Bob, It is the dust collectors job to overcome the resistance of piping, etc., and pull the total CFM required. In this case, to create a velocity of 5,905 in a 12" diameter duct, the CFM would be 4,600. The resistance must be calculated properly.How many feet of pipe, elbows, flex hose, filter loss, and so forth. Lets say the final requirement is 4,600 CFM at 11.5" SPWG. You would select the dust collector that has those coinciding figures on a performance curve or chart. In case the resistance is a bit less than calculated
and the CFM is higher than necessary, a damper can be installed to purposely induce resistance and lower the CFM delivery. The velocity and coinciding CFM for this machine is much higher than that for typical woodworking machines, but then again, this is not a typical machine. Typical conveying velocities for woodworking dust collection range from 4,000 FPM to 4,500 FPM. It is the CFM in a duct that creates the velocity in feet per minute. There is no guessing as to resistance, it must be derived at accurately. All that I have mentioned pertains to a dust collector dedicated to this machine. NFPA 664, 8.2.2.2.1.6*, Where dampers or gates are used for individual equipment, the volume and velocity resulting from the operation of such dampers or gates shall not reduce the system velocity below the design minimum. Acceptable to use them for the instance I mentioned previously. Another good air flow instrument manufacturer is Alnor.
Curt