Scuba Tank for silent DIY shop compressor

[Frito]

Hello Everyone, new here and as the title says, I'm interested in DIYing a shop compressor system using a scuba tank and a refrigerator compressor.

There are a few reasons why Id like to do this:

1) I have access to both a compressor and tank for free.

2) A fridge compressor can pressurize several hundred psi, and the scuba tank can hold it without worry of over pressurization.

3) I like DIYing even if it costs a bit more than an off the shelf product.

4) Extremely quiet, can be used within an apartment.


Cons:
1) There is only one inlet on the tank, so everything would have to go in and out via a T from the neck.

2) May need to mount the tank upside down to drain water out, or have a tube that goes into the bottom.

3) If I don't have a way to drain the tank I'll have to implement a drying system using desicant to minimize condensed water in the tank.

Would appreciate any feedback. Ive done some searching on this forum and ive seen alot of threads on using the tanks as an air supply for tools, but i haven't seen anything about using one permanently hooked up to a compressor.

 

[tbone1004]

problems

Even if at several hundred PSI, you'll still need a regulator and some sort of pressure shutoff switch. You may as well use standard shop compressor parts, including the shutoff switch that is more than capable of running the fridge compressor at standard shop compressor pressures

You'll annihilate the scuba tank with moisture and everything else going into it. Normal scuba tank valves have dip tubes to prevent water from entering the valve when inverted so you'll have to remove the dip tube, mount it upside down, then not only have a T, but also a way to blow that off. It has to be aluminum tank if you're going to do it because a steel tank will rust in a heartbeat

Fridge compressors are only about 1cfm, so you can't have a lot of demand on it.

There are tons of videos on youtube of converting fridge compressors to run as shop compressors using standard air compressor parts, I would start there.

My recommendation is to go find the cheapest shop compressor you can get, and just plumb the fridge compressor into it. It's not worth using the scuba tank

 

[Frito]

I was thinking of using a nitrogen regulator and a pressure shutoff relay to control the compressor and air tank output.

Looks like I could probably remove the dip tube. The nitrogen reg has a pressure release valve I believe, so everything could be relieved I think. Unless the pressure relief from the regulator is only internal to the regulator.

 

[tbone1004]

it can definitely be done, it's just whether it's worth doing the way you are talking about doing it, and I would say that finding a "dead" shop compressor on facebook marketplace or craigslist and just swapping the pump out is going to be the most economical way of doing it, but also the most practical. This is getting to be a bit Rube Goldberg, and that's coming from an engineer.....

 

[Frito]

I totally see your point and it is introducing a host of problems just for the option of more than 200-300 psi and the piece of mind that the compressor can never overpressurize the vessel even if the relief valves fail.

 

[diversteve]

two things(and I'm not a compressor expert)

Most scuba fills are between 2400-3000 psi so I assume what yoou're making is to be used to run airtools instead?

Is the compressor Oil-less. Oil under compression can coat your lungs and cause a pneumonia like condition/

 

[Frito]

Yes its specifically for air tools.

Fridge compressors are lubricated with oil. In fact I'd probably remove the oil it comes with and replace it with a conventional motor oil.

 

[diversteve]

replace it with a conventional motor oil.

you might want to check the flashpoint before you do.

My bil has a big compressor he uses to power air tools for car work and it's a special oil.

 

[Frito]

you might want to check the flashpoint before you do.

My bil has a big compressor he uses to power air tools for car work and it's a special oil.

Good point, 10w40 flashpoint is above 400 F. Mineral oil is 335 F. But most people use mineral oil for repurposed refrigerator compressors. I'll have to find out why.

 

[Compressor]

Why not just buy a small compressor from a hardware store?