edwants2dive
Glowstick
Just wondering on this one because of the method used to hydro. Do the facilities use "air" that would maintain the integrity of an o2 clean.
Question Does/Should Hydro negate o2 clean
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Just guessing but I would have to believe the tank would need recleaned - they would have to be sure the water the tank was imersed in was clean and the outside of any tank was clean before testing....
Luis Valenzuela
New
You need to o2 clean after hydro a lot of hydro facilities recycle the water used for hydro and you really don’t know what’s in the water, from what I’ve seen hydro facilities also don’t use breathing air to pressurize the tanks for the hydro
OMyMyOHellYes
Contributor
OP
edwants2dive
Glowstick
Kind of what I thought. I guess the gas supply places that do that say on their O2 tanks clean them after hydro.
Scared Silly
Contributor
The first half of your statement is correct the second half of your statement is incorrect (and contradicts the first half).
Air is NOT used pressurize the tanks for the hydrostatic test. Water is used.
For the OP, a facility that I used tested a lot of medical O2 cylinders. After a hydro test, each cylinder was steam cleaned, dried, and put back into service.
OP
edwants2dive
Glowstick
I knew water was used. I mistakenly thought that the tank was filled with water then a gas was used to get to test pressure. After researching I found that water is use for the whole process.
Now that statement disturbs me. Steam alone will not remove all contaminants that are susceptible to rapid oxidation and pose an autoignition threat. Some form of cleaning agent must be used.
The Chairman
Chairman of the Board
Tanks need to be re-cleaned every five years anyway.
Is any cleaning beyond what is done for a "normal" air tank really necessary for 32%?
Here in the PNW I use air in my pony......but when I haul it to Bonaire I just empty it for transport and then transfill 32 into it once there...
OMyMyOHellYes
Contributor
In practice necessary for safe operation? My speculation? I believe tank and valve manufacturers stand by the 40% limit when saying EANx safe (check to make sure).
But for regulatory purposes? Yep.
Some relevant standards, depending on application:
ASTM - 25%
CGA - 23.5%
NFPA - 21-25%
NASA - 21%
My training (PSI-PCI) included application of CGA G4.1 (thus the 23.5% standard above) as incorporated by reference in Federal regulations (49 CFR) - DOT.
CGA G4.1 Cleaning of Equipment for Oxygen Service includes:
"Scope: This publication describes the cleaning methods and requirements for equipment and used in the production, storage, distribution and use of liquid and gaseous oxygen to reduce the risk of fire, explosion, or promotion of combustion. Cleaning in accordance with this publication is required for all surfaces in contact with a gas or liquid that has an oxygen concentration greater than 23.5%."
So for any tank I'd label "NITROX" I'd oxygen clean it upon return from hydro and maintain it as such.
I don't currently maintain any of my bottles for EANx service (as locally, in shallow lakes, it doesn't make sense), and when I go someplace like Roatan or Bonaire, I try to transfill my pony from straight air tanks or ask for air fill from the filling station.
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