High Pressure Nitrox

[kwinter]

Interesting question. According to one site http://www.diverdiscount.com/scubatanks.html
high pressure steel tanks are NOT recommended for nitrox diving. I guess they figure the higher pressure when doing partial pressure fills of O2 poses a greater risk of fire/explosion. I've never heard this before and neither has my LDS which does plenty of HP nitrox fills. Anyone care to comment?

Ken

 

[padiscubapro]

The tanks should be cleaned, the valves must be cleaned and compatible (are the valves they sell with it rated for nitrox??)

The problem with high pressure tanks when used for anything other than air, the blending process gets a bit more complicated.. first off if you local shop doesn't have a booster pump, they might not always be able to get the pressure of o2 thats required for fills, the air top off pressure (up to 3500 psi) is not possible for many stores.. finally Ideal gas laws start to screw up at this pressure so the person blending has to mix by real gas laws and order of mixing is important.. A store that is set up properly and has the properly trained staff, 3500psi fills are no problem..

a possible aside is if your shop isn't pumping really dry gas, the higher pressure the greater the amount of moisture will be condensing in the tank.. I wouldn't get gas from that type of store anyway..

Many people seem to be using genesis valves with HP tanks, theses must be cleaned and converted prior to use with nitrox(last time I checked).

 

[omar]

Ask them if they will fill an Al80 to 40%. If so then they do not have a valid argument based on the PP of O2.

A HP fill to 36% would need 668 (ideal) or 639 (real) psig of O2, topped with air to 3500.

A Al80 fill to 40% would need 724 (ideal) or 704 (real) psig of O2 topped with air to 3000.

If they do it with Al80 then it would be reasonable to do it with HP tanks as well.

No science just monkeyism

omar

 

[MikeFerrara]

We do nitrox fills in HP tanks all the time. LP is a little easier but it's not a big deal. I use a al 80 (3000 psi) for my 50% bottle. no problems there either. Diverdiscount knows even less than Rodale's. Learn about dive equipment and diving somewhere else.

 

[padiscubapro]

omar once bubbled...
Ask them if they will fill an Al80 to 40%. If so then they do not have a valid argument based on the PP of O2.

A HP fill to 36% would need 668 (ideal) or 639 (real) psig of O2, topped with air to 3500.

A Al80 fill to 40% would need 724 (ideal) or 704 (real) psig of O2 topped with air to 3000.

If they do it with Al80 then it would be reasonable to do it with HP tanks as well.

No science just monkeyism

omar

Omar thanks for the numbers I didn't have a chance to run them.. I was also thinking in terms of reblending instead of having to dump half a cylinder..

 

[kwinter]

Yeah, the diverdiscount comment sounded like bunk to me, too. I just wanted to verify it with the folks who have experience. My LDS has no problem with HP nitrox fills either. Around here, that's what most people use. Thanks for all your comments.

Ken