Tanks and Nitrox

[tombiowami]

Ok, I have 2 alum80s I bought a while back and wanted to use nitrox. Got the class, etc. The store I got them from charged 40$ per tank to 02 clean them and said it was mandatory for Nitrox fills as their method is to put pure oxygen in and then fill with air to the correct per cent.

I go on my trip and have fun.

Come back and call scuba shop number two, they do not require 02 cleaning at all because they do not use pure oxygen, but pre mix which does not introduce pure oxygen.

Did I just get ripped off? Or what is the big deal with 02 cleaning?

Tommy

 

[Uncle Pug]

No.

If I were PP blending I would want the tanks to be clean too...

Shoot if I were breathing out of them I would want them to be clean!!!

You can clean your own tanks and valves if you know what you are doing..... but how does the guy putting O2 into them know that 1) you did it? 2) you did it right?

Sure there may not be an explosion but there could be undetected patial combustion with left over CO for you to breath while diving.

If I were having my tanks filled by PP blending I would want them clean....

BTW a shop that PP blends will also (hopefully) have O2 compatible air.... in other words hyperfiltered clean air....

Now the shop that uses pre-blended might PP blend in their own *clean* tanks so they don't have to worry about your tank not being clean enough. In this case their air is probably hyperfiltered too.

A shop that continuous blends may or may not have hyperfiltered air and this may not a be a problem at all. And they can just pump it into your tank and send you down the road happy...

So no you didn't get ripped off because you took your tanks to a shop that PP blends.... and they gotta clean them.... and they deserve to make a living too....

That said.... my tanks & valves are not just clean.... the are O2 cleaned and compatible.... but I continous blend into them so they could be dirty and it wouldn't matter... but I like clean....

 

[Rick Murchison]

Because you have taken your tanks to be filled at a shop that premixes, you *may* have lost your oxygen service rating on your tanks. It depends on the quality of the premix, but if they're using continuous blending upstream of the compressor or they're using a membrane (DNAx) there's a good probability they're *not* sticking to oxygen compatible air standards and you may require another tank cleaning before you can fill by the partial-pressure method again.
If your partial pressure blending shop insists on another cleaning before they'll fill again, don't get upset, just learn from it.
Pure oxygen is not to be trifled with.
Rick

 

[tombiowami]

Thanks as usual for the insight. Is PP blending going away? Why would I go back to the PP and pay for another o2 cleaning when I can just get the premix at the same price? Is there anything inherently better with PP? I understand the flammable nature of o2, and would want clean tanks if I was filling them that way also. The course I had was not specific on some of the real world actions and left me a little confused. Of 3 shops in my area:
One wants o2 cleaning at 40/tank
One says no o2 cleaning needed, but dedicated nitrox tank needed
One says it does not matter at all, bring any tank, just have the nitrox card ready.

hmmmm...

I think the last shop, which I asked more about uses 40% or less premix so does not run into the 100% o2 issues.

A side issue here was the tanks I got came with 10 free air fills apiece which of course I cannot use from that shop and then have them do the nitrox fills. Though to complicate things more, they said they may be going to premix later this year.

Tommy

 

[TexasMike]

I'm not sure if I've seen the answer to this yet, so I'll ask it here...

When you have a tank O2 cleaned, is it marked somehow? Perhaps a sticker like VIP?

 

[Rick Murchison]

Originally posted by TexasMike
I'm not sure if I've seen the answer to this yet, so I'll ask it here...

When you have a tank O2 cleaned, is it marked somehow? Perhaps a sticker like VIP?

Yes, it is marked. It will also say that it is to be filled with only oxygen or oxygen compatible air.
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More and more shops are getting away from partial pressure blending for normal (40% oxygen and less) Nitrox mixes, as it is easier, less expensive in the long run, and much safer. If the shop uses a membrane system (removing nitrogen from the air rather than adding oxygen) then they never have to mess with pure oxygen at all.
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PP blending will never [not for the foreseeable future] go away entirely, as special deco mixes will still require it.
Rick