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>I understand that at least one agency requires all cylinders put into
>enriched
>air service to be cleaned and labeled. Others state that for under 40%
>use, no
>cleaning is necessary, but I believe they are still specially marked and
>labeled.
The general consensus is that if a cylinder will never come in contact
with gas that is "richer" than 40% O2, it does not need to be cleaned.
Note, however, that there are some Nitrox blending methods, known as
partial pressure filling, that will cause a cylinder to come in contact
with 100% O2 even if the final mix will be less than 40%. It is for that
reason that some facilities require O2 cleaning even though the user will
only see less than EAN40 mixes.
>
>My question is when someone brings a cylinder to my store, how can I tell
>whether it has been:
>
>1) labeled but not cleaned for less than 40% use
>2) labeled and cleaned for over 40% use
>3) labeled and cleaned for any mix
>
>Is the labeling different? When a less than 40% cylinder gets filled with
>EAN50
Nope, although I DO have a sticker on my tank, placed there by the
facility that cleaned the tank, that states that it has been O2 cleaned
and serviced. Big deal. One fill from bad fill station and the tank is
no longer O2 clean.
As a Nitrox blender, if I'm using partial pressure filling methods, I
will NOT fill a tank unless I know that the tank is clean to O2. How do
I know this? Several ways...
1) I know the diver personally well enough to take his word for it.
2) The tank was filled at our facility and there's still gas of the
correct percentage in the cylinder (I analyze BEFORE putting any gas into
the tank and compare it against our logs)
3) The tank has gas in it that is greater than 40% O2 content.
>or EAN80, does it get a different label or marking?
Nope.
>
>What if someone buys a cylinder, properly labeled for EAN, and says he will
>never put more than 36% in it. He goes to some other dive store and asks for
>50%. He's certified for 50%. How does the dive store know the tank is
>clean?
See above. If you don't know that the tank is clean, you can give the
customer a couple of choices.
1) Get gas elsewhere
2) Have your technician re-clean it
3) Refuse to allow the tank to come into contact with anything above 40%
(i.e. tell the customer that you'll fill it to 40%, and only if you're
using a continuous blending system or a de-nitrogenating system).
>I can think of several ways to know its *not* clean.
And I bet none of them are pretty ::grin::
>
>Regardless of your position on cleaning, the general concensus seems to be
>that
>at some point, 23.5, 40, or whatever, cylinders and valves should be cleaned.
>
>Can a fill station determine the cleaning history of a cylinder by its
>labeling
>or is there another way I'm not aware of?
The problem is that once the tank leaves the cleaning station, there's no
guarantees that it REMAINS clean. a fill from, say, a boat compressor
may inject hydrocarbons into the tank. The next time one pumps 100% O2
into the tank there is a reasonable potential for... er... spectacular
occurrences. I do not mean to say that it's guaranteed to happen, just
that the chances have increased.
-- Kevin --
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