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The reason is simple and you kind of answered it already, the shop you’re using does partial pressure blending for any mixture aside from air, and banked EAN32. Partial pressure blending is when a tank is filled with hyperclean 100% oxygen then topped of with hyperclean air, basically if the tanks weren’t O2 cleaned, during the first step of this process the volitile 02 would react with the oils, and other contaminants, and basically eat your O-rings and tank away possibly to the point of combustion. Why both tanks? Who’s to say you won’t oneday want some other mix that has to be blended in both tanks? In Fla, and most other tourist spots, your tanks never come in contact with 100% O2 so no need to worry there.
Another reason is that it’s the shop’s pump and so it’s their rules about what gets hooked up to the pump.
Bottom line they’re looking out for you and them. Just do it. Just wait till you decide you may want to get into Tech diving and you have multiple regs that have to be O2 cleaned too. $$$$
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Jen-Michael,
I was not clear in my post and there is an update. They only use banked 30%. I originally did the calculations to determine how much EAN32 and Air to get the mix I needed and where the confusion may have started. When I clarified with the shop, I was informed that I would need to have O2 clean tanks for a mix greater than 30%, hence the adding of pure O2. I have since adjusted to the EAN30 the shop banks for my calculations.
Now, would O2 cleaning be required for banked/premix of EAN32 or EAN36 or only in the case of partial pressure blending with pure O2? Or does it predominently default to "my shop, my gas, my rules?"
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Both my tanks are O2 clean and as the member before said is mainly used by partial pressure filling. What you described isn’t though, if thay are using 32% and mixing with air they might contaminate the tanks. If you want to keep them O2 clean might want talk to the shop and see what they recomend. I already had a shop in my area told me I shouldn’t filled O2 cleans with them because of their methods.
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Like the other guy said it’s their stupid rules you have to follow. Inreality, if you are filling from a banked nitrox of 32% or 36%, O2 cleaning is not required. I would recommend your tanks O2 clean if you are planning on pure O2 partial pressure fills.
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I checked out your profile, I never had a problem myself getting the fills I need from cave country. I can even get pure O2 fills without all the merit badges.
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Cave country is very ammicable to deal with. Being around metal workers all the time ~ I just wonder what perceived hazards the non-cave dive community thinks they discovered that National Welders, et al have not found. Besides, the shop was going to charge me $50.00 per tank (X-130’s) just for the O2 clean.
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You need to have O2 clean bottles if you blend in the bottle. So if your shop banks 30% and you want 32% they fill partially with the 30% and top it off with 100% to get the desired result. If you just use the 30% you don’t need to clean the cyl.
Steve
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