Running nitrox through my compressor

[abowie]

I currently do my own partial pressure nitrox blending. I predominantly make EAN60 or EAN80 for deco.

We have a 40m dive coming up and for this I feel EAN28 has significant advantages over air. Problem with EAN28 and partial pressure blending is that it's fiddly putting 18 bar of O2 into a tank. i'm looking for an easier solution.

I'm pretty impressed with the idea of a "Nitrox Stik" system as per Vance Harlow's "O2 hacker's companion" but I'm not so sure about running nitrox through my old Bauer compressor (full of oil).

It's not the filtration that worries me (I have 2 large filter stacks) but the risk of compressing EAN in a compressor running oil.

If you use a "Nitrox Stik" can you let me know what your approach was?

 

[DeepScuba]

PP and a good guage?

It's cheaper!

 

[Uncle Pug]

I've run O2 through my compressor for several years now... but I wouldn't do it with yours.

PP and a good digital gauge. I have a PSITronics high precision.. but they are expensive. Coleparmers are cheaper but not as accurate. Dwyer has just started selling a precision digital gauge that is economical.

 

[DeepScuba]

accurate enough! and with use and familiarity VERY accurate. I knwo guys that can use their thumb over the hole and get it within 0.5%

heheh

I'm kidding.

 

[Bob3]

I know guys that can use their thumb over the hole and get it within 0.5%

I suppose they can take a wiff of trimix & can tell the He content by how high the "Donald Duck factor" is, eh?

We'd run the Nitrox Stick into an old Mako with no problems. Tested for CO & the rest of the undesireables, no problems. Never went over 40% though

 

[abowie]

I suppose they can take a wiff of trimix & can tell the He content by how high the "Donald Duck factor" is, eh?

We'd run the Nitrox Stick into an old Mako with no problems. Tested for CO & the rest of the undesireables, no problems. Never went over 40% though

Thanks Bob.

To the other guys; I wasn't planning on BUYING a Nitrox Stik ($2K!!!), but building one ($100 if that). I have all the other bits; just need the pipe!

What worries me is blowing up my compressor.....

 

[Uncle Pug]

What worries me is blowing up my compressor.....

Some folks get away with it and some don't. Your original post said that your compressor was old. How are the rings? It isn't just blowing up your compressor that should concern you however... combustion and the introduction of CO into your breathing gas would be a concern as well. Filter well my friend and make sure that you have a moister filter ahead of your CO filter media as it doesn't like water.

 

[abowie]

Some folks get away with it and some don't. Your original post said that your compressor was old. How are the rings? It isn't just blowing up your compressor that should concern you however... combustion and the introduction of CO into your breathing gas would be a concern as well. Filter well my friend and make sure that you have a moister filter ahead of your CO filter media as it doesn't like water.

Sound advice.

The old girl was recently rebuilt prior to my buying it.

I have 2 inline filters. The first has silica in it; the second charcoal. I change the silica religiously every 3 hours run time (I use an old 24 hour timer with OFF set every 3 hours) at which point it is on average about 2/3 pink. The charcoal gets changed every 12 hours; it is a much bigger filter.

Some sources reckon that the 40% limit applies to compressors as well. what do the list think about that?

 

[chrisch]

Mix up some 32 or 36 and use that to get the elevated O2 by decanting a partial fill into your target tank then top off with air - this is much more accurate for small amounts of O2.
Problem solved - next please..

Chris

 

[abowie]

Mix up some 32 or 36 and use that to get the elevated O2 by decanting a partial fill into your target tank then top off with air - this is much more accurate for small amounts of O2.
Problem solved - next please..

Chris

Genius.

I fill one tank of one set of manifolded twins (manifold closed) with 50% to 200 bar. Easy.

I then open the manifold. Then I transfill half into the other set of twins, leaving me 50 bar of 50% in both sets of twins. Easier still.

Then top both sets of twins with air to 210 bar. Gives me EAN28 in 2 sets of twins, which is just what I want. It's a doddle.

Why the hell didn't I think of that?