"Clean Air" for Nitrox Tanks

[gxsr_sarge]

Reefraff - I applaud and greatly appreciate the time and effort you put into answering my questions!! I think I will also pick up the Oxygen Hacker's Companion. I'm far from blending my own gases (my wife thinks I may blow up our house) but I definitely would like to know what's involved. Thanks again!

 

[padiscubapro]

The fill station should be well maintained and clean but it isn’t necessary for it to be all shiny and new – most of this stuff is pretty heavy duty equipment and it isn’t uncommon for parts of it to be old. What matters most is the result which is why reading the test report is so important, though I personally avoid places that still wet-fill, no matter what their test reports say. If they don't check your C-card and look for hydro dates and VIP EOI stickers, you know they are sloppy with protocols and you should be nervous about what they're going to put inside your cylinder. Likewise, if they sell anything other than plain old air they should use a fill log, have a suitable analyzer available and insist that you use it when you pick up your fills.

If you're interested in this stuff, I recommend the previously mentioned Oxygen Hacker's Companion book and the ANDI Oxygen Handling and Gas Blending course student manual.

Wet fills are ok when done properly, and very bad when done incorrectly.. The only time I use them is when I blend trimix or fill Oxygen bottles.. I use very slow fill rates (I also have an extra cooling stage on by booster) but any extra help is always welcomed (even with slow fill rates it helps trimix blending alot)..

The problem with wet fills is if the filler does not purge the whips to insure they are dry.. If you purge the whips - this includes the bleed valves (and check for moisture), and connect before placing the tank in a bath its ok.. You also find small issues at time, like minor leaks in valves ect, that you would not have seen..

I deal alot with steel cylinders (including my own) and none of my regular customers who only get gas from me has even the slightest hint of rust on their cylinders..

FYI

Most Grade E and Modified Grade E specifications have been changed to allow 1000ppm of CO2 instead of 500ppm

 

[SDAnderson]

Wet fills are ok when done properly, and very bad when done incorrectly.. The only time I use them is when I blend trimix or fill Oxygen bottles.. I use very slow fill rates (I also have an extra cooling stage on by booster) but any extra help is always welcomed (even with slow fill rates it helps trimix blending alot)..

~

Most Grade E and Modified Grade E specifications have been changed to allow 1000ppm of CO2 instead of 500ppm

Done properly, wet fills won't hurt a cylinder. Done improperly, wet fills can damage or destroy them - or you. I disagree that any extra help is welcome, however; wet fills can't be justified based on a reasonable risk/reward ratio. I, too, have years of experience with tmx blending and have found that wet fills don't provide any significant advantage. The practice of wet filling should be stopped, it's old-school but so are J-valves and foot-long dive knives. Better to go slow and use a fan to keep the temperatures down, even when boosting He or O2.

The CGA created the Grade E standard and, as I noted in my post, they allow 1000 ppm of CO2. NAUI created the Modified Grade E standard and it's published on their website right now as 500 ppm of CO2. Nobody but the agency that created them has the right to modify these standards, if anybody has created something new and is calling it "Modified Grade E" they are...creating needless confusion. Besides, at 50 fathoms an extra 500 ppm of CO2 is getting to be a pretty heavy dose of something that can slip a great big shiv between the ribs of an otherwise good day of diving.

Peace and out.

 

[gr8fuldiverNC]

you should also try to find out whether air is tested before or after a filter change. i worked for a shop who posted the air tests, and they were always rated mod e. this surprised me giving the filthy, oily room the compressor was in, and the fact that the compressor was constantly being worked on in the same environment. then i found out that air samples were only taken after all the filters etc... had been freshly changed out. wonder if that makes a difference. to contrast, one highly rated tec shop i worked at tested air immediately before and after filter changes.