Static Calculations

[Craig Parker]

I am doing some static calculations. Of the two best layouts, one as low airspeed (3150 FPM) and the other has high resistance (11.4"WC). I know this is because I have to use 4 elbows (long sweep) to get around obstructions and I have a Felder combination machine which needs 8' flexhose to change tools. Does anyone know if the CV 1800 is able to produce 1200 CPM and/or 12" WC? Or should I get a CV Max? Thanks.
Craig

[bababrown]

I am attaching two graphs. The first uses data published by Ed Morgano but taken by a guy in Boston. I will search to try to find his name. This data has been published as the data for the CV-1800. The 1442 CFM number still is being used as the maximum airflow. In the second graph I reduced all CFM numbers by 0.9 to reflect the average velocity rather than the peak velocity at the center of the pipe. This is the alternate approach stated by Dwyer, the pitot tube manufacturer. I have used the second graph in my install and get good correlation with my predictions. This nomograph is an easy way to predict airflow. Note that 800 CFM is about the same as 4000 FPM in 6" pipe. Add your losses taken at 4000 FPM and use the corresponding curve to predict the airflow. Ignore the total pressure curve and use just the static curve.
bababrown

[James]

Craig, Although calculations are helpful, I find that "real" results are what matters. I have over 10ft of flex hose to my Felder CF741 and about 20ft of PVC to the CV1800. I run that one line to my base cabinet and then I have another shorter 3" flex hose to the blade guard and I run 1/2 a gate to that. My Dylos counter runs at about 1,000 to 1,200 in my shop whether I'm using the Felder or milling MDF on the CNC. That is mostly because the airflow from my filters are moving residual dust from my previous inept collector. You would be happy with either the CV1800 or the MAX, but like I always encourage Felder owners to do, go BIG, you won't be disappointed. The MAX will keep your lines very clean and that extra 30% airflow will clean your whole shop faster when you let it run with an open gate for 15 or 20 minutes.

Additionally, this design will give you good fine dust separation up to around 17"wg. If there was one thing I would do different, it would be to install 7" ducting. That is really the optimum for this design.

James.

[Craig Parker]

James and bababrown,

Thanks guys. I suspect I should go with the CVMax because of the long flexhose needed for my Felder.

Craig