Air compressors are often loud, raucous machines – but they don’t have to be. [Eric Strebel] built a remarkably quiet compressor using parts salvaged from an old fridge. After several years of use, it was due for an upgrade (Youtube link, embedded below}.
While performance of the original setup was good, [Eric] desired a compressor with more capacity for his resin casting activities. A 15 gallon air tank was sourced from a damaged Craftsman brand compressor, and pressed into service. The build involved plenty of sheet metal work to mount the various components, as well as an upgrade to the pressure regulator.
During the refit, [Eric] takes the time to answer questions from the audience about his original build. He notes that the fridge compressor has worked well without using any noticeable amount of oil, and that there was a problem with water build up in the original tank which has been solved in the new rig.
It’s a great example of building your own tools, which can provide years of service if done right. Check out our write up on [Eric]’s first build, or his work on photogrammetry. Video after the break.
My church has an air compressor to supply air to the hot water heating valves.
I think it has about a 20 gallon (75L?) tank.
Last month I decided to see if anyone periodically drains the moisture from the tank.
About 5 gallons of water later…
I wonder does high pressure air dissolved in high pressure water cause the inner surface of the tank to rust at an accelerated rate once the protective coat of pain on the inside starts to fail.
I would expect it to, though the few old tanks I’ve seen always seem better on the inside than out. Probably as the coatings are kept in the dark with no real abrasive action either.
With all that water in the system galvanic action is the bigger threat for rust.. But with similar metals should be fine there.
Typical. Even setups with automatic drains may have this issue if the drain is set up wrong or sized wrong.
The condensate will rot out the tank from the inside, typically just outside the weld (in the heat affected zone) for the drain or at a bottom side weld seam. Letting the water sit makes it worse, due to electrolysis, oxidation, and all kids of stuff that will grow in it, some of which may damage the metal.
Have you seen a tank failure due to corrosion? The fear would be a catastrophic explosion, but I suspect that in practice they just get to the point where a pinhole appears and lets all the air out.
That’s usually what happens with rusted out steelies on cars.
Force always picks the path of least resistance, and a pinhole is more convenient than violent rupturing a steel vessel.
yes, but usually with another trigger than the corrosion, such as external impact. THe best are when the tank goes near solid with water due to not draining, and starts blowing water out the safetylike a shower every time the air pump cycles.
One of the main causes of catastrophic failure goes with the same lack-of-maintainance issue: oil vapour. Combustion evens are not that unusual, and a corroded tank may have significantly worse outcomes, and is a sign of greater risk due to poor maintainance.
If I see significant oil in the condensate, that is a primary cue that other issues are likely.
(pressure vessels are not presently a primary part of my job, but are still in play)
Seen a couple fail from internal corrosion. Each of them developed leaks around the drain cocks. Not a bad enough leak to hear but a slow leak that takes 30 minutes to drain a 20 gal tank filled with 80PSI. When it gets really bad just trying to loosen the drain cock from the tank is enough to break the weld around the slug it’s threaded into.
Where I live every compressor is supposed to be drained regularly, and pass a pressure test ever 2 years. The test pressures the vessel with water and is pressured over the max rating by some percentage. In practice most home compressors just sit there, rusting, waiting to blow up and kill someone.
I did the same at my high school. They had a air compressor supplying the shops up in an alcove. I asked the teacher if anyone ever drained it and he didn’t know. So we grabbed a ladder and opened up the door. There was a pipe coming off to a valve that sat horizontally and opened that. It proceeded to shoot water a good 30 feet out into the parking lot behind the school. There must have been 30 or 40 gallons in there.
I use a fridge compressor for compression and vacuum. Awesome for indoor use / places that are sensitive to noise.
For quiet compressors, check out the Fortress brand compressors at Harbor Freight (I know…) They are very quiet. Neither of the models has the output flow (CFM) I need, but when larger models come out I plan to buy one. The existing models can probably put out more air than a refrigerator compressor though.
My uncle did one of these 60 years ago on the farm, low CFM but quiet – worked for many many years
Fridge compressors are a huge untapped resource. While at school I found a rusty old fridge compressor. Convinced it was on its last legs I considered opening it up, but ended up using it as a solder sucker. No filter! No doubt some solder blobs made it through the entire system. I used it for years until my mother, convinced it was as it looked, junk, threw it out.
“”fridge compressor has worked well without using any noticeable amount of oil””
I’ve used up several compressors now because every single one of them pisses the oil eventually until there isn’t enough left in for cooling/lube.
It gets flung around so much that it ends up getting taken into the air pickup, like it’s designed to really.
So typically have to mod the air pickup.
Would love to find one that “just worked”
But they are a great cheap way of getting silent air.
did you know fridge compressors are supposed to pump the oil around as well?
Yes
They all are
But it seems some “on the internet” just dont do this
??
“… He notes that the fridge compressor has worked well without using any noticeable amount of oil…”
What? How does he know / determine how much oil is used? [I have not viewed any of the attached material].
I work on air conditioner systems, including replacing the compressors, evaporator coils, condensing units. Yes, I use silver solder (or “sil-foss”) to attach the component parts.
Refrigerators and freezers are miniature air conditioners (albeit very small, compact, powerful A/C units). When an A/C system is set up, A/C lubricating oil is injected into the system along with the refrigerant (“Freon”).
EVERY A/C system and refrigeration unit relies for its long-term operation (and a well-set-up A/C system–read this as “no leaks at all”–will run for years and years, until the bearings in the compressor fail) on the lubricating oil carried around the entire system along with the refrigerant. This is how the compressor gets lubricated, much as a 2-cycle internal combustion engine’s only method of lubrication is by the oil contained in the fuel used for combustion (I just gave my power company–for money–a 30-year-old refrigerator which was still going strong).
There is no way for the compressor in an “open” system such as this to be “normally” lubricated. Yes, I know that there have been articles very similar to this since the days of “Mechanics Illustrated”, “Popular Mechanics”, and before; just don’t build one and expect it to continue operating for an extended period of time unless you design in a method of (reliable) external lubrication.
I wonder if the addition of an oil separator and return line would help keep the oil in the system and out of the air flow. Of course some small amount will make it past the filter but those things are pretty damn effective for how simple they are.
I have an old (50 years??) commercial refrigeration compressor, 1/2 HP. Been running it for many years now. I use a freon tank.
Geez, look at the old York A/C compressors found on Volvo 1- and 2-series. Those were a mainstay of the offroad 4×4 community for rock-crawling and mudding. Grab some angle iron, weld in some brackets, and have a nice high-flow air supply on the cheap. Oh, and even better? Add oil periodically as air tools NEED oil to survive. Scroll compressors don’t require the sheer volume of oil flow compared to the old the old compressors, so periodically adding a tiny amount of oil would be the only requirement. My background? A-ganger/submariner, HVAC tech, avid offroader, die-hard old Swedish car enthusiast with a passion for fabricating and saving some money.