Air Cleanliness and Continuous Blending NITROX

[Waterskier1]

I’m looking for additional information. I have read, and think I understand the reason for O2 cleaning; both for tanks and lines, as well as the air in them. As I understand it, it is mostly required when the partial pressure of 02 will exceed 40%.

As I understand the requirement of really clean air, it has to do with possible organic particles that could be a source of ignition if >40% O2 come in contact with them. What I have read usually applies to partial pressure blending. In that case, extra filtration on the air that will be mixed is required.

I also have read that if you use continuous blending, that O2 cleaning (better than Grade E) is not as (if at all) important. So, my question concerns setting up a continuous blending NITROX compressor system (<40% O2). As I understand it, the filtration is after the compressor final stage (besides some minor filters on the input to the compressor). If that is the case, is the extra filtration still necessary for continuous blended NITROX? After all, the O2 has already been mixed, and compressed. The only reason I can see to super filter (better than Grade E) is to maintain the tank&#8217;s O2 cleanliness in case they ever are subjected to >40% O2. If never use anything but regular (Grade E) air or my own CB NITROX, do I have to hyper filter my NITROX and maintain my tanks O2 clean? I think I&#8217;m missing something here. If a compressor manufacturer rates his compressor as safe for up to 40% O2, is it necessary to filter the output of it better than Grade E. If not, why are so many adding extra (over Grade E) filtration to their compressors?

I&#8217;m looking to purchase a portable compressor, and would like to get one that I can eventually add a mixing stick for NITROX Continuous Blending. I&#8217;m getting confused with compressor requirements, filtering requirements, and O2 cleanliness. Can someone help me sort all this out, so I don&#8217;t purchase the wrong thing, or blow something up :11::no

 

[pescador775]

No. The reason for confusion is that hyper air is over hyped. Go ahead with your plans.

If that is the case, is the extra filtration still necessary for continuous blended NITROX?

 

[rcontrera]

Pesky is right ... there is a lot of hype about hyper filtering air.

Yes, the air must be VERY clean when partial pressure blending. However, if you make your nitrox before it hits the compressor, then you don't have as much to worry about.

In the late 80s/early 90s when Nitrox was just coming out in dive shops, times started really getting tough in the diving industry!! Nitrox was written up in trade journals as a good way to sell new things to our existing customer base of old time divers.

Seems that "voodoo gas" turned out to be good stuff so it stayed around! Now, with more and more people buying their own compressors, "hyperfilters" are the latest add on sales.

Yes, adding more filters will make air a bit cleaner after it has gone through the compressor. But, if you are planning on blending your nitrox before the compressor, the only thing the added filters may do is change the O2 percentage a bit (activated carbon scavenges oxygen a tiny amount).

I would love to sell you extra filtration, but if you are buying a new compressor that is rated to pump nitrox (all ColtriSub compressors are rated to 40% at 3000 psi), then the installed filtration should be all that you need provided you change them and your oil regularly.

 

[Waterskier1]

Thanks Pesky and Ron.

Ron, what are the Bauer Jr, Jr II, and Oceanus rate for?

<40% @ 3000 psi is good for me.

 

[rcontrera]

The Junior is no longer made, but neither the Junior II nor the Oceanus are rated for Nitrox officially by Bauer. However, there are lots of people that pump it with no problems.

Coltri Sub was the first to rate all their compressors for up to 40% at 3000 PSI since they also build Nitrox generators and membrane systems.

 

[vladimir]

As I understand the requirement of really clean air, it has to do with possible organic particles that could be a source of ignition if <40% O2 come in contact with them.

Do you mean greater than (>40%)?

The only reason I can see to super filter (better than Grade E) is to maintain the tank&#8217;s O2 cleanliness in case they ever are subjected to <40% O2.

Do you mean greater than (>40%)?

I'm not nitpicking, just checking.

 

[Surface Tension]

I've been pumping up to 38% (usually 34) through my Junior II for a couple of years now and it hasn't skipped a beat. I do have a larger filter tower than the stock PO though, just so I don't have to swap out filters every 15 tanks. I also run a synthetic compressor oil, Chemlube.

 

[Waterskier1]

Do you mean greater than (>40%)?

Do you mean greater than (>40%)?

I'm not nitpicking, just checking.

Yes you are right. I made the changes.

Thank you.

 

[stevewirl]

we use a coltri sub compressor for pp mixing and a larger coltri sub for CB never had a problem with either . both are portable .

cleaner gas ???? deepends . if your suppling to other s use the extra stack filters if only for personall use . no need . no need to have O2 cleaned if your CB your nitrox .

But as the saying says : better safe that sorry . but there has never been an incident with nitrox blending in ireland .

 

[rcontrera]

I forgot to mention this, but one thing to note on your compressor when pumping oxygen enriched air ... change your oil more often.

Oxygen will increase the degradation of almost everything "soft" in the system (seals, gaskets, oil, etc.) so the best thing you can do for your compressor is to use clean high grade synthetic oil. Also, the 455 oil that is food grade (the stuff recommended for machines pumping Nitrox), has an increased affinity for water. Changing early keeps water buildup from happening.

The ColtriSub owner's manual for the small portable (MCH-6) calls for changing oil at 50 hours. If you cut that down to 25 hours, you probably won't have to use the 100 hour service kit until around 300 hours.