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Last fall, we had a great discussion on this forum about whether or not we 
need to clean hardware and replace soft goods (o-rings and grease) to make 
it O2 service.

I am just coming back from Florida where I completed my training as Full 
Cave diver.  I had the opportunity to dive on Nitrox and decompress on O2 
and some friends took a Nitrox Diver course.  What I've seen is that what is 
taught in a class often differ greatly from what is done.  I saw people 
putting pure O2 in non cleaned tanks and topping air over O2 with various 
compressors (which didn't look like O2 compatible compressors).

When I came back from there, I took some time to visit a few places around 
here.  I asked an o-ring distributor for Viton o-rings.  He asked me why and 
at what temperature they will be used (after all, it might be too expensive 
for nothing he said).  I said that I need O2 compatible o-rings to use at 
ambiant temperature and high pressure (3000-3500 psi).  He said that Viton 
is not required if I do not use O2 at high temperature (more than 200F or 
95C).  He suggested me to go with Nitrile or Neoprene (sounds like standard 
stuff).  He also told me that Viton will be bad because of the utilisation 
temperature (we still dive when it is minus 20 and Viton o-rings are not 
good below minus 15).  I was a little bit surprised with his comments.

Then, I visited another place which distribute gas and welding equipment.  I 
asked how they maintain the O2 welding regulator and what type of o-rings 
they put into these.  He guy told be that he puts neoprene o-rings in most 
regulator brands.

If all of this is true, why do training agencies require us to modify the 
tank valves, etc.  Is this for commercial reasons?  I did not ask about the 
lubricants.  Is it required to use a special lubricant or not?

I always thought that it was required to put O2 compatible soft goods in 
valves and regulators but according to what I heard, neoprene would be 
compatible at ambiant temperature...

Can someone clarify this issue?

Michel
MTHERRIEN@sh*.mo*.mm*.sh*.co*

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