SCUBA tank as air compressor?

[Jack Ganssle]

SCUBA tanks have to be visually inspected once a year, which involves dumping all of the air from them. I have several here which are full, and will require an inspection in the Spring. My dad taught me to shudder at waste, so I wonder if it's possible to use these in the shop as a compressor? I'm thinking about putting a hose on the regulator's second stage, which would give a couple of hundred PSI. (Some catalog, I can't remember which, advertises a CO2 tank, smaller than a SCUBA tank, which they claim will drive several thousand nails per fill).

Question is: does anyone know of a hose that goes to a second stage on one end, and to a standard air fitting on the other?

[Steve Jenkins]

If you check in a dive shop you should be able to find a tire inflator that will connect to the lowpressure hose for your BC. You can remove the air chuck and replace it with a standard 1/4" quick connect. The only potential problem is that a lot of scuba regulators use 120psi or so as the low pressure which is a bit high for naill guns and such.

[Dan Ewalt]

I'm not a diver so can't say for sure what fitting will mate to the scuba gear but... If you go to a hydraulics (or similar place that sells hoses and fittings) they can make you a hose with any fittings you want. I use a nitrogen bottle for bike shock services and had a braided stainless hose made for that.

Dan

[Dave Bureau]

you can get a BDC quick disconnect fitting with pipe thread for your compressor hose. some regulators put out 160 psi on the low side though. I DO NOT recommend doing this with a regulator that you use for diving. It will pound the crap out of the high pressure seat and could cause failure. If you must, use an old regulator. Remember that your regulator is a life support system and should be treated as such. why dont you just go diving to use up the air? Just because the tank needs a visual dosen't mean the air is no good. If you are just looking to use up the last 500 psi in a tank, you wont get any mileage out of it and wont be worth it. Be safe.

Dave
Master Scuba Instructor
Equipment Tech.

[Cliff Rohrabacher]

Unless you are into diving with mixed gasses what is the waste?
It's just air right?

Inspections: "have to be"? or should be??
I thought it was every 5 years.
Let me check:............................................ ..................................

Yup it's mandatory every five years. That's for all compressed gas tanks.

The every year thing is merely a recommendation by the scuba industry and it's merely a "visual" inspection not a hydrostatic inspection.
And it is merely a recommendation not some mandatory rule.

[Dave Bureau]

Just the cost of filling the tank I guess.

[David Epperson]

I guess if you were framing a building in the middle of nowhere and didn't have a gas powered compressor......
But I would definitely rig up an additional reserve tank and step down regulator from the "low" side of the diving regulator before hooking up any air tools. IIRC a full tank is 80 Cu Ft - so figure how long that would last at your CFM usage rate. Might drive a few nails - but a die grinder or air ratchet using 4cfm or more and you're empty in 20 minutes or less. Work fast and don't make any mistakes.

[eric eaton]

I have been a Navy hardhat diver for 15 years. I will attempt to clear up a few things.

The connection to a scuba bottle is what is called a CGA 850. But most recognize them as a "scuba regulator". Most brands can be easily adjusted from 80 to 150 psi depending on the model. No low cost alternative really exists to convert a SCUBA bottle to low pressure.

There is only 80 CF of air in a standard SCUBA bottle filled to 3000 PSI, you will go through that fast. Plus the cost of a fill is usually $5 or more. Not really cost effective at all.

The real reason I would recommend against this as rapidly decompressing a cylinder causes lot's of unintended stress and also precipitates moisture in the cylinder which causes corrosion. Also if you take a cylinder to 0 PSI you start to introduce contaminants into the cylinder by a process called cold weep. The O-ring on the cylinder only works to seal the cylinder if there is pressure pushing against it.

We use SCUBA cylinders with a low pressure "wand" underwater when we need to fill lift bags and don't have ready access to surface air. These are kept separately from our "life support" bottles because of the contamination problem. We always keep at least 100 PSI in the cylinders regardless.

I hope this helps and good luck.

One Happy Navy SeaBee Diver

[Dave Bureau]

Unless you are into diving with mixed gasses what is the waste?
It's just air right?

Inspections: "have to be"? or should be??
I thought it was every 5 years.
Let me check:............................................ ..................................

Yup it's mandatory every five years. That's for all compressed gas tanks.

The every year thing is merely a recommendation by the scuba industry and it's merely a "visual" inspection not a hydrostatic inspection.
And it is merely a recommendation not some mandatory rule.

visuals are recommended only but most dive shops wont fill tanks without a visual sticker. (Job security)