Partial pressure mixing doubles

[Marcin2005]

wmspdi
PS. Not that I'm that clever but just finished the Trimix Gas Blender course

WOW Mania, I see you've been busy! Gas blender course. Personally I stick to gas passing :11:

 

[rgbmatt]

If I have more than 1,500 PSI left after my dive I have the tank topped off with hyper pure air, analyze the resulting blend (usually around 28% to 30%) and dive it.

There's nothing at all wrong with this. No point in wasting perfectly good O2! As long as the gas you're putting in is clean, you can put whatever you want into a Nitrox tank.

But, make sure to give the tanks enough time for the gas to settle before you analyze them. Right after filling, the air won't have mixed in properly and you'll get an inaccurate reading.

The point may be moot now. I was surfing the web and I just found an LDS much closer to home (about 45 mins away) that banks NITROX 32%. I called and found they only charge for the gas used at $.19 per cf, and they can fill the tanks while I wait. The LDS I had been using required that I leave the tanks for 2 days and then drive back for pick-up (2.5 hours round trip). Since I don't need a 36% blend, and can live with 32%, I am making the switch and will have them convert my single tanks to doubles. End of problem!

Make sure to check whether or not the 32% from this new place is O2 clean. If it's not, then your tanks will no longer be O2 compatible and you won't be able to (safely) get them filled at your old shop.

On the other hand, though, if you plan on getting your tanks filled only at the new shop, then you can save yourself some cash by not O2 cleaning your Nitrox tanks. O2 cleaning is only required if you're filling your tanks with more than 40% oxygen. You can fill any tank with 32% if it's already mixed.

 

[wmspdi]

If you plan on getting your tanks filled only at the new shop, then you can save yourself some cash by not O2 cleaning your Nitrox tanks. O2 cleaning is only required if you're filling your tanks with more than 40% oxygen. You can fill any tank with 32% if it's already mixed.

That's the plan. The last VIP/O2 cleaning cost me $65.00 per tank/valve. Between higher cost of the gas, the travel time to the custom blender for refills (drop off then pickup at close to 2.5 hours each round trip) and the above mentioned cleaning costs, the pre-banked gas at $0.14 per cubic foot of fill is a real deal.

Regarding analyzing tanks after re-filling... there would always be at least a few hours between the fill and tank use so the gas will have plenty of time to migrate. In addition I always re-analyze the tanks before use to confirm the blend before setting my computer, even if the tank was filled from a NITROX bank.

 

[mania]

WOW Mania, I see you've been busy! Gas blender course. Personally I stick to gas passing :11:

Well, the course was sort of a part of Advanced Nitrox....
And we have a blending station so it's worth knowing how to do it - otherwise I will always have to ask somebody to do it for me.
Mania
PS. But still my favourite way is simply to use the gas rather than blend it

 

[Furner]

Im no expert, but I was just reading through the Luxfer Guide to SCuba Visual Inspection of cylinders, and they several times stress that no tank should ever be filled to any pressure with pure O2. I quote "Never: fill or partially fill a cylinder with pure oxygen".
I am sure they are just concerned about the use of parts that are not O2 clean, but they dont mention anything that I see about that it is ok to partially fill with O2 after a tank being O2 cleaned and proper parts being used.