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Dust Collection The importance of dust collection & choos- ing the right type of duct for dust collection

Why you need a dust collection system vs. Plastic Duct” below.) The next step is to size your system. (See “Designing Your System” on Installing an effi cient dust collection system pages 41-44.) should be a priority for the small shop as well as the large shop, whether the material being Metal vs. Plastic Duct machined is wood, plastic, or a composite. Not only is this essential for health reasons and Plastic pipe (or PVC pipe) is unsuitable for compliance with many national and local codes, dust collection for three reasons: but it is also good business because it saves • First, plastic pipe fi ttings are not offered money and helps to maintain the quality of the in the diversity required to meet design fi nished product. requirements. The harmful health effects of inhaled • Second, plastic pipe elbows have a particulates (many of which are carcinogens) short radius, which encourages clogs and are well documented, and skin, eye, and compromises system effi ciency. nose problems as well as allergic reactions • Third, and most important, plastic pipe are frequently reported. In addition, a dusty is non-conductive and builds up a static shop increases the risk of worker injury and charge as charged particles pass through fi re, which can result in lost production, higher it. This static charge can discharge at any insurance rates, and lawsuits. time causing shock and surprise, which A dusty shop compromises the quality of the is dangerous around running machinery. fi nished product: Accurate measurements and More serious is the risk of explosion and cuts are more diffi cult due to lack of visibility; fi re. Fine dust particles suspended in air airborne dust fi nds its way into fi nishing areas have signifi cant explosion potential—all causing defects in the fi nal product; and larger particles cling to surfaces cause scoring and that is needed is a spark, which the static other defects. charge on plastic pipe conveniently supplies. Grounding plastic pipe requires wrapping it Finally, dust that is not automatically collected in wire both inside and out—an expensive must be collected manually as a recurring direct labor expense. (and never certain) proposition that negates the minimal price savings in going to plastic By any measure, an effi cient dust collection in the fi rst place. system is an investment that more than pays for itself. Spiral steel pipe has none of these disadvantages. An incredible variety of Designing a dust collection system fi ttings are available and custom fi ttings In the simplest terms, a dust collection system can be easily fabricated. The fi ttings are is comprised of a ducting system to transport designed with long radius to minimize the dust from the source (table saw, planer, clogging, and special fi ttings such as clean- etc.) and a collection device (such as a bag and outs and quick disconnects are available. fi lter system or a cyclone), which pulls the dust Most important, Spiral metal pipe is through the ducting and collects it. The very conductive, and simple and easy to ground, fi rst decision you must make is whether your even when fl exible rubber hose is used to ducting will be metal or plastic—and here there connect the duct to the machine. is only one logical choice: metal. (See “Metal

11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158 39 Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184 Standard dust collection components Dust Collection & accessories

Spiral Manufacturing has all the duct components you need to design and build a safe and effi cient dust collection system

Laterals (Pages 12-14) Reducers (Page 15) Elbows (Pages 5-6)

Blast Gates (Pages 31-32) Clean-outs (Page 30) Floor Sweeps (Page 17)

Clear Flex Hose (Page 33) Manifolds (Page 14) Custom Hoods (Page19)

Clamps (Page 34) Bellmouth (Page 17) Duct Sealants (Page 27)

40 www.spiralmfg.com

Dust Collection How to design an effi cient dust collection system with Spiral pipe.

Designing Your System Step 2 There are two phases to designing your dust collection system: Determine the diameter of each branch line. You can use the The fi rst phase is sizing your duct work for adequate volume and diameter of a factory installed collar or port, or consult the velocity of fl ow for the type of dust you will be creating; and the manufacturer. Convert metric ports to the nearest inch. Convert second phase is computing the static pressure (SP) of your system rectangular ports to the equivalent round diameter. Ports less than to determine the size and power of your dust collection unit. 3” will require a reducer to 4”. Record any reducers or rectangular Prior to making your calculations, diagram the fl oor plan of your to round transitions on your take off list. shop to scale on graph paper. Include the size and location of each Step 3 machine, and the location of its dust port or outlet; the fl oor to joist dimension; the location of the dust collecting unit; and the most Using Table 41-2, determine the CFM requirement of each branch. effi cient (fewest number of turns or bends) path for routing your Remember the FPM for wood dust in branch lines is 4500. duct lines. This is also a good time to start your take-off list of duct Example: Table saw 4” dia. 390 CFM (rounded) components for your system. Planer 5” dia. 610 CFM (rounded) You will also need to familiarize yourself with the following Lathe 6” dia. 880 CFM (rounded) concepts: Continue for all branches. CFM (Cubic Feet per Minute) is the volume of air moved per minute. Table 41-2: CFM for for pipe diameter at specifi ed velocity FPM (Feet per Minute) is the velocity of the airstream. SP (Static Pressure) is defi ned as the pressure in the duct that tends Diameter 3500 FPM 4000 FPM 4500 FPM to burst or collapse the duct and is expressed in inches of water 3” 277 316 356 gage (˝wg). VP (Velocity Pressure), expressed in inches of water gage (˝wg), is 4” 305 348 392 the pressure in the direction of fl ow required to move air at rest to 5” 477 546 614 a given velocity. 6” 686 784 882 CFM is related to FPM by the formula CFM = FPM x cross-sectional area (ft2). FPM is important because a minimum FPM is required 7” 935 1068 1202 to keep particles entrained in the air stream. Below this minmum 8” 1222 1396 1570 FPM, particles will begin to settle out of the air stream, forming clogs—especially in vertical runs. Table 41-1 shows the minimum 9” 1546 1767 1988 FPM that Spiral Manufacturing recommends for several types of 10” 1909 2182 2455 dust in branch and main runs. 12” 2749 3142 3534 Step 1 From the Table 41-1 determine the velocity (FPM) of your system 14” 3742 4276 4810 for the type of dust that will be produced. For the purpose of For larger diameters see pages 59-60. the following examples assume woodworking dust. Wood dust Step 4 requires 4500 FPM in branches and 4000 FPM in mains. Identify your primary or high-use machines. These are the machines that operate simultaneously on a frequent basis. The objective here Table 41-1: Velocity for Type of Dust is to defi ne your heaviest use scenario so you can size your system Velocity Velocity to meet it. Including infrequently used machines and fl oor pick- Type of Dust in Branches in Main ups in your calculations will only result in an over-designed system (FPM) (FPM) that will cost more to purchase and to operate. At this point, all of Metalworking Dust 5000 4500 your branch lines are sized, and you have a list of all components required for your branch lines. Woodworking Dust 4500 4000 Step 5 Plastic/Other Now you are ready to size the main trunk line. Begin with the Light Dust 4500 4000 primary machine that is furthest from where you will place the dust

Figure 41-1 Floor Pick-Up Planer Lathe (Primary) (Primary) Dust 45° Reducing Lateral Collector 90° Elbow 5˝Ø 10‘ 8‘ 15‘ 12‘

4˝Ø 7˝Ø 10˝Ø 10˝Ø Table Saw 6‘ Radial Arm Saw (Primary) 45° Standard Lateral 45° Elbow Sander 6‘ Floor Pick-Up

11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158 41 Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184 How to design an effi cient dust collection Dust Collection system with spiral pipe.

collecting unit. In our example, this is the table saw, which has a Figure 42-2 branch diameter of 4”. Run this 4˝ Spiral pipe to the point where 2) Calculate the SP of the main: the second primary machine (the planer on a 5˝ branch) will enter the main. (Note: If a non-primary machine or pick-up is added to In our example the main has one 8’ run of 7” Spiral pipe, two the system between primary machines, the size of the run is not runs (15’ and 12’) of 10” Spiral pipe connecting the main to increased.) the dust collector. In addition, there are 5 lateral reducers in the main. Our calculations for 4000 FPM in the main are as You now have a 390 CFM line (table saw) and a 610 CFM line follows: (planer) combining for a total of 1000 CFM. Using Table 41-2 again, you will see that for 4000 FPM (the velocity requirement for SP (˝wg) main line that you determined in Step 1) the required pipe diameter Eight feet of 7˝ Spiral pipe: falls between 6” and 7”. (Note: Spiral Manufacturung recommends Table 55-2 shows 3.55 ÷ 100 x 8 = 0.28 that you round up to 7”. This not only assures adequate air fl ow Twenty-seven feet (15 + 12) of 10˝ pipe: but also anticipates a future upgrade in machine size.) Table 55-2 shows 2.30 ÷ 100 x 27 = 0.62 Now calculate for the addition of the third primary machine (the lathe on a 6˝ branch). You have an 1000 CFM main + an 880 CFM Total SP loss (˝wg) for the main run: .90 branch line (for the lathe) for a total of 1880 CFM. Using Table Figure 42-3 41-2 once again, 1880 CFM at 4000 FPM requires between a 9” 3) Calculate the SP for the collection units fi lter and and 10” pipe. We recommed rounding up to a 10” main after seperator: the addition of the lathe. The main going to your dust collecting For these calculations, consult with the manufacturer of the unit will be 10”, and your dust collection unit must be capable of collection units you are considering. For this example, we will pulling 1880 CFM through a 10” duct at 4000 FPM. assume that there is no pre-separator an that the SP for the fi lter is 1.5. Step 6 Total SP for fi lter: 1.50 In this step, you calculate the Static Pressure (SP) or the resistance of your system that your dust collection unit must Summing the SP loss for the system, we have: overcome. Static Pressure is measured in inches of water gage 1) Highest loss branch: 5.17 (˝wg). To do this you total the Static Pressures of the following 2) Loss for main: .90 3) Filter loss: 1.50 system component groups: 1) The branch line with the greatest SP or resistance (see Figure Total SP loss (˝wg) loss in the system): 7.57 42-1). Calculate the SP of all branchs to determine which has the You now have the information you need to specify your dust col- greatest SP. Only the branch with the greatest SP or resistance is lector. Your dust collection unit must provide a mimimum of added to the total. 1880 CFM through a 10” duct at 4000 FPM, and have a static 2) The SP of the main run (see Figure 42-2). pressure capability of no less than 7.57 (˝wg). 3) The SP for the collection unit’s fi lter, if any, and for the pre- separator, if any (see Figure 42-3). Additional Considerations and Recommendations: (You can use the charts on pages 51-60 to assist in your The above example is for a small system with few variables. It calculations.) is recommended that for larger systems a professional engineer be consulted to assure that the system is properly designed and Figure 42-1 sized. If the dust collector is located in a seperate enclosure, it is 1) Calculate the SP of the branch with the greatest SP: essential to provide a source of make-up air to the shop to (4 feet of fl ex hose and one 90° elbow not shown) prevent a down draft through the fl ue of the heating system. Starting at the machine and working toward the main, If this is not done, carbon monoxide poisoning could result. If a determine the SP of each branch line component, and then return duct is necessary from the dust collector, it should be sized total them. In our example, the branch with the greatest loss is two inches larger than the main duct entrance and its SP loss the table saw branch, and it calculates out as follows using an added into your calcualtions. FPM of 4500 for branch lines: Some dust collection units may not include fan curve information SP (˝wg) that shows CFM or Static Pressure variables. We do not recom- mend procuring collector equipment without this information. Entry loss at machine adaptor collar is 1.5 SP (a constant) = 1.5 Blast gates should be installed on all branch lines to maintain Four feet of 4˝ fl ex-hose*: system balance. Chart 57-1 shows 4˝ fl ex-hose (at 390 CFM) = Dust suspended in air has a potential for explosion, so it is recom- .8 SP ÷ 100 x 4 x 27.7 = .886 SP (˝wg) = 0.886 mended that you ground all of your duct runs, including fl ex-hose. Three 4˝ 90° elbows: If your system has areas where long slivers of material could pos- Chart 51-1 shows one elbow = .28 SP loss (˝wg) x 3 = 0.84 sibly hang-up and cause a clog, install a clean-out near that area. Three branch runs of 4˝ pipe (6+6+10) = 22’: Table 55-2 shows 8.8 ÷ 100 x 22’ = 1.94 Many types of dust, including many woods are toxic, so take special care to choose a fi ltering system that will provide optimal Total SP loss (˝wg) for the table saw branch equals: 5.17 safety.

* Flex-hose should be wire wrapped helix hose to permit grounding. See photo on page 33.

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Dust Collection Exhaust Volumes & Conveying Velocities for a Variety of Production Machines

This list of recommended exhaust volumes and pipe such a high speed that their trajectories cannot be altered sizes for average sized metal working and woodworking by a vacuum system regardless of its velocity. In addition machines is based on many years of experience and the hoods should be placed as close to the source of dust work of many people. Some modern high speed or extra contamination as possible since the effectiveness of an large machines will require higher velocities than shown. exhaust hood decreases very rapidly as it is moved away Smaller machines may use less air than shown. The air vol- from the source. The following recommended pipe sizes ume required to capture the dust at the machine will vary are based on the use of reasonably good hoods. with each operation. Particle size and hood type must be considered. The following charts will provide an excellent Wide belt and abrasive sanders, moulders and shapers guide to determine your total air volume requirements. with high R.P.M. spindles often call for higher duct velocity (through hoods supplied by manufacturers) than those indi- Caution: One of the most important factors in an effi cient cated on the charts. In these cases caution must be used. dust collection system is proper hood design. Hoods must be designed so that the dispersed particles are thrown or The following charts are recommended for machines with defl ected directly into the hood opening. The large heavy good hood enclosures. (Also check with the machine particles thrown out by the cutting heads or wheels have manufacturer for their recommended velocities.)

Table 43-1: Recommended Conveying Velocities for Various Production Machines >˜}Ê,ˆ«Ê->ÜÃÊ œˆ˜ÌiÀ ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ /œÌ>Ê >`i ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ ˜ˆviÊ7ˆ`Ì ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ ˆ>°Ê­ˆ˜°® ­ˆ˜°®  ˆ>°  ˆ>°  ˆ>° 1«Ê̜ÊÈ¿¿ Ιä {¿¿ 1«Ê̜ÊÓ{¿¿Êˆ˜V° È£ä x¿¿ Ιä {¿¿ Ç¿¿Ê̜Ên¿¿ È£ä x¿¿ Óx¿¿Ê̜ÊÎÈʈ˜V° nnä È¿¿ È£ä x¿¿ n¿¿Ê̜ʣn¿¿ nnä È¿¿ ÎÈ¿¿Ê̜Ê{n¿¿Êˆ˜V° £Óää Ç¿¿ È£ä x¿¿ "ÛiÀÊ{n¿¿Êˆ˜V° £xÇä n¿¿ nnä È¿¿ ˆÃVÊ->˜`iÀ /ÕÀ˜ˆ˜}Ê>Ì ià ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ ˆÃV ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ /ÕÀ˜ˆ˜}Êi˜}Ì ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ ˆ>°Ê­ˆ˜°® ­ˆ˜°®  ˆ>°  ˆ>° 1«ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ̜ʣӿ¿ Ιä {¿¿ 1«Ê̜ʣӿ¿ nnä È¿¿ £Î¿¿Ê̜ʣn¿¿ È£ä x¿¿ £Î¿¿Ê̜ÊÓ{¿¿ £xÇä n¿¿ £™¿¿Ê̜ÊÎÓ¿¿ nnä È¿¿ Óx¿¿Ê̜ÊÎÈ¿¿ £™nx ™¿¿ Îο¿Ê̜ÊÎn¿¿ £Óää Ç¿¿ ÎÇ¿¿Ê̜Ê{n¿¿ Ó{xä £ä¿¿ Ι¿¿Ê̜Ê{n¿¿ £xÇä n¿¿ œœÀÊ-Üii« œÀˆâœ˜Ì>Ê iÌÊ->˜`iÀ ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ -ˆâi ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ iÌÊ7ˆ`Ì ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ ­ˆ˜°®  ˆ>° x¿¿ È£ä x¿¿  ˆ>°  ˆ>° È¿¿ nnä È¿¿ 1«Ê̜ÊÈ¿¿ nnä È¿¿ È£ä x¿¿ Ç¿¿ £Óää Ç¿¿ Ç¿¿Ê̜ʙ¿¿ £Óää Ç¿¿ nnä È¿¿ œœÀÊ -Üii«ÃÊ >ÀiÊ ˜œÌÊ >``i`Ê ÌœÊ Ì iÊ ÌœÌ>Ê œ>`Ê œvÊ Ì i £ä¿¿Ê̜ʣ{¿¿ £™nx ™¿¿ £Óää Ç¿¿ iÝ >ÕÃÌiÀÊ>ÃÊÌ iÞÊ>Àiʈ˜Êœ«iÀ>̈œ˜Êœ˜ÞÊ>ÊviÜʓˆ˜ÕÌiÃÊ>ÌÊ> ̈“i° "ÛiÀÊ£{¿¿ Ó{xä £ä¿¿ £Óää Ç¿¿ ­ œÕÌ ÊœvÊvœœÀÊÃÜii«Ê£ä¿¿ÊÝÊ{¿¿Ê̜ʣӿ¿ÊÝÊ{» >««ÀœÝ°® -ˆ˜}iÊ-ÕÀv>ViÀ ˆÀVՏ>ÀÊ->Ü ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° ,iVœ““i˜`i`Ê6iœVˆÌÞÊ{]ÓääÊ̜Êx]äääÊ°*° ° Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ Ý >ÕÃÌÊ6œÕ“iÃÊ>˜`Ê*ˆ«iÊ ˜ˆviÊ7ˆ`Ì ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ >`i ˆ>“iÌiÀÃÊ>ÌÊ{xääÊvÌ°Ê6iœVˆÌÞ ­ˆ˜°® ˆ>°Ê­ˆ˜°®  ˆ>°  ˆ>° 1«Ê̜ÊÈ¿¿Ê܈`i Ιä {¿¿ 1«Ê̜ʣ俿 Ιä {¿¿ Ç¿¿Ê̜ʣӿ¿Ê܈`i È£ä x¿¿ £Ó¿¿Ê̜ʣ{¿¿ È£ä x¿¿ £Î¿¿Ìœ Ó俿܈`i nnä È¿¿ £È¿¿Ê̜ÊÓä¿¿ nnä È¿¿ Ó£¿¿ÌœÓÈ¿¿Üˆ`i £xÇä n¿¿ Ó{¿¿Ê̜ÊÎä¿¿ £xÇä n¿¿ ÓÇ¿¿Ìœ ÎÈ¿¿Üˆ`i £™nx ™¿¿ 6>ÀˆiÌÞÊ->ÜÃÊÜˆÌ £Óää Ç¿¿ "ÛiÀÊÎÈ¿¿Ê܈`i Ó{xä £ä¿¿ >`œÊi>`Ã

11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158 43 Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184 Exhaust Volumes & Conveying Velocities Dust Collection for Dust Producing Equipment 4,000 4,000 4,000 4,000 4,000 4,000 4,000 4,000 4,000 4,000 4,000 4,000 in FPM velocities Conveying ent to 75 to ent to at rate of 125 to 150 at rate 125 of to veyor equival Ex haust requirement Bench type, 150-250 cfm per sq. cfm 150-250 Bench type, ft. of less not grille exhaust than 150 but cfm per sq. ft. area plan working of sq.per cfm 200-400 Floor grille, ft. of less not grille exhaust than 100 but cfm per sq. ft. of plan area working and working through fpm 150 minimum inspection openings in all openings through 200 fpm less 200 cfm than not but enclosure, per sq. ft.grate area of con Ventilate sq.per 100 cfm ft.area,grate gross of assuming all at any grates open one time above Same as housing Ventilate cfm per sq. ft. gross open area.time.one Assume at open area Include all doors sides between housing and in conveyor determination.volume Usual clearance 1 in.less or each on con- veyor side are hoppers shake-out When vibrating located in a closed tunnel, ventilate the per sq.tunnel at 100 cfm ft. tunnel of cross section. Exhaust from transfer air all, re-or partof, can provide points quired.required exhaust Any additional should be taken in rear of shake-out hopper openings, hood through indraft 200 fmp less not than per 50 but sq.cfm ft. of screen area sq.per 100 cfm sec- ft.cross- circular of not less tion but than 400 in- fpm draft through openings in enclosure or inspection through indraft 100-400 fpm less not than but openings, working per sq.25 cfm ft.plan area enclosed of per 50-150 cfm sq. ft. of open face area per 95-150 cfm sq. ft. of producing dust plan area Downdraft grilles Downdraft shields Use side where possible Enclosure Enclosure None None overhead Side or hood Enclosure Enclosure Enclosure Complete enclo- sure Booth Downdraft Exhaust hood veyor veyor for producing

equipment Portable and Portable shaft flexible Foundry light flask work light flast non- castings ferrous floor-snap above flask work deck Vibrating flat Packaging, machines, granulators, en- filling inspection Dust Grinders Mixer Shake-outs Apron con Belt conveyor for Shaker con ventilation Tunnel Screens Cylindrical Miscellaneous, closed dust produc- ing units. Packaging, weighing, container

4,000 4,000 4,000 4,000 4,000 4,000 4,500 4,000 4,000 4,000 4,000 4,000 4,000 4,000 3,500 in FPM velocities Conveying requirements

Ex haust 60 - 100 fpm downdraft (long rooms of of (long rooms downdraft 100 fpm 60 - cross-draft) 100 fpm tunnel proportions less not but minute 20 air per changes all openings. through than 500 fpm be baffled Openings to tube;500feed at 500 cfm/filling cfm hopper;hopper spill at 950 cfm 100 cfm/sq.ft.min. barrel top Belt speeds less than - 200 fpm not but width, belt of foot per 350 cfm area. open through fpm 150 less than 500 - 200 Belt speeds over cfm fpm less not than but width belt of per foot area open through 200 fpm air with ft.per 350 cfm width belt of inlets every 30 ft. width.belt of Not foot per 200 cfm recommended for wet belts as in ore conveying area open feed at through 200 fpm cu. per 0.5 cfm less than not but points, ft. of bin capacity at 150-200 fpm all openings. all openings through 200 fpm 500 fpm feed, Automatic 1-5 in. dia. branch at die.in.1-5 feed, Manual dia.at branch die. 500 cfm sq.per 200 cfm ft.(Provideopening of rubber or canvas seals flexible between hopper sides shake-out and end and end) and sides also feeder and dust dry of heavyFor loads continuous dumping or feeding opera- side same as shake-out treat tions, see below hoods, cfm 200-250 occasionally, When used per sq. ft.on grate area of depending - material of dryness fineness and opening in through indraft 100-150 fpm booth face for large opening. Never 100 fpm.below with Small opening use in 200 grinder front fpm hood

Exhaust Tight enclosure with (usually air inlets in roof) Tight enclosure with access openings Booth or enclosure (provide spillage hopper) 180 deg. Local hood of barrel around top Hoods at transfer point Continuous hood max. with take-off of 30 ft.apart hood Tight fitting held against under belt side of Connect to bin top point feed from away required Tight casing Enclosure Local Complete enclosure Side hood Downdraft Booth Table 44-1: Usual Exhaust Volumes and Conveying Velocities for Dust Producing Equipment veyor producing e blast rooms e blast

equipment (sand, grit or shot) or (sand, grit cabinets (foror filling material) removing (may required with high speed belts) top) (closed bin Dry Pan Dry Press hopper shakeout to conveyor Swing frame Dust Abrasiv blast Abrasive packer Bag tube Barrels Belt conveyors Shakeout con Belt wiper Bins elevators Bucket Ceramics Vibrating feeders- Floor grate Grinder

44