O2 cleaning, why and when??

[AquaPixie]

For reason should you have your tanks O2 cleaned and how often?

Once you'v had a tank O2 cleaned must it always be done?

 

[mike_s]

for use with partial pressure filling where pure o2 is introduced to the tank.


how often does it need to be cleaned?
1.) initially the first time before you use it for any mix with over 40% o2, including partial pressure filling.
2.) after any hydro test. (hydro test water is nasty typically)
3.) re-cleaned as required after use/time. (opinions on this will vary).
4.) anytime that it's filled with a "non clean" air source, re-cleaning is suggested.


note: Never trust a tank from the factory to be o2 clean, even if the manufacturer says it is. I've gotten brand new tanks that came saying they were o2 clean but where FILTHY inside.

I'm sure others will have some other suggestions (and arguments).

 

[masterof0]

The key reasons for O2 cleaning are when the tanks will be used for percentages of O2 greater than 40% or when partial pressure blending (exposure of hte tank to 100% O2). If Nitrox is banked and under 40%, O2 clean tanks are not required.

As for how often, most divers O2 clean them during hydro or after exposure to "dirty" air.

 

[soamelt]

When they fill using partial pressure, why can't they put 21% in first and then the pure O2 so the tank is never exposed to pure O2? I imagine it's got to be some sort of explosion risk that way, but don't know why. Either way the 21% is going to come in direct contact with the 100%.

 

[masterof0]

When they fill using partial pressure, why can't they put 21% in first and then the pure O2 so the tank is never exposed to pure O2? I imagine it's got to be some sort of explosion risk that way, but don't know why. Either way the 21% is going to come in direct contact with the 100%.

Becuase even if you "top" with O2, you are still exposing the system (tanks, lines, valves, etc) with 100% O2 which presents a fire hazard. In actuality, you are more concerned with the transport (lines, valves, seals, etc) than the actual tank itself since that is where most of the friction that will generate heat is going to occur. Compression of the O2 will also generate some heat, but the risk is reduced as it mixes with other existing components in the tank.

 

[rstofer]

When they fill using partial pressure, why can't they put 21% in first and then the pure O2 so the tank is never exposed to pure O2? I imagine it's got to be some sort of explosion risk that way, but don't know why. Either way the 21% is going to come in direct contact with the 100%.

Some places don't pump the O2 to a high pressure. Whatever pressure is left in the cylinder is what they have So, if they need to put 400 psi in a tank for a mix, they can take it directly from their tank. Worst case, they have their O2 tanks refilled when they can no longer make a minimum mix. There are a number of staging strategies for this.

What they don't want to do is put 400 psi on top of 3000 psi because once their O2 tank got down to 3400 psi, it would be 'empty'' no longer having enough pressure to make a mix. Kind of a waste.

The numbers are all bogus. I haven't worked out how many psi of pure O2 would be required to make a tank of 32%.

Richard

 

[muddiver]

The reason to have a cylinder oxygen cleaned is if you are going to use for Nitrox. Most SCUBA shops that provide air fills for SCUBA diving use a system that will clean compressed air to CGA Grade E standards. That standard allows a small amount of oil in the air, along with carbon monoxide, water and some other stuff. The oil can build up in the cylinder over time and many fills. Then when you introduce oxygen at an increased pressure you can create an explosion hazard.

Therefore you need to have the cylinder, cylinder valve, first stage regulator, high pressure hoses and pressure gague cleaned for oxygen use. When ever you use the cylinder you should also be careful not to contaminate the cylinder valve and O-ring between dives. Same with the first stage valve connection.