A one person shop - typically one machine operating at a time - I'm looking at re-installing a dust collection system following move to a new shop. The collector is an old but functioning Torit cyclone with 3hp 3-phase Baldor running at 3450rpm, 8 inch intake and 600 square foot of cartridge media (Wynn 15 merv). I have a Magnehelic attached to the exhaust plenum basically monitoring filter condition. Everything is disassembled at the moment and I'm at that stage of ordering some new pipe and then reassembling, and hoping not to make too many mistakes.
I created a spreadsheet (attached below) of the velocity issues created for the one person shop with using a range of pipe from 8" to 4". I was (sort of) shocked at the performance issues created by mixing 4" through 8" ducts. This is assuming the collector can produce 1200 to 1400 cfm at least with no friction. 4000fpm velocity in a 4" branch fed to an 8" trunk drops the velocity to 1000fpm ... enough velocity drop to "settle" dust. Keeping the velocity at 3500fpm in the 8" main trunk would require the 4" line to pull 14,000fpm of air. Neither scenario really works. Are my calculations correct? Based on this analysis, in trying to maintain trunk line velocity (3500fpm) and branch lines (4000fpm) it becomes pretty clear that the options for a single person shop include:
- keep the trunk diameters closer to the branch line diameters which means smaller than 8" (which increases static friction)
- keep branch diameter closer in size to the trunk, or not too much smaller than the trunk
- plan on keeping several gates open simultaneously (reduces efficiency at operating machine) to keep the flow of the trunk at the optimum 3500fpm
What is the best practice to maintain that 3500 fpm in the main trunk?
System Air Velocity
Read a great post started by Mathieu B. on measuring and balancing a system. I think I need to do this right now before any purchasing or assembly - the theoretical is only good to a point. I really don't know what CFM the system can optimally produce, and there is nothing like a real world test to find out. So, what is the best practice today (cheap) for measuring cfm?
Attachment 281795
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