Dust Control Handbook for Industrial Minerals Mining and Processing

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CarrybackMaterial that sticks or clings to a conveyor belt after passing over the head pulley is calledcarryback. Carryback tends to fall from the belt as it passes over return idlers. This creates pilesof material that require clean-up, which can increase worker dust exposure. Also, respirableportions of carryback can become airborne and increase fugitive dust exposure levels. The goalis to remove carryback before it is released into the air and becomes a source of contamination tothe workers or creates piles of material that require clean-up.The primary means of controlling carryback is to clean the belt as it passes over or past the headpulley (i.e. shortly after material is discharged from the belt). The two most common means ofcleaning a conveyor belt of carryback are to mechanically "scrape" the belt via scrapers orbrushes or to wash the belt.Belt ScrapersThere are a myriad of different types and configurations of scrapers and addressing them all isbeyond the scope of this handbook. Instead, the basic principles and types of scrapers will beaddressed. Although belt cleaner systems come in many different styles, types, and trade namessold by numerous commercial manufacturers, their function remains the same: to reduce theamount of carryback on the belt once the ore is discharged.Material can be either scraped or peeled from a belt. When material is scraped from a belt, thescraper is angled with the direction of belt travel (Figure 5.12).Figure 5.12. Typical method for scraping material from a belt.Multiple scraper belt cleaner systems provide a way to address carryback, with the use of aprecleaner on the face of the head pulley to remove most of the material, followed by secondarycleaners to perform final cleaning. The secondary scrapers can be installed either where the beltleaves the head pulley or further along the conveyor return. To be effective as well as to reducebelt wear, multiple cleaners should be incorporated with low blade-to-belt pressure [Goldbeckand Marti 2010]. When dust levels are high, it is not uncommon to use two or three belt scrapersConveying and Transport 141
at different locations in an effort to further reduce the amount of carryback material on the belt[Roberts et al. 1987].It is most desirable to return the scrapings to the primary material flow through chutes(Figure 5.13). Chutes should therefore be designed large enough to capture the scrapings andtheir walls steep enough to prevent scrapings from building and stacking up within the chute.Figure 5.13. Belt conveyor discharge chute used to return scrapings to the primary material flow.Belt WashingSome studies have shown that oversized material is more easily removed through scraping, butthat the smaller respirable size particles tend to remain adhered to the conveyor. Washing is analternative when belt scraping does not remove particles adhering to the belt. A belt washsystem sprays the conveyor belt with water while simultaneously scraping it to remove theproduct. A handbook from Martin Engineering, Foundations: The Practical Resource forCleaner, Safer, More Productive Dust & Material Control [Swinderman et al. 2009], devotes achapter to a thorough discussion of belt washing systems.142 Conveying and Transport
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Report of Investigations 9689Dust C
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FUNDAMENTALS OF DUSTCOLLECTION SYST
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Minimizing Field Fits and Welds ...
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Recommendations for Proper Wet Dril
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CONTROL TECHNOLOGIES FOR FILLING 50
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Effective Filtration ..............
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ILLUSTRATIONSFigure 1.1. Relationsh
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Figure 3.2. The air and water flow
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Figure 9.5. Problem created by heat
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UNIT OF MEASURE ABBREVIATIONSUSED I
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Robert J. Franta, Quotation Enginee
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silica. Quartz is the most common s
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DUST CONTROL HANDBOOK FOR INDUSTRIA
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CHAPTER 1: FUNDAMENTALS OFDUST COLL
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The shape of particles affects how
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EXHAUST SYSTEMS DESIGNAll exhaust s
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stripping, which allows workers to
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When using the air quantities in Ta
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X = distance in feet from the face
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Checklist for Hood EffectivenessThe
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A major disadvantage of the high-ve
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A common misconception when designi
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Avoiding Mitered Elbows Greater Tha
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Figure 1.13. Depiction of the horiz
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Figure 1.14. Typical design of grav
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Baghouse CollectorsBaghouse dust co
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Table 1.2. Emission factors for cru
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Figure 1.17. Typical design of a me
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Reverse Jet (Pulse Jet) CollectorsR
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Figure 1.20. Cartridge collector wi
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Wet scrubbers are particularly adva
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Electrostatic precipitators normall
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may be related to specific applicat
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times. When considering the depth o
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Figure 1.25. Demonstration of how a
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Figure 1.26. A typical fan performa
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Fan TypesThere are two basic types
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Figure 1.30. Typical centrifugal fa
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Figure 1.32. Typical roof ventilato
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The vast majority of dust particles
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Table 2.1. Particle/droplet size in
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Air Atomizing NozzlesAir atomizing
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Hydraulic Flat Fan NozzlesFigure 2.
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for dust knockdown or suppression,
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Nozzle MaintenanceFigure 2.14. Typi
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Accidental DamageInadvertent harm t
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NDT Educational Resource Center, Io
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78 Wet Spray SystemsDUST CONTROL HA
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contains a piston which delivers ha
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produce an increase in the penetrat
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Dry DrillingDry drilling is accompl
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Circular ShroudIn contrast to the u
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The collector airflow has a more su
Page 119 and 120: Air-Blocking ShelfThe air-blocking
Page 121 and 122: dust emissions from mast lowering,
Page 123 and 124: This simple procedure of creating a
Page 125 and 126: Figure 3.15. Air ring seal used to
Page 127 and 128: Figure 3.17. Illustrations showing
Page 129 and 130: unsubstantiated due to the inconsis
Page 131 and 132: safety considerations may preclude
Page 133 and 134: Figure 3.22. A filtration unit, loc
Page 135 and 136: Miller S, Emerick JC, Vogely WA [19
Page 137 and 138: USBM [1995]. The reduction of airbo
Page 139 and 140: 110 Drilling and BlastingDUST CONTR
Page 141 and 142: Wet Control MethodsPREVENTION AND S
Page 143 and 144: Figure 4.2. Examples of compressive
Page 145 and 146: Figure 4.5. Illustration of a dry (
Page 147 and 148: Figure 4.6. Illustration of a dry (
Page 149 and 150: Wet dust control methods for crushi
Page 151 and 152: Work Practices to Minimize Dust Exp
Page 153 and 154: Some specialty grinding operations
Page 155 and 156: should be frequently inspected for
Page 157 and 158: Open screen decks slowly to allow i
Page 160 and 161: DUST CONTROL HANDBOOK FOR INDUSTRIA
Page 162 and 163: CHAPTER 5: CONVEYING AND TRANSPORTT
Page 164 and 165: Figure 5.3. Basic depiction of mate
Page 166 and 167: that the material falls before land
Page 168 and 169: Figure 5.10. Skirtboard used within
Page 172 and 173: CONVEYOR DESIGN AND MAINTENANCE ISS
Page 174 and 175: Figure 5.15. Conveyor transfer encl
Page 176 and 177: High-volume, high-pressure sprays s
Page 178 and 179: Figure 5.19. Depiction of a bucket
Page 180 and 181: Figure 5.21. Depiction of two types
Page 182 and 183: Figure 5.25. Venturi eductor utiliz
Page 186 and 187: CHAPTER 6: BAGGINGThis chapter disc
Page 188 and 189: caused during manufacturing, includ
Page 190 and 191: Overall PerforationsThe use of over
Page 192 and 193: Figure 6.5. Open-top bag being load
Page 194 and 195: Bagging operators should be aware t
Page 196 and 197: Figure 6.8. Exhaust hood to capture
Page 198 and 199: In the original design, a single no
Page 200 and 201: The OASIS is a relatively simple de
Page 202 and 203: Figure 6.13. Bag storage shelves sh
Page 204 and 205: Figure 6.14. Bag and belt cleaner d
Page 206 and 207: other industrial application using
Page 208 and 209: The robotic arm automatic palletize
Page 210 and 211: For many years, this plastic wrappi
Page 212 and 213: warehouse location until a later ti
Page 214 and 215: used successfully to perform this c
Page 218 and 219: CHAPTER 7: BULK LOADINGDuring the b
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Figure 7.2. Loading spout discharge
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Cascading Loading SpoutFigure 7.5 i
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a seal at the entry and exit points
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REFERENCESBiere G, Swinderman RT, M
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200 Bulk LoadingDUST CONTROL HANDBO
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many years, as well as some new and
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Figure 8.2. Air spray manifold desi
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Figure 8.3. Test subject wearing po
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Spills of product material are a co
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epetitive dust leaks should not sim
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Effective Upward Airflow PatternThe
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Figure 8.8. Open-structure design c
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manually removing the bags and plac
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Figure 8.12. Increase in worker’s
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In other cases, an operation may wa
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Cecala AB, O'Brien AD, Pollock DE,
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224 Controls for Secondary SourcesD
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where C o = outside respirable dust
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minimal improvement in the cab's ai
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RECOMMENDATIONS FOR FILTRATION/PRES
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Effective FiltrationFigure 9.4. Res
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average decay times were between 16
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Figure 9.6. Filtration unit showing
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This table highlights a number of c
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NIOSH [2001b]. Technology news 486:
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upon the wind velocity (or disturba
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Maximum size is the largest particl
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Figure 10.4. Use of end-dumping wit
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conditions. Performance of each of
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A water truck, used to apply water
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Surfactants work by reducing the su
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which differed for the various site
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Figure 10.9. Self-tarping dump truc
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percent [Fryrear and Skidmore 1985]
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Figure 10.12. The armoring process
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A current method of stockpile forma
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Figure 10.15. Demonstration of how
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Chekan GJ, Cecala AB, Colinet JF [2
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Midwest Research Institute [1981].
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GLOSSARYAbrader. An implement used
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Carryback. Material that sticks or
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End-dumping. A process of spreading
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Open structure building design. A p
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Table bushing. A bushing used to se
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Delivering on the Nation’s promis
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