O2 cleaning question

[Tortuga68]

I stand to be corrected but I believe hyperfiltered Grade E air or modified Grade E is what you want to put into your O2 clean cylinders

http://www.fillexpress.com/library/gasquality.shtml

 

[Doc Harry]

So my question is why has this never been an issue when diving with air below 130' where the PP of the O2 is 14.7 psi (1ATM) or greater? Or have we just been lucky all these years?

The ppO2 while blending is anywhere from 250 psi to 2,400 psi, that why the equipment has to O2 clean. (Tough to find a O2 cylinder at more than 2,200 to 2,400 psi.)

Oxygen at 14.7 psi ain't nothing.

 

[Tortuga68]

Isn't that fill pressure not partial pressure?

 

[Doc Harry]

Isn't that fill pressure not partial pressure?

When FO2=1.0 then pp = fill pressure

Since we're dealing with 100% O2 during pp filling, then the pp equals the fill pressure. At least initially, until you start topping off with another gas.

And while our bodies are most concerned with the ppO2, the equipment is most concerned with total pressure.

 

[Tortuga68]

If you're doing a 100% O2 fill yes... but if you're doing say an EAN50 blend then no

Eh, that's probably what you meant anyway, it's too early in the morning to be thinking about this

 

[Doc Harry]

Yeah, you're right.

A lot of time you start out by titrating in some 100% oxygen and then top off with air to make your mix. So at least in the beginning you've got 100% O2 at 2,200 psi in the main O2 cylinder and you adding SLOWLY to your dive cylinder to a pre-determined total pressure.

 

[LakeCountyDiver]

Yep. In fact I think I paid $35 extra to use EAN36 when diving the ex-HMAS Brisbane last month... My buddy and I did 4 dives over 2 days, so there's $280 for gas alone, on top of the dive/boat fees which were $640 all up. And we had our own gear apart from tanks. SO including petrol for the drive it was about $500 each for 4 dives. No wonder I don't dive in Australia much - I could do a week of diving in the Philippines for the same price

Still, at least it's not helium

Dude is this in U.S. dollars or another form of currency? There is no way to afford that kind of diving.

 

[Tortuga68]

It's in AUD but given the current exchange rate, it's pretty much the same in USD

I don't live in Australia any more, so it's my annual indulgence when I go home for a visit

 

[DaleC]

Some of you guys are getting a little confused by all the different numbers and abbreviations.

Oxygen itself does not explode or catch fire. It does however, cause anything that does explode or catch fire to do so much much more dramatically. That is why one needs to O2 clean when filling with rich mixes.

If there were something (like hydrocarbons) in the tank or valve that could ignite due to the high heat generated by compressing gas, the O2 would cause a very big boo boo indeed.

For partial pressure blending this is the case.

For filling off a bank with under 40%, the O2 is generally thought to be diluted enough to not create the same potential for disaster.

 

[fire_diver]

FYI, anything will burn under the right conditions. Steel under high enough pressure oxygen will spontaneously combust. Titanium, at elevated O2 levels in the pressures seen from scuba tanks will combust.