Nitrox question

[quimby]

My LDS (Hollywooddivers in L.A.) blends Nitrox before filling the cylinders and he told me that because of that my cylinder will not be O2-clean. If I continue to have him fill my cylinder, does it matter? What if I go to another shop that fills partials? Also, my Atomic regulator manual says I can't go back and forth between nitrox and air. What happens if I do? Will my lungs spontaneously combust? HELP! Thanks!

Wait a minute from what I am reading he is saying that the shop is pumping premix less than 40percent, not partial pressure blending in the customers tank. Therefore not requiring the tank to be O2 clean but that others may not be doing the same thereby requiring the tank to be O2 cleaned. Which now that I reread is just what reefraff said in his post

if he has a clean system and blends by partial pressure to his banks, his gas should be clean and wouldnt effect your tanks.. many LDS use membrane systems without the proper filtration and can put contaminated gas into the system

I havent seen that and one reason is that if someone is spending the money on a membrane system, he usually gets fairly anal about his gases or he spends buckets of money replacing his lp system and membranes as well as his hp system and even lds's have more sense than that.

Also, my Atomic regulator manual says I can't go back and forth between nitrox and air. What happens if I do? Will my lungs spontaneously combust? HELP! Thanks

Only if you gargle with crude oil before a nitrox dive and suck in nitrox fast enough to cause excessive heat from adiabatic compression. But the real answer is again what reefraff referred to in his post.

 

[jextract]

OK, not to beat this dead horse into a pulp, but if I get my fills at a shop that can provide hyperfiltered/O2-compatible air fills, THEN am I safe switching between air and Nitrox on the same reg?

Thanks in advance, and sorry if these questions seem elementary to you more experienced folk.

 

[quimby]

OK, not to beat this dead horse into a pulp, but if I get my fills at a shop that can provide hyperfiltered/O2-compatible air fills, THEN am I safe switching between air and Nitrox on the same reg

mas important you understand the why, the reason for the "questions" about air quality is really bad air is going to leave hydrocarbons in your regulator hence the potential problem on nitrox. Now to get really bad air, I dont think you will have any problems stateside but out of the country all bets are off.
As said before the generally accepted below 40percent same diff especially with regular service on the reg and vip.
If you do a search on nitrox clean or nitrox regulators youll be busy and confused for a long time and find that a lot of preaching goes on

 

[padiscubapro]

I havent seen that and one reason is that if someone is spending the money on a membrane system, he usually gets fairly anal about his gases or he spends buckets of money replacing his lp system and membranes as well as his hp system and even lds's have more sense than that.
.

the biggest propblem is after the HP compressor.. The gas should be clean going into the membrane otherwise it will fail prematurely, but if the shop doesnt do enough POST filtration of the HP gass there is oil in the gas the diver uses..

UBS/DNAX (a manufactre of membrane systems) allows 5 mg/m3 of condensing hydrocarbons, that is no better than grade e gas..

The oxygen standard is .1 mg/m3 thats 50 times cleaner..

As I stated earlier in the thread the BIGGEST concern is not the diver breathing off the reg rather when the diver turns the cylinder valve open..

The heat generated by air is pretty high going from ambient up to tank pressure as the o2 content climbs the heat climbs at a much greater rate, the higher the temp the greater the risk of SOME type of combustion it doesnt have to be a fire, you might not even know it happened.. You first clue might be as mnor as having mild co symptoms (cherry red nail beds)

I have serviced regs that people used for nitrox and complained the IP was creeping, reg "burbs" gas when not being used ect... in many of these cases the HP seats had obvious signs of partial combustion.
I have seen other regs that worked fine that had obvious partial combustion at one point, so it is more common than many are willing to admit at the fear of losing some sales..

Bottom line if you are going to use nitrox get gas thats oxygen compatible (I dont care how the nitox is made) and dedicate the regs, its better to be safe than sorry..

 

[quimby]

I have seen other regs that worked fine that had obvious partial combustion at one point, so it is more common than many are willing to admit at the fear of losing some sales..

Interesting I have seen one and that was given a shot of straight o2. I have never had anyone make that comment and have discussed this at length with quite a few people and the only "combustion" evidence was in units as in the one I referred to and none hit with less than 50percent.

 

[padiscubapro]

Interesting I have seen one and that was given a shot of straight o2. I have never had anyone make that comment and have discussed this at length with quite a few people and the only "combustion" evidence was in units as in the one I referred to and none hit with less than 50percent.

If you know what to look for there are lots of minor things to look for that can be EASILY overlooked... When its blatent its easily spotted..
As more regs are "nitrox ready" out of the box this has to become of greater concern.. the most common o-ring used for nitrox ready regs is Viton, they are durable as hell and are oxygen compatible, however, if an fuel is present on it and it does combust even slightly the gas produced by a burnt viton oring is toxic.. The places too look for problems are in the HP section of the first stage problems in the second is very unlikely.. another point to examine is the HP swivel on your spg, this is a common point of high temperature luckily the HP hose is restricted.
I am not saying that lots and lots of dives go off without a hitch, they do, but even if its 1 in 10000, if you are that 1 your life could be endangered. Is your life worth a few hundred extra dollars??

I know My life is worth more than the price of a regulator or overhaul..

The longer the reg is used with a questionable source the higher the contaminate level, the overall risk is low but it does happen.. The risk is highest for the guy filling the tanks.. I personally will only fill tanks (with enriched air) that are o2 clean even when they come from my banks.

Not only does this increase safety for me it also prevents another accident from happening, someone with a contaminated tank flushing gas back into my system potentially contaminating my whips... (pressure in tank higher than at my manifold - If I forgot to turn on the source gas to the manifold)

 

[WarmWaterDiver]

I follow the industrial standards as briefly mentioned by padiscubapro, based on my industrial experience. All the rest of scuba training and tech diving training seems to focus a lot on informed risk management, except now these discussions regarding 40% O2 or less mixtures it appears. A grizzled industrial worker once informed me in my younger days how he had seen a 80 PSIG air piping header "decoked" and glowing cherry red throughout a manufacturing plant due to an attempt to install extensions to in-service piping with a compressed air atmosphere and laydown of compressor lubricating oils in the system. The very nature of lubricating oils are to form tenacious films, and this was not a "high" pressure system nor an enriched O2 content system. These type modifications ("hot taps") are stringently avoided in industry for compressed air systems (even after passing through filtration and dessicants), but are routinely used for high pressure hydrocarbon, high pressure hydrogen, etc. safely as there is an exclusion of O2 for these services. If I'm going to be a statistic, I want to be an example of the large number referenced in such (like 10,000) and not the small number (as in one in), but each individual must make their own choices.

 

[Hollywoodivers]

I Hope that all this technical info has cleared up the now dead thread about membrane vs dedicating a cylinder and reg.....
I breathe air and nitrox on a regualar basis from the same system I use to fill my customers tanks. You lungs will NOT explode ...I promise, as I am a living lab experiment . If you do dedicate a cylinder be sure you do not pass it off as oxygen clean after it leaves our shop. It will not be.
We use a Bauer ( german made ) filter system and compressor backed up with a UBS nitrox membrane system which has it's own tower filter as well. Both of these systems were installed by manufacturer technicians.
These machines exceed the industry standard for breathing air/ less than 40 percent o2. And at a cost of nearly 25000.00 for the two compressors and the storage system they have been worth every penny.
We do keep 02 clean bottles in our shop for stage decompression needs should you ever need to rent one.These are filled from an o2 clean system and those bottles are not available for all to rent. Certification in deco procedures and advanced nitrox is required to use this equipment.
Thanks to all those who replied to this thread. Sorry I did not see it sooner.