valutazioni - 3, GPA: 4
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Main line size labeled on sketch. ............................................................................ Figure 50. Branch line sizes labeled on sketch. Total CFM Branch Line Size 600 5" 700 5" 800 6" 1000 6" 1200 7" 1400 8" 1600 8" Figure 51. Branch line sizing chart by total CFM (for use when multiple machines share line). OPERATIONS -33 W1808/W1809/W1810 Cyclone Dust Collectors OPERATIONS Calculating Duct Resistance Adding duct work, elbows, branches and any other components to a duct line increases airflow resistance (static pressure loss). This resistance can be minimized by using rigid (smooth) pipe and gradual curves, as opposed to flexible pipe and 90. elbows. To help you think about this resistance, imagine riding a bicycle in a tunnel that is an exact replica of your duct work. If the inside of the tunnel is very bumpy (flexible pipe) and has a lot of sharp turns (90. elbows), it will take a lot more effort to travel from one end to the other. The purpose of calculating the resistance is to determine if it is low enough from the machine to the dust collector to meet the given CFM requirement for the machine. Use the charts in Figure 52 to calculate the resistance of duct work. In most small/medium shops it is only necessary to calculate the line with the longest duct length or the most fittings (operating under the assumption that if the line with the highest resistance works, the others will be fine). To calculate the static pressure of any given line in the system, do these steps: 1. Make a list of each size duct in the line, including the length, and multiply those numbers by the static pressure value given in Figure 52. 2. List each type of elbow or branch and multiply the quantity (if more than one) by the static pressure loss given in Figure 52. 3. Add the additional factors from Figure 53 to your list. Duct Approximate Approximate Dia. Static Pressure Static Pressure Loss Per Foot of Loss Per Foot Rigid Pipe of Flex Pipe Main Branch Main Branch Lines Lines Lines Lines at 3500 at at at 4000 FPM 4000 3500 FPM FPM FPM 2" .091 .122 .35 .453 2.5" .08 .107 .306 .397 3" .071 .094 .271 .352 4" .057 .075 .215 .28 5" .046 .059 .172 .225 6" .037 .047 .136 .18 7" .029 .036 .106 .141 8" .023 .027 .08 .108 9" .017 .019 .057 .079 Fitting Dia. 3" 4" 5" 6" 7" 8" 90. Elbow .47 .45 .531 .564 .468 .405 45. 45. 90. Elbow Wye(Y) Wye(Y) .235 .282 .188 .225 .375 .225 .266 .354 .236 .282 .329 .235 .234 .324 .216 .203 .297 .189 Figure 52. Static pressure loss charts. Additional Factors Static Pressure Seasoned (well used) Dust Collection Filter 1" Entry Loss at Large Machine Hood 2" Figure 53. Additional factors affecting static pressure. -34 W1808/W1809/W1810 Cyclone Dust Collectors 4. Total your list, as shown in the example in Figure 54, to come up with your overall static pressure loss number for that line. Note: Always account for a seasoned filter, so you don't end up with a system that only works well when the filter is clean. Note: When calculating static pressure loss to determine if multiple lines can be left open at the same time, only include the main line numbers once. 5. Compare the total static pressure loss for that line to the closest CFM given in the Performance Curve section on the machine specifications for your dust collector (located toward the front of this manual). — If the CFM for your static pressure loss is above the requirement of the machine connected to the end of that branch line, then dust collection will most likely be successful. Congratulations! You've just designed your own dust system. Refer to Page 37 to start buying the components necessary to make your system a reality. — If the CFM for your static pressure loss is below the requirement of the machine, then that line will not effectively collect the dust. You must then modify some of the factors in that line to reduce the static pressure loss. Some of the ways to do this include: 1) Installing larger duct, 2) reducing amount of flexible duct used, 3) increasing machine dust port size, 4) moving machine closer to dust collector to eliminate duct length, and 5) reducing 90. elbows or replacing them with 45. elbows. .................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... Figure 54. Example list for totaling static pressure loss. OPERATIONS -35 W1808/W1...
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