What compressor for 10 CFM @ 15 psi continuous that is relatively quiet?

A peculiar application needs 10 CFM or so at 15 psi, needs to run 24 hours for a couple of months and needs to be fairly quiet. Also, don't have thousands of dollars in the budget for this so a nice Kaeser screw is out. It seems like a real high speed centrifugal would work, but I don't know a source or if they are even made for this purpose. Gast makes some vane pumps that can produce the air, but specs say 80 dB - can that be quieted down with an intake muffler? Is there some other technology? Scroll maybe? but they all seem to be 100 psi plus and hard to find an inexpensive one....

Any ideas?

A high speed centrifugal blower is far from cheap, and it is also far from quiet. Dollar for dollar, the Gast unit will probably do just fine.

The Gast compressor is a vane type unit. It can be used as a motor as well as a compressor. The noise from the Gast is virtually entirely due to the air flow. A muffler can be added to it very easily that will make a big difference. This is probably a good time to call the Gast folks and talk to their technical department for their thoughts. You can certainly buy a Gast with noise mufflers for a whole lot less than anything wlse.

Take a look (listen) to these, I'm impressed.
http://californiaairtools.com/
JR

Almost any comp. can be throttled down to lower pressure. Find the quiet one and set the high/low switch back. Use a large enough storage tank and the comp. will run seldom to maintain that pressure and volume. Please do not confuse pressure with volume. A comp. can put up 200psi but if there is no volume it must run constant to keep up.

The Gast seems to have to be fairly large and constant running (like 1.5 KW for this much air). Also their operating instructions have a shutdown procedure that probably isn't going to work in this situation, not sure what the consequences are of not following but I gather rusted up. I suppose I should call Gast. That California Air one does seem pretty quiet, might get me what I need. I can't remote the noise source in this case - it is already half way between the complaints!

swarf_rat said:

I can't remote the noise source in this case

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Can you move the compressor vertically? How about the compressor at a distance and a 10 gal reciever close by?
JR

A thought.

24 hrs for 2 months = 24 x 60 = 1440 hrs

Is relaibility and continuity od air supply critical?

If so, expecting something ''cheap and cheerfull'' to run 1500 hrs continuously could be asking for trouble.

Or to put it another way Say a car averages 40MPH ... X 1500 hours = 60,000 miles or 1000 miles per 24 hrs??

It could be an application for a belt driven Roots blower with an automobile muffler on the inlet.

I don't know about dealing with noise, but a roots blower is an ideal match to your pressure and cfm requirements.

10 CFM is roughly 2 HP worth of air, get a little 5HP portable on a 20 gal tank, crank the reg down to your 15 PSI, duty cycle should be in the 55% range according to my calculations.

You can pick up a 5 horse (oiled) pump in the 400-600 neighborhood.

Rip one off the hood of the neighbourhood quarter miler?

Well I ordered up one of the California Air units after talking to them, we'll see. This is running in a tin walled shop in Virginia, there are neighbors who don't want to listen to it all night (or all day either). No where to move it up, down, or sideways. I don't care myself, I'm going back to California and I damn sure won't hear it from there! But they will shut it down when I leave....

I started with a Home Depot "1.5 hp", "4.0 CFM" model. It is extraordinary that they can sell this for $99. I couldn't even assemble the parts for $99 if they were free. Someone has to make them, assemble it, box it, ship it to the USA, pay duty, give HD 20% or more. On the other hand, it doesn't actually have to work, and it doesn't. I am about to take the second one back. It is about 95 dB, the first one leaked oil right through the porous crankcase casting, the second one is blowing oil out the breather and out the airlines too. I am running it at about 35% duty cycle (50 seconds on, 100 off), I think they are made for about 2% duty cycle. No way its producing 4 CFM. Still, its only $99...

I was thinking Roots blower or geared supercharger, but I suppose that is as expensive as some other technology. A little tiny turbocharger will do this easily. Can't use a 5 hp compressor, not enough power in the building, no 3 phase either which leaves out an old beater screw or scroll. I really like the idea of the goatskin leather bellows, with some sweaty old guys in dirty overalls pumping away - but I guess as long as we are imagining things we might as well make it sweaty animal skin clad young women, and not much animal skin either.

Talking to the California Air guy, he was up on the duty cycle thing, and realized that while one minute on and 2 off is 33%, so is 2 months on followed by 4 off. They actually (according to him) have their compressors tested by an independent house, he said this one will run about 90 minutes continuous and then shut down from thermal overload. The 3000 hour life they claim is supposed to be what the test house found. Didn't think there will be a problem if it is cycled 30 or 40% on a reasonable period. 3000 hours will be plenty I think. That's nearly a year at 33%, 24/7.

Shadon said:

10 CFM is roughly 2 HP worth of air, get a little 5HP portable on a 20 gal tank, crank the reg down to your 15 PSI, duty cycle should be in the 55% range according to my calculations.

You can pick up a 5 horse (oiled) pump in the 400-600 neighborhood.

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CFM and horsepower do not equate unless you consider the delivery pressure. At 15psi, I doubt 10 cfm will require 2hp. I guess I should add that in order to use low hp in this case, you have to compress the air up to the required pressure and no higher.

thermite said:

Suspect that is slight 'overkill'. Mebbe three orders of magnitude worth of 'slight'?

Some of the forge and glassworker/ jeweler natural gas and air blowers were pretty quiet, but most were not Rootes type AFAIK, nor do I think they got quite up to 1 ATM of pressure, either.

Bill

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That's where pulley sizes on the blower and motor become a significant part of the calculation. There is actually a logical basis to this thought. Father's company sold a line of grain conveyors in the early '60s that used Roots blowers to provide the air to move the grain. Worked very well with little maintenance.

thermite said:

De-rated A/C compressor might easily pull the volume at that low a pressure. Not sure about the oiling and oil-recovery of it though. The oil-less std compressor in an acoustic box is probably better. A mere 1 ATM and 'silent' almost cries out for goatskin leather bellows, hence the pipe-organ ref.

Bill

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A typical theater pipe organ runs at 15 inches of wind which translates to .54 psi Our little Wicks church organ has blower noise so loud the blower had to be installed in its own garage

You people are crazy...... A supercharger? that aint gonna work so well

How about an old polution pump off an 80s car, Ford in particular. I heard of people using them way back when to pull a little vacuum in the crankcase. I think I've also heard someone said of a "poor man's supercharger" for small motor application.

I have no idea what kind of flow or pressure you might get, but it might work for that low volume and pressure. It sure as shit would be a very cheap option. It should be quiet and run for quite a while. I'd try that out first

Paxton makes industrial centrifugal blowers.
Gardner-Denver makes industrial roots blowers. (Dynaflow)
Grain elevators use both of them. Other industries as well.
They both have pressure curves on their web sites.

--Doozer

I think a supercharger would work rather well, its just too expensive to put together.

Compressing 10 SCFM to 15 psi should take about 0.5 HP in a single stage piston compressor, according to the equations.

Find a friendly Johnson Controls technician, pick his brain.

I could explain myself, but I'm feeling a bit smug in my knowledge base.

swarf_rat said:

I think a supercharger would work rather well, its just too expensive to put together.

Compressing 10 SCFM to 15 psi should take about 0.5 HP in a single stage piston compressor, according to the equations.

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But you are talking bout something that is meant to run well into the 100s of CFM ideally ..... be a lot of waste, besides waste of money. You could figure on running it slower, but then you'll get a lot of "leakage", again making it less efficient. If it were me, I'd go to a salvage yard and get a used pollution pump for a few bucks and try it. Just my thought