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High flow low pressure air pump?

Billy Boy

Hot Rolled
Joined
Jan 30, 2005
Location
San Francisco, CA
I often find myself wanting a good steady stream of 10-20 psi air.

So, I run my compressor, and that is just fine for the time being, but I'm wondering if there is a device that is better suited to this kind of flow than a standard compressor which generally seem to be tuned to provide 90psi.

I've looked into some squire cage fans, but the pressure comming of them is totally inadiquate.

B
 
Venturis are widely used to generate vaccuum with live steam, encoourage flow in sanitary sewers boiler feed in steam locomotives, sand blast nozzles, etc. The nozzle design and the veneturi are usually highly optimized but the momentum exchange can be acceptable if the right conbination of plumbing fittings is used.

Scrounge the web using "venturi" or "venturi pump"
 
You didn't mention flow rate.

The rotary vane (Gast) pump is the usual supply for air at 10 to maybe 45 psi. They are from fractional to 1 1/2 HP, some are oil less.

They supply the suction and the blast on most printing press feeders and paper folders.

The regen's tend to be of higher power and lesser pressure. They are flow machines, they don't do well below a certain flow rate.

The really small ones aren't worth diddly-dingus, I have one, I know. The larger ones are great but they are expensive.

If someone is scrapping a small press like a 1250 Multilith, snatch the air pump off from it. It's about 1/3 or 1/2 hp, single phase and ready to go.
 
Spencer is another make. I have one that puts out 46 cfm to 31 inches of H2O, motor draws 2.4A full load. It is currently surplus to my needs. If it would work for you, send me a PM.
 
The air source for most HVLP spray systems is a two or three stage vacuum cleaner motor. I don't know what the PSI and CFM range is on these units, but it's likely in the ball park of what you are looking for. The beauty of these, is they are readily available in most towns.
 
What you are looking for is a regerative blower, a turbine.
This is not true, they will not deliver the 10-20 psi that the OP stated he needs. Also understand that these blowers have a minimum flow rate or they will overheat and burn up, learned that by experience. So if you go this route do your home work. The compressor is usually sized for the job at hand and may use a bypass valve for keeping the flow up and regulating the air delivered to the job.
 
Jim K.: The motor on my Spencer is unmarked, but I recall it is 1/3HP. Maybe a 1/4? Motor draws 2.4A full load.

Larry G.: I'd have to disagree with you based on my own experience. I replaced a double diaphram Gast pump which put out over 20psi, CFM unknown, with this blower. In both cases I was bleeding off excess air. Plenty of output and preasure.

[ 02-03-2006, 11:41 AM: Message edited by: reggie_obe ]
 
depending on the cfm req'd, you may be able to get a used drywall texture blower... or an older "fresh air" pump. They are both essentialy the same idea, as has been mentioned here, rotary vane units, will run for hours, and put out between 10 and 35 or so psi.

Billy Boy: what cfm do you require? or, if unknown, what pressure and orfice size are you currently setup with, and with appx how many feet of line?

Might try diggin around Ebay under Bullard, Graco, Gast, MSA, Breathing air... etc. New they are overpriced (like everything eh?
) but I have seen several go very cheap. Another option is an older style drywal blower that has a 1/2hp or so motor with a recip piston head at each end, they were a bit noisier, and have the disadvantage of being recip, as opposed to the rotary vane pums....

Tim
 
unless the compressor is running all the time, you dont neccessarily know the cfm required.

if your comp starts and stops normaly, you are obviously using less than the cfm it can produce.

however, if you know the cfm ...just because you do... great, or you can calculate it by orfice size, and pressure.

You were looking for pressures of 10 - 20 psi, I dont think ( but admittedly I dont know) that smog pumps produce that much pressure....

JR:... have you used a smog pump, or verified the pressure output?

Tim
 








 
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