First-Time blending of my own Nitrox...Amateur Here...Looking for your Thoughts!!!

[bakodiver391]

To answer just one of your questions, the elevated argon concentration will not be an issue. We have been running medical O2 concentrators and banking O2 for PP blending for several years now. The manufacturer specifically warns against using this gas for diving purposes, but there is a long history of success, and frankly, in a remote location, we simply have no other choice, as we cannot carry enough O2 for long expeditions. A lot of our diving is CCR, where you would expect the argon to be a problem if anywhere (higher fraction of narcotic argon at depth, increased tissue uptake) and to date it has been a non-issue.

 

[Doc Harry]

Get some professional training before you kill yourself. Take a gas blender course.

Best case scenario: Find a instructor who can show you large, commercial compressor/mixing/banking system, but who can also take you to a small (personal) compressor system with partial-pressure blending and continuous blending systems.

 

[Pyrotrons]

My equipment has arrived!! It's ALL in excellent condition, I'm really excited.

The Honda GC160 engine-driven HP compressor started on the third pull, the gentleman that had it stored obviously drained the gas before it was stored. It's well maintained. Reasonably clean. Full of oil.

Neither the HP compressor, hoses, nor output filter, exploded at 3,000PSI. Which is good. I value my reputation with the neighbor's.

I sifted through the manual of the flamethrower that this system was designed to pressurize. I'd give it a high likelihood that the main shaft coupling between the gas engine and the HP air compressor is of tapered design. This is a little disappointing, as I would like to retrofit an electric motor to drive the compressor instead of the gas engine. I don't know if the lathe I have access to holds the kind of precision necessary to make a suitable shaft coupler.

The Invacare O2 concentrator works GREAT. I put a piece of Tygon tubing on the output, cranked the O2 up, and set fire to the end of the tubing. You did WHAT???? Awww... you think I'm halfway pulling that hammer back on a six-gun don't you : ) SO CUTE!! Thing is, I prefer semi-automatic, DA/SA, and a minimum of 15 rounds of 9mm. (EDIT: This comment is specifically directed to revolver-guy in the previous page).

The flame front progressed at about 2 inches per second up the Tygon tubing, to the front of the Invacare unit, where I madly scrambled to unplug the machine. Got you didn't I. Seriously, it was only a little slower than I expected.

I haven't played with Oxygen much, but as far as oxidizers go it's not too terribly bad. Don't get me wrong... It's nothing I'd recommend to an inexperienced backyard chemist. But it's definitely nothing like some of the other oxidizers that I have experience with. I'm sure it gets more serious with the liquid phase (LOX) due to the higher density/quantity, but observing it's activity with room-temperature fuels (including "Slim Jim" beef jerky), I doubt that it's hypergolic with fuels of lower reactivity at room temp. Oh wait... revolver guy, did you you again assume that I was just some know-nothing dude with new scuba mixing equipment? It's ok. I don't blame you revolver guy.

The Invacare O2 compressor wouldn't turn on at first. Found a bad pressure switch that turns the system on when it senses low-pressure input O2. I shorted out the wires going to the bad switch (with good input O2 flowing of course) and it came right on. Neither the NC nor the NO contacts changed when I beat on the device with a screwdriver. Other than the switch that went bad...it's an incredibly well designed and manufactured system. And VERY simple, there's truly nothing to it (parts count-wise) other than precision design and machining. I'd like to know how they do the high-pressure (oil-less) seals in their HP pump stages. I'm guessing pressure-fit precision machined Teflon in SS cylinders. The crankshafts each look like they could each withstand tens of thousands of pounds of tension and compression... some serious force there. Trust me you'll love the pictures when I post them tomorrow hopefully. It's gorgeous.

I figure that since the O2 compressor is sucking in (on average) about 2 Liters per minute of O2, the output at 2,000PSI would be 2L/2000 = 1mL per minute. Pretty low. This seemed to coincide with how long it took to get the fill hose up to 2kPSI. This thing hums along nearly silently though, I'd have no problem letting it pump a tank overnight in the shop.

The compressor doesn't quite make it to 2,000PSI. More like 1750... but it can't get past that? Not really a problem, however, I bet there's a loose compression fitting somewhere. There must be a very small leak. The hour meter shows 52 hours, nearly brand new.

I can't remember off the bat who makes my HP compressor output filter, but it's just a typical cylinder filter. Unscrew the cap, dump out old media, pour in new media. I have a LOT of research to do on what types of media to use. I'm immediately concerned about CO and hydrocarbons due to the ridiculously close proximity of engine exhaust. Water in my tanks would be my next concern.

Thanks to ALL of you, including revolver-guy, for your constructive input.

I'll also add, that I don't intend to do any mixing in the near term. Too much stuff there that I'm unaware of right now. Fantasizing over the various methods however, my options appear to be either partial pressure or mass fraction. I'm very much liking the mass fraction approach... there are some incredibly accurate scales available. I would probably get two, stack them on top of each other, put the recipient tank on top of both, connect the whip, then zero both scales. This would give a redundant real-time display of O2 or Air mass. Then I'd directly measure the final mix with an O2 meter or two.

Thank you to those who those User's who have PM'ed me with valuable advice, encouragement, and know-how...

 

[maniago]

Sounds like fun! The compressor is a bit of a downer pressure wise. If its supposed to go up to 3000 psi, you'll be hearing a large hiss even when its on if you have a connection leak. If its designed for low pressure, you have a conundrum - its too low to use for scuba, which I'm sure you know. I'll be interested in more on what you do there.

You also mention a high pressure mixer of some sort. What's that (mfg etal)?

Pics pics pics please.

Cheers!

 

[Wookie]

I sifted through the manual of the flamethrower that this system was designed to pressurize. I'd give it a high likelihood that the main shaft coupling between the gas engine and the HP air compressor is of tapered design. This is a little disappointing, as I would like to retrofit an electric motor to drive the compressor instead of the gas engine. I don't know if the lathe I have access to holds the kind of precision necessary to make a suitable shaft coupler.

Most folks drive their compressors with belts. If you are handy, it isn't hard to make up a frame that holds the motor and pump attached with belts. If you really like direct drive, try Lovejoy couplers. You can buy either end in tapered, straight, woodruff or square key, whatever your 2 ends are and mate them together. Lovejoy couplers give the extra added advantage of not requiring quite as precise of an alignment as other types of couplers.

 

[Peter_C]

So where are the pictures? As Frank above suggested most electric compressors are belt driven and should be fairly easy to set up. Especially if the compressor was offered in an electric version.

What kind of filtration did it come with?

I believe some folks are getting confused on "which" compressor is only going to 1750 psi. Depending on your storage bottle for oxygen I might be inclined to only pump to 1,000-1,500 psi. Lower pressures are safer. Continuous blending is the safest, and with the Oxyhacker book a pretty simple system to setup.

 

[maniago]

Continuous blending is the safest, and with the Oxyhacker book a pretty simple system to setup.

Easy there cowboy. This is only true with compressors and gear that are listed as O2 pumpable-safe per the mfg. Beyond that, youre a test pilot.

BTW did you read that his compressor is for a Vietnam era flame thrower ala 1966?

 

[Doc Harry]

Easy there cowboy. This is only true with compressors and gear that are listed as O2 pumpable-safe per the mfg. Beyond that, youre a test pilot.

Not quite true, either.

If you read the books and listen to the "Experts," then your statement is true.

But you're not a test pilot either. There have been several decades of home brewers safely running compressors and doing CB to 40%, even when the manufacturer does not approve of mixes above 21%.

I routinely fill my Nitrox bank to 4,500 PSI with EAN 32.

Can someone provide an example of a compressor that started on fire while doing CB?

EVER?

 

[maniago]

Can someone provide an example of a compressor that started on fire while doing CB?

EVER?

Fire no idea. Blow up, yes. I have what's left of one integrated in my compressor setup. Seriously Doc don't make blanket statments about all compressors being ok to do whatever with. That's just flat irresponsible on a public forum like this. Even the Oxyhack book notes its an unknown risk.

If you (whomever is reading this) own a compressor, do your homework on your setup and understand what the mfg engineers say the gear you have is good for. If you are outside the said parameters and it goes south, thats your fault - noone elses. Of course, make sure your insurance company knows you are operating outside the box - they will be happy to deny your wife's claim.

 

[Pyrotrons]

I'm glad there's interest in pictures, hang tight, this and model numbers, mechanical diagrams of the compressor, everything will be here before the end of this day at midnight CST.

SCUBA Output Filter on this Honda GC160 Gasoline-Engine-Driven AIR compressor designed for flamethrower fluid pressurization in 1977:

It's a gray cylinder filter that's about 2.5" diameter x 14" long, gray color, black faceplate, 3,000PSI, with screw-on end cap to change out filter media. More info soon... but you can find this filter online somewhere, along with media. It's relatively common I think.

In series with the HP fill hose, separate from this filter, is a nicely machined knurled brass high-pressure rated "container" with a sight glass. A small white circle of Relative Humidity (RH) and Carbon-Monoxide (CO) indicating material is behind the sight glass viewing window. I believe the device is made by Aerocon Systems (.com). However... the CO filter they sell is specified to indicate CO concentrations above 100ppm. THAT, I do not understand. That's 10X the CO I'd deem acceptable to breathe at high pressure, I wouldn't touch this if I was them, but what do I know. I think some of their equipment is for SCBA's (not SCUBA's), so at 1ATM perhaps the CO toxicity threshold is 100ppm.

Aerocon Systems

The RH indication would be the only useful one for this... which is nice.

Converting the gasoline-engine driven AIR compressor to electric drive:

The shaft end of the gas-engine-driven AIR compressor I think is a female taper that is INSIDE the compressor. I could be wrong... I will post the diagram along with the pictures soon, but I don't think I'll be able to just hang a pulley on it. Thanks to Wookie for the Lovejoy coupler source and recommendation.

Invacare Medical O2 compressor not making 2,000PSI:

It's about 250PSI shy of 2000, not really a problem, however it would run forever if I turned it on and left it. To turn it off I just yank one wire going to the 2,000PSI pressure switch (which is configured via its N.C...normally closed...contacts).

Any recommendations on how to find a small HP O2 leak? O2 analyzer...but how to get O2 to its sensor?

I'm sure it would be easy to "sniff" around with a small glowing ember from a recently lit match, but I'd rather die flying.