Diving on nitrox and air with the same regs?

[Charlie99]

I found a bunch of posts on the June 2000 incident in San Diego.

O2 tank explodes - San Diego 6-3-00 - rec.scuba | Google Groups is a post by GUE instructor MHK.

But as to the facts, He was working with a bunch of open water students and
was planning on doing 5 very shallow dives with different students during
the day. He wasn't even taking the gas in the water, he just wanted to
breathe it as an extra measure of protection during SIT's. He cranked on
the bottle while leaning on the back of his truck. His arm was leaning on
the 1st stage and when he opened the valve it ignited. He was using the
Atomic T1/T2 and swears that it was 02 cleaned. The tank ( AL 40 ) was in
current hydro.


His wetsuit caught on fire and by the time he was able to get the flames
extinguished he has suffered some bad burns.

 

[charlesml3]

The problem is the rapid pressurization within the reg when you turn on the tank valve.

Still doesn't make sense. Sure, when you open the tank valve you get the quick "hiss" as the hoses pressurize. I just don't think that generates heat. If anything, it gets cold. I was in a dive shop once when a burst disk went. We had to just wait for the tank to bleed off and after a few minutes the whole top of the tank was frosty with ice.

How much gas moves from the tank to the reg when the valve is first opened? A tiny fraction of a cubic foot? I seriously doubt it's enough over long enough time to flash some fuel source.

-Charles

 

[JeffG]

I just don't think that generates heat. If anything, it gets cold.

The "thing" that loses pressure gets colder, the "thing" that has a pressure increase gets warmer.

Physics.

The tank valve gets colder, whereas the the first stage gets warmer.

 

[Web Monkey]

I ask this because there seems to be the idea that once it is O2 clean for 100% that you can't use it for regular air. This is something that I don't buy

Once it's O2 Clean you need to use it only with hyperfiltered air (Grade E Modified) or mixes made with the above.

If you use it with anything else, it's no longer O2 clean and the chances of killing or injuring the fill guy may increase depending on the actual contaminants.

Terry

 

[crpntr133]

Never mind, I think your talking tank I'm not. I just wanted to see what the opinion was.

 

[joey46987]

I appreciate all of the posts about this topic. I do have an Atomic SS1 that says that you shouldnt switch back and forth from air to nitrox and back.

"What about Nitrox?

All of our regulators are factory cleaned and tested with oxygen compatible air. They are built with oxygen compatible components and lubricants where necessary, and as a system, are ready to use with EAN Nitrox to a maximum concentration of 40% oxygen up to 3500 PSI. Our M1 is designed for use up to 50% oxygen with no special cleaning and up to 80% maintained clean and dedicated to oxygen/oxygen compatible air service.

Can I switch back and forth between air and Nitrox?

No, we do not recommend it. There are different cleaning and purity standards for air and Nitrox. Using standard compressed air with your regulator could introduce dirt or hydrocarbon contaminants into your regulator that could possibly initiate an ignition (fire) in your system. Oxygen enriched mixes can be highly combustible under the right conditions. It is always better to be safe then sorry."

this is right from the Atomic website. does anyone dive with an SS1 that uses nitrox?

 

[Web Monkey]

No, we do not recommend it. There are different cleaning and purity standards for air and Nitrox. Using standard compressed air with your regulator could introduce dirt or hydrocarbon contaminants into your regulator that could possibly initiate an ignition (fire) in your system. Oxygen enriched mixes can be highly combustible under the right conditions. It is always better to be safe then sorry."

this is right from the Atomic website. does anyone dive with an SS1 that uses nitrox?

I have an SS1, 2 M1's and a Z1 and dive Nitrox as well as hyperfiltered air all the time.

To maintain your regulator in it's O2 compatible state, you need to only use mixes created with O2 compatible air. This is "Grade E Modified" or "hyperfiltered". It is the same air used to create Nitrox when mixed with oxygen.

You can feel free to switch between any mix you want that is made with hyperfiltered air, up to the regulator's O2 limit.

EAN36 is hyperfiltered air with an extra 15% O2 added.

EAN22 is hyperfiltered air with an extra 1% O2 added.

EAN21 is hyperfiltered air with no extra O2 added.

Any mix between 21% and the upper limit of your reg will not change the O2 clean state of your regulator, as long as it's made with hyperfiltered air.

What they're saying is that you can't use plain air (Grade D or E) or any Nitrox that's made with plain air if you want to maintain the reg in O2 clean condition.

Terry

 

[Charlie99]

I appreciate all of the posts about this topic. I do have an Atomic SS1 that says that you shouldnt switch back and forth from air to nitrox and back.

The SS1, as a combined inflator and 2nd stage, will never see more than about 140psi. There is absolutely no safety issue of swapping back and forth. That warning is about as ridiculous as the manufacturer that has a warning that says you should use both air and nitrox in their BCD.

My Atomics B1 has the same "don't swap back and forth" warning. The very similar but newer B2 does not, nor does the Z1/Z2. It appears that Atomics initially had a blanket CYA warning, but with more recent equipment has made them more realistic. Maybe they did this so that people would believe their warning on the T2.

==========

As with many subjects, there has been a thread about this.
http://www.scubaboard.com/forums/regulators/189674-has-anyone-used-both-atomic-b2-t2.html

In it I contrasted the two versions of nitrox compatibility of the current generation Atomics regs:

NITROX (EAN) USE — T2 ONLY
At time of purchase, you must decide if this regulator is to be used with EAN
or standard compressed air. If you desire to use EAN, this product must be
dedicated for EAN only and identified as such. Do not switch between EAN and
standard compressed air, as compressed air may contain traces of hydrocarbons
which could contaminate your regulator system with potentially flammable
residues incompatible with EAN. If you use or test this regulator with compressed
air, it must be re-cleaned before EAN use.

B2, Z1/Z2
These regulators may be used interchangeably with air or EAN mixes of up to
40% oxygen concentration at 3500 psi maximum. They need not be dedicated
for EAN use, provided that they are used with air or EAN mixtures that meet
minimum dive industry purity standards.

 

[joey46987]

I really appreciate everyones help and the amount of feedback from this thread. If only the hurricanes can stop messing up my diving down here in key west i could take that nitrox and AOW course!

 

[charlesml3]

Physics.

The tank valve gets colder, whereas the the first stage gets warmer.

I'll accept that. The question I have is :

Is the transfer of gas to pressurize the hoses enough to raise the temperature of any part of the first stage high enough to cause a flash fire?

-Charles