Nitrox Membranes

[san diego diver]

i have a small(6 cfm) RIX gasoline compressor. i want to set it up to pump nitrox.
i am looking for idea's or info on nitrox membranes that i can adapt to use with my compressor. i have been told that i need a low pressure compressor and a heating element. i want to hook a membrane in- line between the first and second stage(this is 150 lbs psi) and Grams law should take care of the heating problem. Right?
anyone out there have any suggestions?or recomendations?:scubadive

 

[cool_hardware52]

i have a small(6 cfm) RIX gasoline compressor. i want to set it up to pump nitrox.
i am looking for idea's or info on nitrox membranes that i can adapt to use with my compressor. i have been told that i need a low pressure compressor and a heating element. i want to hook a membrane in- line between the first and second stage(this is 150 lbs psi) and Grams law should take care of the heating problem. Right?
anyone out there have any suggestions?or recomendations?:scubadive

Unless you are going to be using this where there is no O2 available, continuous blending will be much cheaper and easier to set up.

Tobin

 

[san diego diver]

what about having o2 onboard. isn't that dangerous? i had considered using a blending stick but was told that it would cost as much in the long run

 

[cool_hardware52]

what about having o2 onboard. isn't that dangerous? i had considered using a blending stick but was told that it would cost as much in the long run

I don't know what your application is. Membranes are a practical solution for big boats, because they often either can't carry enough O2, or can't get it replenished. Membrane systems are far more expensive, and complex than continuous blending, or PP blending for that matter.

HP O2 has it's risk's, but when it's still in the supply bottle it's fairly safe. I'd say the biggest risk he supply bottle poses in most cases is having it fall over, or dropping it while moving them around. With continuous blending the pure HP O2 is in contact only with goods specificially designed for such use, i.e. the supply tank, the supply tank valve, and the regulator. The hazard with continuous blending is the scuba compressor. Using a Rix is will reduce that, but it is still a hazard.

Check with Nuvair. They are in Ventura, and sell membrane systems.

Good luck,


Tobin

 

[oxyhacker]

Interesting idea - you would be in effect using the 1st stage cylinder as an LP compressor and the 2nd and 3rd stage as an HP compressor?

One can think of a lot of possible objections - it may be difficult to adjust the mix without wasting too much gas, the natural balance of the compressor will be thrown off since you'll be dumping roughly half the gas between the 1st and second stage. Will this make the upper stages run hotter or cooler? Is the Rixes 130 psi 1st stage output enough - membranes usually operate at 200 psi or more? Hard to say. And you'll need good driers between the 1st and the membrane to avoid contaminating the membrane (which is all too easy to do). So my suspicion is that it probably is not going to work, but that it would really interesting to try it.

The big arguement for using a separate LP air supply is that (unless you have a big HP compressor and storage bank already) LP compressors are a lot cheaper than HP compressors (to say nothing of a lot cheaper to maintain) so it makes sense to use one for the LP air. By doing so in your case you would double the output and save wear and tear on the Rix, but lose the virtue of having one compact, portable unit.

The Rix SA6 is actually more like a 5 cfm compressor, so you would be outputting only 2-1/2 cfm at best if it does work, but that still ought to be enough to be worthwhile.

Might be an interesting experiment before you go any further to see how the compressor tolerates such use by putting a bleed valve/gauge between the 1st and second stage and try dumping about half the outut and see how well the compressor runs in terms of temperature, smoothness and output pressure.

You might want to also contact Bill Delp at DNAX systems and see what he has to say - they may have tried something similar.

i have a small(6 cfm) RIX gasoline compressor. i want to set it up to pump nitrox.
i am looking for idea's or info on nitrox membranes that i can adapt to use with my compressor. i have been told that i need a low pressure compressor and a heating element. i want to hook a membrane in- line between the first and second stage(this is 150 lbs psi) and Grams law should take care of the heating problem. Right?
anyone out there have any suggestions?or recomendations?:scubadive

 

[san diego diver]

i checked with nuvair and they are to expensive $11,000 if i want to go higher than 32% but they said if i only wanted to go 32% they MIGHT be able to get it down to 5,000 !! i think i am going to look into blending in a stick. i just ordered the oxy hackers handbook,and talked to my LDS(who is going out of the nitrox buissnes) and it looks like this is a more viable option.Rix did not appricieat my ideas about putting a membrane in between the first and second stages !!

 

[oxyhacker]

Definately the simplest, cheapest and most foolproof way to go, and a good way to gain some experience even if you should go on to a membrane later.

The membrane really doesn't make sense unless you either have a commercial application for it where it makes sense (that is to say, where it can earn its keep enough to pay for a commmercial system), or you are experienced enough with building such things, and a good enough scrounger, to build a system from scratch. The actual membrane isn't all that expensive, but the rest of the stuff adds up quick if you have to pay full price for it.

i think i am going to look into blending in a stick.

 

[san diego diver]

do you know where i can get the gauges i need to make the blending stick? or somepace that sells a blending unit?

 

[cool_hardware52]

do you know where i can get the gauges i need to make the blending stick? or somepace that sells a blending unit?

I'm not sure exactly what you mean by gauges. If you are looking for an O2 regulator, and maybe flow meters Ebay is your freind.

For Continuous blending you need a means to control / meter the O2 entering the mixer, and a means to measure the percentage O2.

The O2 regulator does the first, and a O2 analyzer, preferably with a remote sensor, does the second. All this is well presented in the Oxyhacker publication.

Look here to purchase a ready made stick. You will need to find a Global dealer, they don't sell direct. http://www.gmcscuba.com/main.php?content_url=ProductCatlog

Good luck,


Tobin

 

[oxyhacker]

Basically your choice is to buy a Nitrox Stick, from Global or others, for $1500 or so, or build your own, for about $25 (assuming you can find a suitable used regulator for $15 or so).

Neither price includes the O2 analyzer, which you must have in order to operate the mixer. You can buy one, for $200-400, or build one for about $100.

Just about any welding or medical regulator with adjustable output and made to go on a CGA 540 tank valve will work. The 540 is easy to spot because it has a big nut that screws onto the tank valve rather than a yoke. Welding regulators all have the CGA 540 connector, but med regs may have either the 540 or a yoke.

Welding O2 regulators usually have a wide enough range of adjustment that they will work on any size compressor, however some small medical regulators made to go on portable tanks may not have enough output for a continuous mixer, however these will usually not be usable anyhow since because they have the yoke connector.