Nitrox Fills

[MikeFerrara]

The most recent policy of thermo also states 40% is the max and doesn't recommend PP blending with thier valves

That may be true but a thermo manifold that you can't partial pressure blend through is about as useful as teets on a bull.

They should put that on their web site too.

 

[matt_unique]

Interesting what the websites list for the tanks. I don't have 02 cleaned gear/tanks for continuous (or premix) fills of 40% or less. The shops I use require 02 cleaning only for mix greater than 40% or if they do partial pressure filling.

--Matt

 

[padiscubapro]

Interesting what the websites list for the tanks. I don't have 02 cleaned gear/tanks for continuous (or premix) fills of 40% or less. The shops I use require 02 cleaning only for mix greater than 40% or if they do partial pressure filling.

--Matt

In the end a store can do whatever it wants, if something happens and the shop ignored manufacturer's recommendations they are on their own..

Mike,
at least the way thermo wrote their guidlines they didn't flat out prohibit PP blending.. The wording isn't as absolute as the 40% limit and oxygen clean requirements.

IMHO thermo valves turn on a bit too quickly for my taste, and it could be difficult to slowly pressurize a reg...

 

[Scubaguy62]

All are just fine to use.

A. Partial Pressure: Fill empty cylinder with pure oxygen to Xpsi and top off with filtered air from compressor or banked gas. Your scuba cylinder needs to be O2 clean because it is exposed to oxygen percentages above 40%.

B. Continuous Gas Blending: Oxygen and air are run through a compressor at percentages below 40% (Nitrox stick http://www.envirodive.com ) and through a filter system straight into your tank or bank cylinders.

Both are just as clean, but you do not need to oxygen clean your cylinder for B. Continuous Gas Blending because your cylinder is never exposed to Oxygen percentages above 40%.

Your cylinder does NOT become contaiminated by system B. if it has been oxygen cleaned for partial pressure filling.

My 2 AL80's are O2 clean, thus suitable for PP nitrox service. Only that 99% of the times, I have them filled using pre-mixed bank gases, prepared using B above. It does not mean that I can't switch back and forth, as I have before. Only that pre-mixed, banked gases are usually cheaper than PP blending (almost 1/2 as expensive).

It's important to know what the difference is between a cylinder being "nitrox ready," and "suitable for oxygen service." It's possible that the two are being misinterpreted.

 

[Aquawookie]

What is the difference in the grades of air; Grade B, Grade E, and Grade E+?

Different grades of air indicate the amount of impurities in the mixture.

Amoung these impurities are oil, water, hydrocarbons and C02. The fewer impurities (defined as parts per million PPM) there are, the higher the grade of air. In particular the level of hydrocarbons in the mix is important for a nitrox cylinder as it may become fuel for a fire.

Grade E Plus also known as Grade E Modified is the recommended minimum fill grade necessary to maintain O2 complience on cylinders selected for nitrox fills of 40% O2 or less.

Hope this helps. Good dives.
Paul.

 

[MikeFerrara]

In the end a store can do whatever it wants, if something happens and the shop ignored manufacturer's recommendations they are on their own..

Mike,
at least the way thermo wrote their guidlines they didn't flat out prohibit PP blending.. The wording isn't as absolute as the 40% limit and oxygen clean requirements.

IMHO thermo valves turn on a bit too quickly for my taste, and it could be difficult to slowly pressurize a reg...

I think PST tanks are shipped with thermo valves. I couldn't get in touch with my wife (who takes care of those kinds of details to check) but I was able to verify that diverite express ships them that way. Both tanks and valves are advertised as being O2 clean and O2 compatable. They also explain that they don't label them O2 serviced because they don't assemble the components in a clean room. Well...I don't either. Anyway here's the link

here

The PST site seems to be down but they have told us the same thing although I don't remember if I've ever seen it in writting.

 

[cth6]

My 2 AL80's are O2 clean, thus suitable for PP nitrox service. Only that 99% of the times, I have them filled using pre-mixed bank gases, prepared using B above. It does not mean that I can't switch back and forth, as I have before. Only that pre-mixed, banked gases are usually cheaper than PP blending (almost 1/2 as expensive).

It's important to know what the difference is between a cylinder being "nitrox ready," and "suitable for oxygen service." It's possible that the two are being misinterpreted.

So are you saying that using method B does not meet the O2 clean standard?

 

[jeffkruse2000]

If you have cleaned your cylinder for partial pressure filling, it will not be contaminated by also filling it with a continuos blending system afterwards.

You can use either system after your cylinder has been cleaned.

If your cylinder has NOT been cleaned you can only use the continuos blending system.

Curt, Continuous blending can be done with oily air. You can take even the oiliest dive compressor and increase the O2 (Stay under 40% please) on the intake. You will be putting out very oily Nitrox. I would not want to put pure O2 in that tank.

Jeff

 

[wedivebc]

Curt, Continuous blending can be done with oily air. You can take even the oiliest dive compressor and increase the O2 (Stay under 40% please) on the intake. You will be putting out very oily Nitrox. I would not want to put pure O2 in that tank.

Jeff

If I put O2 and air through this 'oily compressor' the PO2 of the mix at the last stage of the compressor would be about 80.0 for a 40% mix. If I were to PP blend this same tank I would add 49 bar of O2 (po2 49.0) then add air to it.
Wouldn't a po2 of 49.0 be less of a hazard than 80.0?
Not that I would want oily anything in my tanks.

 

[jeffkruse2000]

If I put O2 and air through this 'oily compressor' the PO2 of the mix at the last stage of the compressor would be about 80.0 for a 40% mix. If I were to PP blend this same tank I would add 49 bar of O2 (po2 49.0) then add air to it.
Wouldn't a po2 of 49.0 be less of a hazard than 80.0?
Not that I would want oily anything in my tanks.

No, its not the PPO2 thats the problem its the FO2.