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Quiet air compressors
We have at least one new build project in a school classroom that does NOT have compressed air plumbed in. There is really no place to locate a compressor outside the room, so having a quiet compressor takes top priority, even if it is at the expense of some durability. The quietest one I can find advertised is the California Air Tools CAT 6310, at 60 Db. That is not much louder than a refrigerator. It is rated at 3.8 cfm, which will run about anything a group of kids will need to build and RV-12.
Have any of you actually bought and used this thing? I would like a report on one before I spring for it. They are less than $200 at HD and Lowe's. Thanks Bob |
I have a 3hp, 220v ingersol rand compressor. It has a 60 gallon tank and is very quiet, plus it doesn't need to run much with that big a tank. Northern Tool Supply, $800
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Whatever you end up with, if it has a threaded intake port, you can find an intake muffler for air compressors at Grainger.
Belt driven and oiled compressors are quieter. |
That's really impressive if they can get that quiet. I looked at CAT's web site and the 6310 is listed as "discontinued" but they have a replacement model.
I guessed it might be a rotary screw design but it turns out to be a double piston type. Really impressive if they can get a reciprocating unit that quiet. |
You need at least 5.5 CFM. Anything less is only good to fill bicycle tires.
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or...
a bigger tank (or multiple tanks).
Many years ago, my dad told me about a work area in an electrical supply house that had a large air tank being fed by...wait for it...a re-purposed refrigerator compressor (as in, out of the back of a refrigerator). It quietly hummed in the background, & due to their minimal needs, they never ran out of air. No clue how they avoided lube issues; perhaps it never spat out its oil while running. Charlie |
I bought a California Air Tools CAT-4610A for my hangar. It's amazingly quiet. I also grabbed an auxiliary 10 gallon tank to plumb in for extra capacity.
Unless you're sanding/buffing or using something that's continuously running, I think it'll be fine. |
An option which is both quiet and affordable is an old 2-stage compressor.
The one in this photo is from a small automotive garage which went out of business a few years ago when the mechanic retired. I believe it cost $200-$250. It is large and quiet. The flywheel acts as both the drive system - to two pistons - and the cooling fan which blows on a coil tube connecting the output of the first piston to the input of the second. (The pistons are located front-to-back.) I have the pressure switch set to run at 150 PSI and cut out at 180 PSI at the tank. A regulator is set to 100 PSI to the various tool drops. Depending on the locations, there can be additional water separators / filters, inline oilers, etc. The original belt drive is quiet and dramatically reduces the RPMs of the pistons. If this were still not quiet enough, it could easily be "boxed in" with HVAC insulation. FYI: I listened to the video and - having compressors like the first two - I would estimate my two stage is as quiet or quieter then the California Air. Additionally, the old 2-stage compressors have a much gentler sound - more of a chuggah-chuggah-chuggah sound. |
Wow, thanks for the replies! A couple notes: absolutely can't box one in--fire codes. The "repurposed refrigerator compressor" really made me smile. Had one of those in an art studio back in the 80s. It was out of a '47 Ben Hur deep freeze, and ran at most four airbrushes. Really couldn't hear it, unless you paid attention. Used it for years with no maintenance.
Think I will have to give the CAT a try, and will plumb in a larger tank if I have to. Normally only using air drills and rivet pullers, fairly low volume devises. This is the first time we have had a dedicated classroom (not used for any other classes) but size and appearance will make a difference. We may be able to get one free, or at least at a good discount. We won't be starting until August (school year) but will fill you in on how it works out. It certainly sounds like a simple solution to the noise problem, and is portable. (I do have a two stage at home, but it is staying!) Bob |
What I found with mine
(Quincy two-stage) is that the highest noise level is not at the intake silencer but at the vent slots in the motor housing where its internal cooling fan puts out a fairly loud hiss. This was as measured by an iPhone noise-metering app at as close to uniform distances as I could eyeball. The motor cooling fan is 3 or 4 dB louder than anywhere else around the compressor.
Just a random data point :rolleyes: -Stormy |
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