Air compressor quandary

--I've got a need for a fair supply of 80psi air for a trade show display. I'm using one of those little Kragen jobs that has maybe a 2 cuft tank on it. Trouble is, it's on nearly all the time to supply what I need for my widget. I'm trying to find something of equivalent size (i.e. small enough that one old fart can hump it in and out of a small pickup and drag it to/from booth) but that runs silently. Maybe a small screw compressor? Looking for options. Suggestions?

Reply to
steamer
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Small, high volume, quiet - pick two.

The normal solution for this kind of thing is a remote compressor and a long air hose.

Reply to
Pete C.

Which begs the question -- what CFM do you need, really? If what you have is running flat out then your answer may be on the nameplate.

Assuming you have to stay in the confines of your booth, what about the compressor and a cabinet to muffle noise (with good air circulation to carry away heat, of course).

Reply to
Tim Wescott

On 28 Apr 2009 17:10:59 GMT, the infamous steamer scrawled the following:

Consider a compressed nitrogen tank, Ed. Some contractors work for weeks on one filling. Whatcha running? I wonder if they make adapters for scuba tank regulation...

An added advantage is that you can change the air in your truck tires. I hear that it's lighter (for better fuel economy) and it never leaks out of the tire. You'll Save The Planet!

------------------------------------------------------ No matter how hard you try, you cannot baptize a cat. ----------------------------

Reply to
Larry Jaques

It's really not significantly lighter, but they use it in racing car tyres because it doesn't oxidise the rubber when it gets hot. I don't think the leak rate is much different but, with air, the pressure will drop as you oxidise the rubber because you use up the oxygen.

Reply to
newshound

A standard SCUBA 1st stage regulator outputs about 140 psi. Some are adjustable potentially down to 80 psi, or just feed a regular air regulator from that. A dive shop can probably sell you an old 1st stage for non-dive use cheap. Standard AL80 SCUBA cylinders are nominal 80cf capacity at 3,000 psi, and they aren't very expensive to rent. Just remember to use a lubricator downstream in the air lines if needed since the SCUBA air is very clean and dry.

Reply to
Pete C.

Reply to
stans4

On Tue, 28 Apr 2009 20:16:44 +0100, the infamous "newshound" scrawled the following:

According to some website stats, I think it was touted as having larger molecules so it leaked less easily.

Ah, I found the "extremely important paper" which contains that info:

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------------------------------------------------------ No matter how hard you try, you cannot baptize a cat. ----------------------------

Reply to
Larry Jaques

Most gas suppliers will supply compressed breathing air in the large cylinders, and cheaper than other gases. But I think he needs more air than that, if his current compressor "as he stated" is running most of the time.

Reply to
Tim

I'm guessing the compressor is around 2 cfm at 80 psi. Not insignificant. Others mentioned using various compressed gas tanks, these are in the 100 to 250 cubic foot range. That calcs out to 1 to 2 hours per tank, pretty spendy.

I think you would be well served with a small piston style compressor with a 1 hp motor, 10 to 15 gallon tank.

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speedair compressors can be outfitted with different sized motor pulleys, if you go to a smaller motor pulley, the compressor speed drops, the power needed drops, and (most importantly!) the noise drops.

I had a client that got suckered > --I've got a need for a fair supply of 80psi air for a trade show

Reply to
RoyJ

I'm in the mid-east, nitrogen doesn't expand as much as air when hot. When taking a road trip, air is replaced with nitrogen. And it's hot over here, normal summer hi 120-124F

Reply to
Rick Samuel

On Wed, 29 Apr 2009 06:52:21 +0300, the infamous "Rick Samuel" scrawled the following:

Hmm, at those temps, all tires turn into flotation tires, so why worry? ;)

------------------------------------------------------ No matter how hard you try, you cannot baptize a cat. ----------------------------

Reply to
Larry Jaques

--Not up to the challenge: a two day show that runs for 8 hrs per day. Gotta go air compressor. Am lobbying show management to provide a monster air compressor so that various exhibits can sip from it; wait and see..

Reply to
steamer

--Trouble is if I don't use air I'll have to retune all of my whistles...

Reply to
steamer

--Thanks; that's useful!

Reply to
steamer

More marketing hype. Both air and nitrogen will follow the ideal gas law (PV=nRT) very closely at the temp and pressure we're talking about. I suppose *dry* nitrogen may be somewhat better behaved than

*wet* air, but I'll let someone else speculate on whether that makes any practical difference.
Reply to
Ned Simmons

No one has mentioned a sealed refrigerator compressor. Whether you can find one large enough depends of course on your exact requirements. Dental compressors like this are also pretty quiet...

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Reply to
Ned Simmons

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  • a generous supply of strong, good looking young women to operate them. Attracts traffic to booth. ;-)
Reply to
Ecnerwal

It may be all to obvious, but is there any way to reduce the amount of air needed? We had a situation like yours once only we needed about 10 cfm at 60 psi. The compressor that came with the machine WAS one of the oiless kind, 4 cylinders, 220V 3 phase, 3600 rpm; NOISY. We found that we could power one wasteful valve with the excess capability of one vacuum pump and another part would run for a day at a time on a one pound can of F12. (don't flame me for this, it was in 1967).

One other alternative might be to rent a bunch of scuba tanks. The air is at about 2500 psi and must be cheaper than nitrogen.

Actually the bigger the compressor and tank the less often it has to run.

We have built lightweight insulated boxes around compressors to cut the noise down.

Maybe even an old air conditioner's compressor (the bigger the better). They can supply pretty high pressure and are often relatively quiet. Just be sure to add a little compressor oil from time to time.

Lastly, is there any way to "dummy" your demo (by adding an electric motor or whatever) for casual passers-by? Then, when you have a "live one", you can switch the the real thing.

Pete Stanaitis

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steamer wrote:

Reply to
spaco

Screw compressors are Big, Heavy, Not meant to be portable, and Expensive - $4K for openers. Meant for an industrial setting where you set it up in the back room and let it run, or for an engine drive compressor in a trailer for running jackhammers.

My suggestion for 'portable fits in back of truck' - get one of the belt-drive wheelbarrow style Oil Lubricated compressors, they aren't that hard to get in and out of a truck. A steel ramp makes it easy to roll in and out.

Look at the DeWalt Emglo D55580 for an example - 2 HP 8 gallon, 8.4 CFM @ 100 PSI, convertible between 120V and 240V, convertible between unloader constant run and pressure switch start-stop.

(More than six to eight starts an hour can burn up the motor from Short Cycling, so you switch to constant run. Makes the convention center folks happier too, no start surges dimming the lights and causing mayhem with electronic gear.)

The belt drive means the compressor head turns slower(1070 RPM) and is therefore a whole lot quieter than a 3600 RPM direct-drive unit. And oil lubricated means 'lives a lot longer'.

Then build a seperate modular sound cover box for over it, sized to fit under a standard table - sandwiched plywood and rigid foamboard insulation, with removable hinges to hold the edges together, and clevis pins or diaper cotters to hold it together. Make two sound labyrinth boxes as the end panels, one for 'Cool air in' with two of the big 6" Muffin fans for cooling air, one for 'Warm Air Out'.

(Taken apart, it should fit in the back of a truck with the compressor.)

Now if you have an open trailer hitch on the truck, you can buy a little 3X4 trailer chassis and build your little "Dream Compressor" on that in a permanent sound cabinet. Put a good nosewheel on the front, two people roll it right into the convention hall, and you toss a tablecloth over it and make it part of the display.

Or build the trailer long and skinny (4X6) and short so it can double as your demonstration work table - put landing jacks at the rear corners, make the tubing tongue removable so you aren't barking shins on it all day, and start your pitch. With the soundproofed compressor and other support gear you need built right inside.

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Reply to
Bruce L. Bergman

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