Compressor As A Booster?

[OutlawCaver]

Has anyone ever tried to use a small compressor to boost gas pressure using tank gas as the input versus atmospheric air?

I suspect that a commercial grade gas regulator could provide sufficient mass flow just above atmospheric pressure.

For trimix or helium as input gases there may be seal leakage issues with conventional off the shelf compressors.

I surmise these compressors draw a variable volume as the pressure differences change. If this is the case a demand regulator could possibly be utilized.

Any thoughts are appreciated.

[FW]

I have seen adapters that allow O2 to be injected into the input, so you can use a standard SCUBA compressor to mix Nitrox. I have never seen it done with Trimix, though.

Anybody know of someone mixing trimix that way?

[curtschu]

Sorry to send you to another board but read this link on TDS

http://thedecostop.com/forums/showthread.php?t=15951&highlight=booster

It is for a thing called and Ommi Booster it is a gas recovery unit that alows you to scavage gas from cylinders such as Trimix. Im sure that it could also do straight He but i'm sure you know not to run O2 through a compressor. If you want to Continuos blend get the O2 hackers book. Great info there.

[Duncan Price]

Has anyone ever tried to use a small compressor to boost gas pressure using tank gas as the input versus atmospheric air?

I suspect that a commercial grade gas regulator could provide sufficient mass flow just above atmospheric pressure.

For trimix or helium as input gases there may be seal leakage issues with conventional off the shelf compressors.

I surmise these compressors draw a variable volume as the pressure differences change. If this is the case a demand regulator could possibly be utilized.

Any thoughts are appreciated.

There are two ways to do this:

The simple method is to connect the air intake to a large bladder (such as a trash bag) with a feed direct from the source cylinder regulated manually by a helper so as to keep the bladder from becoming emptied.

The better method is to use an old twin hose regulator to feed the intake directly. This only requires one person but be careful not to draw a vacuum on the donor tank.

Both argon, helium and normoxic trimix can be boosted by this means. Not reccommended for high ppO2 mixes.

[swadiver]

hey outlaw! call me regarding cav diving in august !

[MikeH]

I have used a compressor to boost trimix and straight helium. It works well. We used a very primitive method, though, that required your attention all the time while filling. We attached a 5' hose onto the air intake of the compressor(length of the hose is not important, neither is the hose actually). On the end of that, we attached a large bladder. A trash bag serves the same purpose. The bladder had 2 holes - one at each end. One end was duct taped to the hose, the other was duct taped over the top of a helium cylinder(or scuba cylinder if we were re-using trimix). Crack the valve on the cylinder enough to keep the bag inflated, but not 100% inflated so as to prevent a rupture. After a few minutes with the compressor running, you will figure out how wide open the valve needs to be to feed the compressor without causing an over or under pressure situation in the bladder.

It's primitive and redneck, but it worked! :-D

Mike

[tanto]

Here in Europe the "large bag" has been used to pump trimix for decades by cave divers, it's as easy as using a pressure reducer (like the welding regulator) and a micro-adjuster after that to adjust the flow so that it matches the gas taken by the compressor, it can go on for minutes unadjusted once regulated.
You cannot call it booster though, because the donor tank gas is brought to one atmosphere before being pumped again.
If you add a blender you can fill heliox easily.
The blender is also used to make nitrox.
If you have an helium-oxygen analizer you can fill trimix, triox, heliox, nitrox up to 40% oxygen easily with direct mixing. (but for heliox you still nee the bag).
The good thing about this system is that all tanks are returned completely empty to the supplier.