Vacuum Pump Comparisons

[Gary Campbell]

I started building this Excel chart to help us decide on an upgraded vacuum source. I am posting it to possibly help some of you in your decision making. Specs come from Mfgr's.

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The Zone range blocks are from our testing; when masked off to cut a zone will flow approx 15 cfm. As we cut that flow increses to 45 cfm before we lose vacuum. 2 zone = 30 to 90 etc., This is simply a visual of the CFM that might normally be required when using that number of zones. The chart has been truncated above 220 cfm. There has been some rounding to allow data to fit.

To use the data, compare the vacuum available for the applicable number of zones, with closed on the block right (lower cfm) and cutting thru on the block left(higher cfm). The data lines of each pump combination within a zone block will give a fairly close representation of system vacuum. Vacuum on the top of the spoilboard will vary from 1.5 to 4 inHg LESS depending on the actual material used, system leaking and spoilboard condition. Margin for error 5-10%?? Your mileage may vary. Hope this helps.
Gary

[dana_swift]

Gary- that is world class work! Thanks, I will save the graphic off as a reference. I have thought about doing similar performance plots of my own system.

D

[Gary Campbell]

Dana, thanks for the generous compliment. I noticed that some might want to see data pertaining to the 9-15 parallel/series 4 motor combination. It would start on the left end at the 194 cfm point where the light blue line starts. It would be close to a straight line from that point to the zero cfm right end point of the green line. The 4 motor configuration would add a couple inches of vacuum or more from 80 cfm and up.

To me what is more intersting, once you have a given amount of cfm, is how important keeping leaks to a minimum is. Take Brady's Becker for example. The vacuum is going to the moon at 80 cfm or less, but let it leak out to 150cfm, and its only holding a couple more inches than a 9-15 parallel or twin vac motors (Fein or similar).

What I dont know is that if a higher vacuum source is applied to the spoilboard, will the flow increase? When we completely mask a zone with our plexi masks, we flow approx 15 cfm @ 6 inHg. Do the larger volume pumps pull more cfm in those same conditions? Hopefully someone with one of the "big blocks" will chime in.
Gary