DIY high pressure air compressor (3000PSI and more)

[HDB]

Hi all,

I was wondering how high pressure compressors (like for filling a paintball tank or dive tank) work.

A normal air compressor uses an air pump, motor and tank.

Let's say for a regular compressor I have a 4HP engine. The smaller the piston of the air pump, the more pressure it can yield (but the time to fill the tank would increase).

If the above is true (is it?), then in theory it's just a matter of calculating the piston size to yield e.g. 3000PSI.

But I wonder if that is how the 'real' high pressure compressors work.

One day I'd like to make my own dive tank compressor (I know that the air would need to be filtered also). Let's say There's a lot of info on the internet about regular LP compressors but I don't find any real info on HP compressors.

If you could name the required parts, that'd be handy. That way I could Google them.

Any ideas?

[OlderNewbie]

Normally, HP (breathing air, paintball) compressors are 3- or 4-stage compressors with high-pressure (500 PSI and up) oiling systems for the final stage, using special (usually synthetic these days) oils with very high flashpoints. They are dynamically balanced with the stage pressures taken into account. A LOT of engineering is involved.

If you will use this air for scuba, I recommend in the strongest possible terms that you buy a real breathing air compressor. You can contaminate breathing air with compounds, deadly underwater at higher partial pressures, that will not be filtered in the filter stacks and not know it if you miss a small detail somewhere.

More than you probably wanted to know here (unless you will buy one): http://scuba.club.anu.edu.au/gear/compr ... rticle.pdf

Mine's a 4-stage Bauer K14 with three stage filtration and O2 clean air. I bought things a piece at a time and it was still expensive, but as I mix my own gases it's paid me back now.

John

[HDB]

Normally, HP (breathing air, paintball) compressors are 3- or 4-stage compressors with high-pressure (500 PSI and up) oiling systems for the final stage, using special (usually synthetic these days) oils with very high flashpoints. They are dynamically balanced with the stage pressures taken into account. A LOT of engineering is involved.

If you will use this air for scuba, I recommend in the strongest possible terms that you buy a real breathing air compressor. You can contaminate breathing air with compounds, deadly underwater at higher partial pressures, that will not be filtered in the filter stacks and not know it if you miss a small detail somewhere.

More than you probably wanted to know here (unless you will buy one): http://scuba.club.anu.edu.au/gear/compr ... rticle.pdf

Mine's a 4-stage Bauer K14 with three stage filtration and O2 clean air. I bought things a piece at a time and it was still expensive, but as I mix my own gases it's paid me back now.

John

Hi John,

Thanks for replying and the PDF. I'm aware of the potential dangers of making one myself. And I know that making stuff yourself comes with danger etc. The same can be said about making a propane forge, melting aluminium, annodizing, etc. But that are the things that I love to do.

I bought a lathe and some other tools so I can make stuff with them. I like to make stuff and understand the inner workings.

Purely mechanically speaking, ignoring the health aspect, where would you guys start? So still aiming at 200bar (3000PSI).

[Carm]

This is a subject that arouses curiousity...how is high pressure air (~3000PSI) developed for blowing ballast tanks in submarines? Rapid generation would seem a requirement.
No, not going to build one...compressor or sub.

[mcostello]

Making a mistake that shows up 50' under water while You are alone is not the same as making a nice perfectly fitting female tubing cap for the wrong end of the hose! Guess what I did tonight, You don't need 2 guesses.

[hammermill]

A visit to a local fire station may get you a look at a scba compressor.

[CraigS]

Hi,
I have an old Corneilus 3000PSi portable compressor that I would guess was built in the early 50's or just after WWII. It only puts out 1.5cuft per minute but runs like the day it was built. Can't seem to find a photo but on top is a 3400 RPM single phase motor with the shaft running vertical down to the pump section directly driving the crank actually an eccentric if I remember correctly. Three cylinders and pistons protrude from the pump body 90 degrees apart. The low pressure piston is driven by the master rod and the second and third stage driven off the master rod. Exhaust valving is done in the cylinder head but the intake is done on the side of the cylinder with a poppet valve in the center of each piston. Looks more like a radial aircraft engine than a compressor. I bought it many years ago at a city surplus auction, the fire department was using it to fill air packs but it was too small. There were only two bidders and the other guy dropped out after I told him it wasn't a paint compressor, think I got it for about 20 bucks. If it wasn't for the other guy I would have had it for the $1 opening bid.

It is possible to build your own HP compressor for paint ball etc. This guy has a $649 unit that I would think any machinist could duplicate but for that price I don't know who would want to.

http://www.shoeboxcompressor.com/products.html
Craig

[ken572]

Good Morning CraigS

Is this like yours

Picture -1.jpg (36.04 KiB) Viewed 24483 times

Ken.

[OlderNewbie]

Hi John,

Thanks for replying and the PDF. I'm aware of the potential dangers of making one myself. And I know that making stuff yourself comes with danger etc. The same can be said about making a propane forge, melting aluminium, annodizing, etc. But that are the things that I love to do.

I bought a lathe and some other tools so I can make stuff with them. I like to make stuff and understand the inner workings.

Purely mechanically speaking, ignoring the health aspect, where would you guys start? So still aiming at 200bar (3000PSI).

I like to make things, too, but this would be a very complex project with lots of potential for killing whoever uses the air at depth. Bad gas is a killer underwater. I'd have no such objections if what you wanted was a paintball compressor! At least if a cylinder or final stage separator fails you'll probably only get hurt--or even skate if you're lucky.

Anyway, you can find the Bauer parts catalogs online for a start so you can see what you're thinking about getting into. Lots of parts, lots of (unspecified) materials. If you really want to build something get certification papers for everything in (at least) the HP stage.

John

[hammermill]

in the past a web site existed covering a version of the small compressor mentioned. they were interesting. some web searching should turn of the articles. remember it started with 80 psi air