Nitrox Stick

[ontario-diver]

I have a friend who is a dive store owner and is looking at bringing Nitrox in. He is deciding on the system he wants to use.

I was looking for pros and cons on using a Nitrox Stick

Thanks

Brian

 

[rstofer]

Try the Equipment->Cmprs/Boosters/Blending Systems forum.

Richard

 

[DA Aquamaster]

Contact one of the mods and they can move it for you.

Using a stick avoids the need for O2 cleaning of nitrox tanks under 40% as is the case with partial pressure blending where every tank is expsosed to 100% O2. And it is also cheaper than a membrane system.

However it is a bit of a pain to set up and run on a single tank basis so it works best if you fill several tanks at once or if you fill a cascade system and then fill individual tanks from the bank which in turn limits your bank to a standard mixe like 30%, 32% or 36%. Lower percentage mixes then require you to start with a higher percentage mix in the bank and then top the tank off with air to get the desired lower percentage. That may or may not be a limitation depending where your are and what mixes are wanted and used locally.

Also, 40% is the upper limit for running nitrox through a compressor, so higher percentage deco mixes will still require partial presure blending.

 

[ontario-diver]

Thanks for moving the thread!

DA_Aquamaster---Its just a small shop, not many tanks being filled at once---Thanks for your reponse

 

[oly5050user]

small shop---partial pressure method..some will also say stick method shortens compressor life..if a bank available make a bank of 50% and mix with that..will need a haskell/booster pump to use gas efficiently..

 

[Doc Harry]

I have compressor for home use and only fill a couple of tanks at a time. Although some state that there are disadvantages to the Nitrox strick when filling just a few tanks at a time, I personally don't see it. It works just fine. But then again, all I use is EAN 32 and do not mix anything over 40%.

The only disadvantage I see for a Nitrox stick would be the need to bleed your lines and filters if you you need to switch gasses between fills, e.g., EAN 32 then air then EAN 38 etc. If you bank EAN 40 then you can do partial pressure blending with EAN 40 and air to get other Nitrox blends.

Compare these disadvantages with those of oxygen cleaning everything and the inherent dangers of partial-pressure blending with 100% oxygen. How are you going to guarantee that your client's tanks are oxygen clean before you start filling them with 100% oxygen?

If I ran a commercial operation, I would be terrified to do any partial-pressure blending with 100% oxygen on any cylinder that didn't belong to me.

 

[DA Aquamaster]

I have a 3.5 SCFM compressor and the lines and filter only take up about 6 cu ft of volume at 3500 psi, and obviously a lot less at low pressure.

Consequently, if filling a tank via stick, it does not take long to have the O2 rich mix flowing through entire sytem to the fill whip if the system is depressurized. But what ever size compressor and filter stack you have, you need to let the compressor run long enough for the stick mixed nitrox displace all the air in the system before you start filling the tank.

Its more efficient to just set things up once and then fill several tanks or a cascade system. 50% is a bit too much for most compressors, so I'd limit the bank to 40%, then top with air (which also lets you get a lot more full fills out of the cascade system before you have to top it off again.) Or if 32% is by far the most popular mix, just fill your bank with it and be done with it.

Even with that consideration, it is whole lot easier than PP blending and avoids the need for a booster to use the vast majority of your O2 in the supply tank. For best results you need to use a proper metering valve for the O2 and if you have one be sure it does not get abused (cranked down tight, etc) if you want it to remain accurate and easy to use.