pulley 137 Analysis of Acceleration and Deceleration Forces 138 Acceleration 138 Deceleration 138 Calculation of Acceleration and Deceleration Forces 138 Design Considerations 139 Necessary Assumptions 140 Calculations 140 Conveyor Horsepower Determination — Graphical Method 141 Determining Required Horsepower —Graphical Method 141 Examples of Belt Tension and Horsepower Calculations — Six Problems 145 Belt Conveyor Drive Equipment 177 Belt Conveyor Drive Location 177 Belt Conveyor Drive Arrangement 177 Speed-Reduction Mechanisms 177 Drive Efficiencies 180 Mechanical Variable Speed Devices 181 Creeper Drives 181 Backstops 182 Determine Need and Capacity of Backstop, Inclined Conveyors 183 Brakes 183 Mechanical Friction Brakes 184 Eddy-Current Brakes 184 Plugging the Motor 185 Dynamic Braking 185 Regenerative Braking 185 Brakes and Backstops in Combination 185 Restraint of Declined Conveyors 185 Backstop and Brake Recommendations 186 Deceleration by Brakes 186 Devices for Acceleration, Deceleration, and Torque Control 186 Starting the Conveyor 186 Controlled Acceleration 187 Brake Requirement Determination (Deceleration Calculations) 189 Material Discharged During Braking Interval 189 Forces Acting During Braking or Deceleration 190 Brake Location 191 Braking Torque 191 Brake Heat Absorption Capacity 191 Brake Calculations 192 CHAPTER 7 Belt Selection 197 Factors in the Composition of Conveyor Belting 199 Conveyor Belt Covers: Characteristics, Composition, and Design 199 General Purpose Belting 200 Special Purpose Belting 201 Cover Considerations 202 Loading Considerations 205 Breakers 206 Molded Edge Belting 206 viii Contents Cut/Slit Edge Belting 206 Steel Cord Belt Covers 206 The Belt Carcass 207 Carcass Types 207 Textile Reinforcements 208 Steel Reinforcements 211 Vulcanized Splice 213 Mechanically Fastened Splice 214 Belt and System Considerations 215 Elongation 215 Troughability and Load Support 215 Impact Resistance 216 Lump Weight Factor 218 Conveyor Belt Selection 218 Tension Ratings 218 Pulley Face 219 Service Conditions 220 CHAPTER 8 Pulleys and Shafts 225 Conveyor Pulley Assemblies 226 Pulley Types 226 Standard Steel Drum Pulleys 226 Standard Steel Wing Pulleys 228 Advantages of Using ANSI Standards 229 Mine Duty Pulleys 229 Engineered Pulleys 229 Pulley Overloads 233 Pulley Diameters 233 Pulley Face Widths 234 Pulley Crown 235 Pulley Weights 235 Pulley Lagging 235 Thickness and Attachment 235 Lagging Hardness 236 Lagging Grooving 236 High Tension Applications 236 Shafting 236 Shaft Materials 237 Resultant Radial Load 237 Shaft Sizing by Stress Limit 237 Shaft Sizing for Deflection 239 CHAPTER 9 Vertical Curves 241 Concave Vertical Curves 242 Design of Concave Vertical Curves 243 Graphical Construction of Concave Vertical Curve 251 Precautions for the Design of Vertical Concave Curves 252 ix Contents Convex Vertical Curves 252 Design of Convex Vertical Curves 254 Idler Spacing On Convex Curves 255 Use of Bend Pulleys for Convex Curves 258 CHAPTER 10 A Guide to Steep Angle Conveying 259 Incline Limitations with Conventional Conveyors 260 Molded Cleat Belts 261 Large Cleat/Fin Type Belts 268 Pocket Belts 270 Totally Enclosed Belts 273 Sandwich Belts 273 CHAPTER 11 Belt Takeups, Cleaners, and Accessories 279 Belt Takeups 280 Belt Stretch or Elongation 280 Takeup Movement 280 Manual Takeups 281 Automatic Takeups 282 Cleaning Devices 284 Analyzing Carryback 285 Cleaners and Conveyors 286 The Systems Approach to Belt Cleaning 286 Maintaining Cleaning Pressure 288 Belt Cleaners and Horsepower Requirements 288 Belt Cleaners and Top Cover Wear 288 The Importance of Maintenance 289 Specialized Cleaning Systems 289 Handling the Removed Material 291 Belt Turnovers 292 Pulley Wipers 292 Return-Run Belt Cleaning 293 Belt Conveyor Accessory Equipment 295 Weather Protection 295 Spillage Protection: Wing-Type Pulleys 297 Tramp Iron Detectors 297 Conveyor Belt Scales 298 Sampling Devices 298 CHAPTER 12 Conveyor Loading and Discharge 301 Loading the Belt 302 Direction of Loading 302 Transverse Belt Displacement 304 Loading an Inclined Belt Conveyor 304 Impact at Loading Point 304 x Contents Loading Chutes and Skirtboards 306 Loading Chutes 306 Skirtboards 308 Feeders 314 Screw Feeders 314 Belt Feeders 315 Drag-Scraper Feeders (Bar Drag Feeders) 315 Apron Feeders 315 Reciprocating Plate Feeders 315 Vibrating Feeders 316 Rotary-Vane Feeders (Pocket Feeders) 316 Rotary-Drum Feeders 316 Rotary-Table Feeders (Disc Feeders) 316 Traveling Rotary-Plow Feeders 317 Feed-Control Gates 317 Methods of Discharging from the Belt 317 Discharge Over-the-End Pulleys 318 Discharge Chutes 318 Lowering Chutes 320 Trippers 321 Stationary (Fixed) Tripper 323 Typical Movable Tripper 323 Tripper Discharge Through Auxiliary Arrangements 324 Plows 325 Plows Discharging to One Side 325 Plows Discharging to Both Sides 326 Discharge Trajectories 326 Calculating and Plotting Normal Material Trajectories 327 Horizontal Belt Conveyor Trajectories 330 Inclined Belt Conveyor Trajectories 332 Declined Belt Conveyor Trajectories 333 Plotting the Trajectory 334 Examples of Trajectories 337 CHAPTER 13 Conveyor Motor Drives and Controls 343 Introduction 344 Conveyor Belt Evaluation Criteria 344 Belt Drive System 344 Electric Motor Attributes 344 Belt Drive Attributes 349 Conveyor Drive Systems Overview 352 AC Induction Motor with Full Voltage Starting and Direct Couplings 353 AC Induction Motor with Reduced Voltage Starting and Direct Coupling 354 Wound Rotor AC Motor and Direct Coupling Drive 356 DC Motor and Direct Coupling 360 AC Induction Motor with Variable Frequency Control and Direct Coupling 364 AC Induction Motor with Full Voltage Starting and Fixed Fill Fluid Coupling 366 AC Induction Motor with Full Voltage Starting and Variable Fill Hydrokinetic Coupling 369 AC Induction Motor and Variable Mechanical Transmission Coupling 369 Other Conveyor Drives 371 xi Contents Conveyor Belt Controls 372 Drive Type Controller 372 Starting, Running, and Stopping Control Algorithms 372 Belt Protection Controls 373 Belt Control 375 Belt Control Apparatus 376 Conclusion 377 CHAPTER 14 Operation, Maintenance, and Safety 379 Operation 380 Maintenance 380 Safety 383 Guidelines for Safe Operation and Maintenance 384 APPENDIX A Guide for Use of SI (Metric) Units 387 Conversion Factors 388 Example 388 Example 388 Example 388 Metric Practice and Units for Mass, Force, and Weight 390 Mass, Force, and Weight 390 SI (Metric Units) for Belt Conveyor, Belt Tension, and Horsepower Calculations 392 Metric Use of CEMA Belt Tension Formulas 392 Problem 394 Frequently Used Conversion Formulas 396 Comparison of Belt Tensions 397 Comparison of Belt Velocities 397 APPENDIX B Nomenclature 399 APPENDIX C Belt Tension to Rotate Pulleys APPENDIX D Conveyor Installation Standards For Belt Conveyors Handling Bulk Materials 407 405 Introduction 408 Conveyor Stringer Alignment 409 Parallel 409 Straightness 409 Squareness 410 Level 410 Pulley and Shaft Alignment 411 Reducer/Motor Base Installation Tolerances 412 Fabricated Structural Bases 412 Concrete Supports 412 Structural Steel Supports 413 xii Contents Flexible Coupling Alignment 413 Idler Alignment 415 Belt Alignment 415 Empty Run-in 416 Full Load Run-in 417 Helpful Hints 417 Skirtboard Adjustment 417 Idler Lubrication 418 Manufacturer's Recommendation 418 Type of Lubricant 418 Idler Construction 418 xiii List of Figures CHAPTER 1 Belt Conveyor General Applications and Economics Figure 1.1 Figure 1.2 Figure 1.3 Figure 1.4 Figure 1.5 Figure 1.6 Figure 1.7 Figure 1.8 Figure 1.9 Figure 1.10 Figure 1.11 Figure 1.12 Figure 1.13 Figure 1.14 Figure 1.15 Figure 1.16 Figure 1.17 Figure 1.18 60-inch conveyor carries large lumps of abrasive ore on incline. 3 96-inch conveyor at high-capacity coal-loading facility. 3 Regenerative conveyor lowers coal across existing terrain in direct path from mine. 4 Corrugated metal cover over the belt provides weather and environmental protection. 5 Horizontal curve conveyor, conveying following natural terrain. 5 Multiple loading stations feed ore to slope conveyor in open-pit mine. 6 Rail-mounted hopper with feeder provides loading along full length of conveyor. 6 Multiple feeders in tunnel beneath stockpile provide efficient reclaiming and blending. 7 Material discharging over conveyor head pulley. 7 Power-driven twin trippers distributing coal in power plant. 7 Double-winged stacker discharging into high-capacity stockpiles on either side of the feeding conveyor. 8 Circular stacker reclaimer simultaneously stacks and reclaims over 3,000,000 cubic feet of wood chips at a major paper mill. 8 Shuttle belt conveyors load and trim taconite pellets onto ore vessel on Great Lakes. 8 Self-unloading ship with 78-inch discharge conveyor unloads iron ore pellets at 10,000 tph. 9 Rail-mounted ship unloaders feed 60-inch conveyor system at steel company. 9 V-type plow diverts foundry sand from flat belt conveyor. 9 Self-cleaning cross belt magnetic separator. 9 Belt scales monitor rate with varying degrees of accuracy to provide both inventory and process control. 10 xiv List of Figures Figure 1.19 Figure 1.20 Figure 1.21 Figure 1.22 Figure 1.23 CHAPTER 2 Multi-stage sampling systems are used in either the in-line or cross belt configurations to give desired process information on material specifications. 10 Operator controls entire conveyor system from control center with graphic display panels and push-button console. 11 Conveyor in completely enclosed gallery carries its load safely overhead, avoiding any interference from highway or rail traffic. 11 Overland conveyor system utilizing a concrete support structure provides a pleasing appearance blending with the landscape. 11 Tubular galleries provide opportunity to optimize shop assembly of components. 12 Design Considerations Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 2.7 Figure 2.8 Figure 2.9 Figure 2.10 Figure 2.11 Figure 2.12 Figure 2.13 Figure 2.14 Figure 2.15 Figure 2.16 Figure 2.17 Figure 2.18 Figure 2.19 Nomenclature of components of a typical belt conveyor. 20 Horizontal belt. 21 Horizontal and ascending path, when space will permit vertical curve and belt strength will permit one belt. 21 Ascending and horizontal path, when belt tensions will permit one belt and space will permit vertical curve. 21 Possible horizontal and ascending path, when space will not permit a vertical curve or when the conveyor belt strength requires two belts. 21 Ascending and horizontal path, when advisable to use two conveyor belts. 21 Possible horizontal and ascending path, when space will not permit vertical curve but belt strength will permit only one belt. 21 Compound path with declines, horizontal portions, vertical curves, and incline. 21 Loading can be accomplished, as shown, on minor inclines or declines. 21 Traveling loading chute to receive materials at a number of points along conveyor. 22 Discharge over end pulley to form conical pile. 22 Discharge by traveling tripper or through the tripper to the storage pile. See figure 2.14. 22 Discharge over either end-pulley of a reversible shuttle belt conveyor. 22 Discharge from tripper to one side only, to both sides, or forward again on conveyor belt. 22 Discharge by fixed trippers with or without cross conveyors to fixed piles or bin openings. 22 Discharge by traveling or stationary trippers to ascending cross conveyors carried by tripper. 22 Discharge by hinged plows to one or more fixed locations on one or both sides of conveyor plows. Device can be adjusted for proportioned discharge to several places. 22 Discharge by traveling or stationary tripper carrying reversible shuttle belt. 22 This overland conveyor following the natural terrain has an undulating profile with several concave and convex curves. 23 xv List of Figures Figure 2.20 Figure 2.21 Figure 2.22 Figure 2.23 CHAPTER 3 Characteristics and Conveyability of Bulk Materials Figure 3.1 CHAPTER 4 Figure 4.2 Figure 4.3 Belt width necessary for a given lump size. Fines: no grater than 1/10 maximum lump size. 47 Area of load cross section. 49 Flat belt loading. 51 Belt Conveyor Idlers Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4 Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 5.12 Figure 5.13 Figure 5.14 Figure 5.15 Figure 5.16 Figure 5.17 35° troughing idler. 57 Flat belt idler. 57 Return belt idler. 57 20° troughing idler. 58 35° offset troughing idler. 58 20° picking belt idler. 59 35° troughing rubber-cushion impact idler. 59 Flat-belt rubber-cushion impact idler with fixed shaft. 60 35° troughed belt training idler. 60 Suspended or garland idlers. 61 Return belt idler. 62 Rubber-disc return idler. 62 Helical or spiral self-cleaning return idler. 62 Return training idler. 63 Two-roll “Vee” return idler, rigid design. 63 Two-roll suspended “Vee” return idler. 63 K2 = Effect of load on predicted bearing L10 life. 73 Figure 5.18 K3A = Effect of belt speed on predicted bearing L10 life. 73 Figure 5.19 K3B = Effect of roll diameter on predicted bearing L10 life (based on same belt speed). 74 K4A = Effect of maintenance on potential idler life. 75 K4B = Effect of environmental conditions of potential idler life. 75 K4C = Effect of operating temperature on potential idler life. 75 Figure 5.20 Figure 5.21 Figure 5.22 xvi Discharge over end pulley to form conical pile. 25 Capacities, Belt Widths, and Speeds Figure 4.1 CHAPTER 5 Traveling winged stacker with slewing boom stockpiles on both sides of the feed conveyor. 23 Bucket wheel of this combination stacker-reclaimer discharges onto the stacker boom conveyor, which is reversed for the reclaim operation. 24 Bucket wheel reclaimer with wheel at end of boom. 24 Crawler-mounted bucket wheel reclaimer with wheel mounted on chassis discharges onto a rail-mounted reclaim conveyor with slewing boom. 25 List of Figures CHAPTER 6 Belt Tension, Power, and Drive Engineering Figure 6.1 Variation of temperature correction factor, Kt, with temperature. 89 Figure 6.2 Effect of belt tension on resistance of material to flexure over idler rolls. 94 Effective tension required to accelerate material as it is fed onto a belt conveyor. 99 Inclined or horizontal conveyor, pulley driving belt. 104 Declined conveyor. Lowering load with regeneration, belt driving pulley. 104 Single-pulley/drive arrangements. 110 Single-pulley drive at head end of conveyor without snub pulley. 110 Single-pulley drive at head end of conveyor with snub pulley. 110 Single-pulley drive at tail end without snub pulley. Used when head end drive cannot be applied. 110 Single-pulley drive at tail end of conveyor without snub pulley; regenerative. 110 Single-pulley drive at tail end of conveyor with snub pulley; regenerative. 110 Single-pulley drive at head end of conveyor without snub pulley; regenerative. 111 Single-pulley drive at head end of conveyor with snub pulley; regenerative. 111 Single-pulley drive on return run. 111 Single-pulley drive on return run; regenerative. 111 Dual-pulley drive arrangements. 112 Dual-pulley drive on return run. 112 Dual-pulley drive on return run; regenerative. 112 Dual-pulley drive on return run; regenerative. 112 Dual-pulley drive on return run. Drive pulleys engage clean side of belt. 112 Dual-pulley drive with primary drive on tail pulley of conveyor; regenerative. 112 Dual-pulley drive with primary drive on head pulley ...
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