Bad memory? O2 Clean required for less than 40% nitrox

[SomeGuy509]

Hi All,

Maybe my memory is failing me but I was under the impression that if you run less than 40% nitrox 02 cleaning is not required. For example my regs are not O2 clean and I happily run 30% all the time. This is what I recall from my training. The justification being is that the mix is not oxygen rich enough to cause problems yet.

So what I am trying to figure out is why every shop I am calling to VIP my PST 120s is saying that I need to get my tanks 02 clean. Is this simply due to the heating that occurs during the fill increasing the risk of a fire? Or are all these shops just blowing smoke?

 

[Marie13]

O2 clean tanks NOT needed if the shops premix and fill your tanks from banked nitrox. If they have to do partial pressure blending in your tanks, then you DO need O2 clean tanks.

 

[Scared Silly]

O2 clean tanks NOT needed if the shops premix and fill your tanks from banked nitrox. If they have to do partial pressure blending in your tanks, then you DO need O2 clean tanks.

Wrong. Cylinders being filled with more than 23.5% O2 are required to be O2 clean. That is what the CGA rules state which are referenced by the US CFRs.

The above myth gets debunked as nauseum.

 

[SomeGuy509]

Wrong. Cylinders being filled with more than 23.5% O2 are required to be O2 clean. That is what the CGA rules state which are referenced by the US CFRs.

The above myth gets debunked as nauseum.

Ah, that explains everything then. Thank you!

 

[Centrals]

How often would the nitrox tank need to be O2 cleaned please?

Thank you.

 

[chillyinCanada]

@nadwidny

 

[Divin'Papaw]

Wrong. Cylinders being filled with more than 23.5% O2 are required to be O2 clean. That is what the CGA rules state which are referenced by the US CFRs.

The above myth gets debunked as nauseum.

However ... NO ONE (except for one shop I am aware of) interprets the "rules" this way and enforce this unnecessary "rule". I've gotten pre-mixed nitrox fills in many locations across the US and there is ONE SHOP I've ever come across that requires O2 clean tanks for pre-blended nitrox.

I've been filling non-O2 clean tanks with pre-blended nitrox for over a decade. I know of countless shops that do the same day in and day out. No boom.

 

[Marie13]

Bingo! The only time I’ve been required to have O2 clean tanks is for partial pressure blending.

For banked fills? Not that I’ve run across.

 

[Scared Silly]

However ... NO ONE (except for one shop I am aware of) interprets the "rules" this way and enforce this unnecessary "rule". I've gotten pre-mixed nitrox fills in many locations across the US and there is ONE SHOP I've ever come across that requires O2 clean tanks for pre-blended nitrox.

I've been filling non-O2 clean tanks with pre-blended nitrox for over a decade. I know of countless shops that do the same day in and day out. No boom.

Many shops follow the rule, some do not. As such, your emphasis on no one is misplaced. Especially as you even note an exception. And no boom does not mean no problem.

There are some cases I have heard about where there have been issues when filling directly with nitrox sans O2 cleaning. However, finding documentation has been hard.

How often would the nitrox tank need to be O2 cleaned please?

Thank you.

I clean as appropriate. Which is after a requalification or after an annual inspection that shows contamination. The latter, an inspection is done after questionable fills.

 

[rob.mwpropane]

How funny is it when the LDS requires that the sticker is punched out for "Cleaned for mix up to 40%" but then proceeds to PP blend w/100% O2 to get the 28% I'm asking for..... by all rights shouldn't it be O2 cleaned or not?

How does one clean for 40%? You use super diluted simple green?