Shop Air Compressor using Auto AC Compressor

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Toymaker

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A few months back I purchased an Auto AC compressor (Denso 10S15C) to see if I might be able to use it on my steam turbine project; I ultimately concluded that this compressor was far too large and ended up building a much Smaller Swashplate Compressor.

Not wanting to simply toss the Denso compressor into my junk parts box, I decided to build a shop air compressor using it.

Automotive AC systems mix a bit of oil with the Freon to keep the pistons in the compressor lubricated, so I needed to add an oiling system that continuously puts a small amount of oil into the air intake. My solution was to place a very small tube into the compressor's air intake so that the air sucked into the compressor would also suck a bit of oil at the same time (using: Venturi effect). That little red tube in you see in the last pic below is the spray tube from a can of WD40 :).

The tank is an aluminum air-brake tank used on large trucks. Electric motor is 1/3 hp. Pulleys are 2" and 7". Metal braded tube was cut from a section of hot water line to which I added AN fitting to both ends; I was a little concerned that hot compressed air would soften the rubber inside the braided metal tube, but so far it's holding up. Pressure regulator and gauges are all from eBay.

So if anyone else is crazy enough to build their own air compressor using an old automotive Air Conditioning compressor,...this method works. :).

Shop Air Compressor 3.5 to 1 Pulley.jpg
10S15C from above.jpg

10S15C Venturie.jpg
 

Larry G.

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Excellent job. :)

Refrigeration systems, and vacuum pumps made out of salvaged AC compressors, can recycle the same bit oil rather than use a contiguous supply.
But... AC systems fastidiously remove all moisture from the refrigerant. An _AIR_ compressor will suck in atmospheric moisture and mix it with the oil and make the famous tan cream that settles in the receiver tank. :(
 

Toymaker

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Excellent job. :)

Refrigeration systems, and vacuum pumps made out of salvaged AC compressors, can recycle the same bit oil rather than use a contiguous supply.
But... AC systems fastidiously remove all moisture from the refrigerant. An _AIR_ compressor will suck in atmospheric moisture and mix it with the oil and make the famous tan cream that settles in the receiver tank. :(

Thanks for the compliment :)

I only use my little DIY air compressor maybe once a month to top off car and motorbike tires and to blow the accumulated dirt out of several house fans, so I'm not too concerned with the need to frequently drain the receiver tank. But I am concerned with long term corrosion. The main reason I chose Aluminum for the tank was to help avoid metal corrosion from that famous tan cream, which here in humid Thailand, will most likely contain far more water than oil. All the Googling I did led me to believe that aluminum tanks tend to have longer lives than steel tanks.

What's your experience on steel vs aluminum receiver tanks?
 

Larry G.

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I've never seen a commercial compressor with anything but a steel tank. Even when the weight of an aluminum tank would offer a distinct advantage on a portable unit. "Follow the money" is still true. :)
 
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Personnaly, For any receiver, aluminium, steel, plastic, etc, I would check material thicknesses, permissable stresses and check the Regs in your location - or ASME, or other internationally recognised regulations - and "follow the book for the Design Working Pressure" for the receiver, relief valve size, etc. As those will be the basis for the design for its original use. And test it annually for hydraulic test, and weekly for over pressure relief valve function. Even if it is not certified. If it is good practice in industry, it can't be bad at home.
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RM-MN

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Firefighters use aluminum tanks for their air in firefighting because of the reduced weight. They have to be fiberglass wound to help them hold the pressure and have a much shorter lifespan than steel tanks so they have to be replaced more frequently. There must be some reason air compressors always seem to have steel tanks.
 

Toymaker

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Personnaly, For any receiver, aluminium, steel, plastic, etc, I would check material thicknesses, permissable stresses and check the Regs in your location - or ASME, or other internationally recognised regulations - and "follow the book for the Design Working Pressure" for the receiver, relief valve size, etc. As those will be the basis for the design for its original use. And test it annually for hydraulic test, and weekly for over pressure relief valve function. Even if it is not certified. If it is good practice in industry, it can't be bad at home.
K2

As some of my Australian friends like to say, No Worries Mate. The Aluminum tank I'm using was made for and sold as an air compressor receiver tank to be placed on large trucks for their air brake system. The tank is rated for 220 PSI and I limit the max pressure to 100 PSI,...which is plenty enough for my uses.
 

Toymaker

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Firefighters use aluminum tanks for their air in firefighting because of the reduced weight. They have to be fiberglass wound to help them hold the pressure and have a much shorter lifespan than steel tanks so they have to be replaced more frequently. There must be some reason air compressors always seem to have steel tanks.

There are several companies making shop air compressors with aluminum tanks; here's a list on Amazon

Two main reasons I chose an aluminum tank over steel are because aluminum tanks are said to have a longer life, and they don't rust. I live in the tropics where a dry day is still over 70% humidity, which means, even if I only use my compressor once or twice a month, the tank will almost always contain some amount water, which will lead to rust inside a steel tank but wont do much damage an aluminum tank.
 
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Toymaker, the reason for blowing-down a receiver daily, is to minimise the water left in the receiver that causes corrosion. So it is a very good idea to follow normal practice. Even in Aluminium..
RM-MN - Steel is much cheaper than aluminium, "strength for strength", so Unless "Minimum weight" is a high priority, Steel wins. Aircraft use aluminium receivers I think?
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Bentwings

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i worked in a fab shop that did occasional RV repair . A unit cam in with leaky water tank. It was aluminum and not new by any means one of the guys hooked the shop air 120 psi to the water tank but forgot about it . It was floating on the water tub full of water to check for leaks . Suddenly there was a building shaking explosion . Water flew everywhere the tank didn’t just split it blew it into several parts that went flying around the shop the large water tank 30-40 gallons was nearly flattens an water sprayed all over plus th remaining air hose was wildly flopping around with a jagged piece of aluminum held on by the tire valve and clamp . So much for the water tank a good lesson in why you don’t test pressure vessels with air fill with water and submerge use hydraulic pressure so if it splits it just drops pressure no explosion . GOOD THING IT WAS NOT IN THEVRV aRV fire fighter tanks are often wrapped with carbon fiber and epoxy coated much mor expensive but safer.
Firefighters use aluminum tanks for their air in firefighting because of the reduced weight. They have to be fiberglass wound to help them hold the pressure and have a much shorter lifespan than steel tanks so they have to be replaced more frequently. There must be some reason air compressors always seem to have steel tanks.
 

Toymaker

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Wow Bentwings, that's quite a story,... and avoiding such an explosive occurrence was my primary reason to purchase a NEW receiver tank instead of picking one up at the local auto junk yard for far less money. Still thinking of safety, I chose to use an aluminum tank that was made for use on large truck's air brake systems because I suspect these tanks were made to take a lot more abuse and vibration compared to stationary receiver tanks.
 
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A job I designed back in the early 80s required a large-ish (100L?) receiver for air at 28bar. We made our own in the factory Steel fab shop... until a bright spark doing cost reductions decided that our 200 p.a. was tiny volumes compared to "truck" makers, so we changed to a truck receiver (from a truck receiver supplier) at a small fraction of the cost... We had certified men welding, they had semi-automatic machines... Their receivers and fittings were made in the tens and hundreds of thousands of assemblies, so overheads etc. were tiny compared to ours. And their NWP of 30 bar was Ok for our 28bar application... We gained for cost, quality and certification.
When my brother started diving in the 1960s, the "commonly used" air receiver used by divers was an ex-WD aircraft air receiver, re-furbished and certified.
I have seen a "pressure vessel" from a fire extinguisher used as a domestic air receiver - duly examined and tested by a professional, - as well as a Propane Gas cylinder!
But I would NOT use a "home welded" job, unless by a known certified welder, to a known certified design and using all the processes and materials specified by the factory.
So there are "sensible alternatives" available at relatively low cost, providing they are properly cleaned, examined and tested...
And my Dad's mate had a large truck wheel and tyre outside his garage, leaning against the back wall, with an air-line connected so it was used as the receiver! He set the relief valve below the Max pressure on the tyre wall. Good enough for his spray booth.
K2
 
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Toymaker

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A job I designed back in the early 80s required a large-ish (100L?) receiver for air at 28bar. We made our own in the factory Steel fab shop... until a bright spark doing cost reductions decided that our 200 p.a. was tiny volumes compared to "truck" makers, so we changed to a truck receiver (from a truck receiver supplier) at a small fraction of the cost... We had certified men welding, they had semi-automatic machines... Their receivers and fittings were made in the tens and hundreds of thousands of assemblies, so overheads etc. were tiny compared to ours. And their NWP of 30 bar was Ok for our 28bar application... We gained for cost, quality and certification.
When my brother started diving in the 1960s, the "commonly used" air receiver used by divers was an ex-WD aircraft air receiver, re-furbished and certified.
I have seen a "pressure vessel" from a fire extinguisher used as a domestic air receiver - duly examined and tested by a professional, - as well as a Propane Gas cylinder!
But I would NOT use a "home welded" job, unless by a known certified welder, to a known certified design and using all the processes and materials specified by the factory.
So there are "sensible alternatives" available at relatively low cost, providing they are properly cleaned, examined and tested...
And my Dad's mate had a large truck wheel and tyre outside his garage, leaning against the back wall, with an air-line connected so it was used as the receiver! He set the relief valve below the Max pressure on the tyre wall. Good enough for his spray booth.
K2

Wow!! 100 Liter receiver is a really big tank for a truck,... I've certainly never seen one that large,...must be some really big trucks.

In my younger days, I've used discarded Freon tanks as portable compressed air tanks,...their working pressure is typically 350psi to 400psi so the 120psi from my home shop air compressor was well within safety limits. Another benefit is they're made with pressure fittings that are easy to find and purchase. But the wall thickness on Freon tanks appears terribly thin, so I always handled them with a bit more caution when they were fully charged.
 
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Maybe I am wrong with my memory of sizes.... or maybe they were for something else...? But I'm sure the factory making those receivers mass produced receivers for trucks.... which is why they were so much cheaper than our custom made receivers. I wonder if they were for road-transportable compressors - for road jack-hammers, or whatever?

About 4 ft long and a foot diameter or maybe a bit bigger? Maybe that's not 100L. Vague memory, amongst all the other clutter! I remember the steel frame for the equipment that used the air in the air motor. About 2m / 6ft, high, and 2 ft square at the top. Receiver was hung on 2 brackets on one side, mounted vertically, inside the frame. I had to change the mounts for the new receivers on my drawings.
K2
 

Bentwings

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that should be ok. I suggest attempting to look inside for excess water corrosion as well as exterior. My late son drove over the road for some time air line often froze up in cold weather unless tanks were purged often. It was one part of truck driving he didn’t like . Messy cold and wet . Not a nice way to start the day or night drive .

Maybe I am wrong with my memory of sizes.... or maybe they were for something else...? But I'm sure the factory making those receivers mass produced receivers for trucks.... which is why they were so much cheaper than our custom made receivers. I wonder if they were for road-transportable compressors - for road jack-hammers, or whatever?

About 4 ft long and a foot diameter or maybe a bit bigger? Maybe that's not 100L. Vague memory, amongst all the other clutter! I remember the steel frame for the equipment that used the air in the air motor. About 2m / 6ft, high, and 2 ft square at the top. Receiver was hung on 2 brackets on one side, mounted vertically, inside the frame. I had to change the mounts for the new receivers on my drawings.
K2
 

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