- What about CFM? Cubic Foot per Minute is not as important as the ultimate vacuum. Low CFM only means that it takes longer to remove air from your layup. Typically 3CFM and higher will do. -Evan
As Tim Allen would say, “R R R!” There’s nothing wrong with more power. Better to have too much than not enough.
I got an older GAST pump that I originally planned on using for vacuum bagging but I’ve been considering doing some infusion with it. It pulls 26" and flows 4.5 CFM…would this be able to handle infusion?
Nope…too much air still in the bag @ 26"/hg
Okay guys, please forgive me, can someone explain what all that stuff means. What is 26" of pull, vs CFM’s? What’s with all the #'s? Or can you point me to a site where I can learn what’s what?
“Inches of Mercury” is a method for measuring vacuum
Say you have 26.0"/hg…that equals only a 87% Vacuum. That means you still have 13% of the volume as being taken up with Air molecules (ie. that is enough to REALLY screw up an infusion molding)
CFM (Cubic Feet per Minute) is a term for measuring the amount of air flow that a compressor can do. There are 2 basic types…Actual CFM and Displacement CFM
Actual CFM is waht you can actually measure coming out of the compressor in a regular atmosphere. This number changes with air pressure and motor RPM and air line resistance.
Displacement CFM is the volume that the Piston displaces over a full minute. It more theorectical than anything and only changes with motor RPM
Robinair pumps are measured in Microns becasue they can go that far to a deep vacuum. Gast pumps cant go anywhere near there…so they are measured with Inches of Mercury (probably to make them look more impressive by marketers…would you buy something that did a 29"/hg or a 20,000 Micron vacuum 
)
Here is a chart to help you see the corelations between all the vacuum scales that are dealt with here.
Great post, Evan put a sticker on that 1!
I can’t claim responsibility for that chart. 
hehe…I just borrowed it from Nandor pumps I keep it always on hand though when I’m looking at pump specs
Thanks Spruce, That is a great post and hopefully I can find something within my $ range.
what the hell does this mean then???
has a vacuum pressure into the 10 to the minus 3 millibar zone
i reckon this should do the trick :lol:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=3868037607&ssPageName=STRK:MEWA:IT
10^-3 millibar = 0.001 millibar = 0.000001 bar
10,000 microns then or 29.5ish mercury,not bad.
Huh? If it is 1x10^-3 millibar, thats about 1 microns.
That Edwards pump you linked, it just said 9.8 x 10^-3, but no units. Without units it’s meaningless. Is it 9.8x10^-3 millibars, which would be closer to 10 microns. Or is it 9.8x10^-3 bars or close to 7600 microns. Or is it absolute pressure in psi or inches of mercury or inches of water… etc, I think you get the idea now.
now youve really confused me :?
I’d buy it if it stays at that price.
Search the 'net for Edwards E1M-18
“Purchased in year 2000 and used in racing car factory for composite production. Without the trolley and ancileries these pumps cost in the region of £2500.”
Shows a guage reading of 29.5"ish.
I looked up the specs for the Edwards E2M18 vacuum pump. It is rated at 1x10^-3 mbar. Which is 0.001 mbar = 0.000001 bar. 1 bar = 1 atm. So this is a 1 microns vacuum pump.
All this stuff is metric, which you are suppose to be familiar with on the other side of the pond. The inches of mercury and psi is an American thing. Looks like someone was day dreaming in class during the lecture on metric units.
:oops: heh heh,i was more into the practical lessons :lol:
well i bought this one-
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=3867206833&ssPageName=STRK:MEWN:IT
i havent recieved it yet,the guy couldnt read the label as its damaged so im not sure which model it is? i reckon i should be able to make a hose and regulator up with all the bits that come with it…
That will work. Ask him if he knows a source for vacuum pump oil for the unit. I would change the oil on a used unit as a 1st step.