O2 Cleaning

[GLiebmann]

I have a question and please excuse my ignorance. I purchased two fairly new Al80s. I had them visually inspected and asked that they were to be O2 cleaned and filled with NOX32. When I picked them up my shop told me that they didnt need to O2 clean them because they used a Membrane system for filling and at that percentage it was not necessary. They wanted to save me money which I appreciate. If they are filled somewhere else, however, that does not use this type of system its a different story.

My question is after a year of 32% fills, what would be the harm if I had another shop that did not use a Membrane system for filling? Is it really necessary to have them O2 cleaned or at this point would it be okay? I assume that if there would be an issue it would be in the filling process. Of course I dont want to put anybody at risk by neglecting to identify that they were not cleaned. Any advice would be appreciated.

 

[rob.mwpropane]

The other ways to fill would be partial pressure blending or through a nitrox stick.

The stick doesn't matter but the pp blending does for O2 cleaning. They'll dump O2 in 1st and then top off with air. This means the tank would see 100% O2 before the air was added. Stick with a shop that uses a membrane or a stick and avoid the O2 clean (and save the $$).

The only reason to get a tank O2 cleaned is if the LDS is living in the stone age and doing PP blending or you're using it as a deco tank and using a mix of 50% or more. Does that answer your ?

 

[attack33]

If you didn't buy them new, then the folks before you that owned the tank could have done a number of things that would increase the likelihood of a potential issue. For example, using non-o2 compatible grease for threads and o-rings. You could have o-rings in there that are not ideal for o2. They could have had a dirty fill from a questionable compressor that put some hydrocarbons in your tanks.

You could do nothing and never encounter a problem though. However, if it is even on your mind, just have the tanks o2 cleaned and the valves.

I would say more shops partial pressure blend than continuous blend that I have seen. I do both at home and understand why partial pressure blending is more popular with shops: cost.

You'll get a wide range of responses on this question I am sure. Everything from "OMG, you're going to die! Pressure wash your life in Extreme Simple Green!" to "o2 clean is a myth". I find myself somewhere in the middle.

Ultimately, it will be the dive shops policies that are filling the tanks and what level of risk they are willing to take. Most partial pressure blending shops require 'o2 clean'. In the past, I have been rejected for a fill over this. Better to ask beforehand.

 

[GLiebmann]

The other ways to fill would be partial pressure blending or through a nitrox stick.

The stick doesn't matter but the pp blending does for O2 cleaning. They'll dump O2 in 1st and then top off with air. This means the tank would see 100% O2 before the air was added. Stick with a shop that uses a membrane or a stick and avoid the O2 clean (and save the $$).

The only reason to get a tank O2 cleaned is if the LDS is living in the stone age and doing PP blending or you're using it as a deco tank and using a mix of 50% or more. Does that answer your ?

Yes it does, thanks!!

 

[GLiebmann]

If you didn't buy them new, then the folks before you that owned the tank could have done a number of things that would increase the likelihood of a potential issue. For example, using non-o2 compatible grease for threads and o-rings. You could have o-rings in there that are not ideal for o2. They could have had a dirty fill from a questionable compressor that put some hydrocarbons in your tanks.

You could do nothing and never encounter a problem though. However, if it is even on your mind, just have the tanks o2 cleaned and the valves.

I would say more shops partial pressure blend than continuous blend that I have seen. I do both at home and understand why partial pressure blending is more popular with shops: cost.

You'll get a wide range of responses on this question I am sure. Everything from "OMG, you're going to die! Pressure wash your life in Extreme Simple Green!" to "o2 clean is a myth". I find myself somewhere in the middle.

Ultimately, it will be the dive shops policies that are filling the tanks and what level of risk they are willing to take. Most partial pressure blending shops require 'o2 clean'. In the past, I have been rejected for a fill over this. Better to ask beforehand.

Thanks for the response, this was helpful. I forgot to mention I replaced the yoke valves with DIN O2 compatible valves when they did the VIP

 

[Jim Lapenta]

Many shops still do PP blending. Especially for custom blends and in the NE this is common. 32% is not a great mix for say Lake Erie. Too limiting on depth. 28% is a better choice.
Some shops will also PP blend but do it in their own banks and fill customer tanks from the bank. O2 cleaning not needed.
But, if there is a chance that you are going to get a fill at a place that does PP, just get the tanks cleaned.
Oh, and those O2 compatible DIN valves? No longer O2 clean since you've put them on tanks that were not O2 clean. Expect a proper shop to want to clean them again. I would. Even though the seats in most valves are not O2 compatible. The mfg of them won't make that claim out of fear of liability.
And a shop is not living in the stoneage if they don't have a membrane or even a stick. They may be doing a lot of custom blends or don't want to push air greater than 21% through their compressor.
I like PP blending because I don't have to worry about something going wrong with the stick and membrane systems are not cheap.
The shop where I do my fills has a Haskel and it's a nice way to kill some time getting the mix that I want.

 

[Divin'Papaw]

@GLiebmann Something to keep in mind that I've not seen mentioned yet. Some shops that don't use partial pressure blending still require O2 clean tanks. There aren't many, but there a few.

I'll give you a real-world example. Most of the shops down here in South Florida bank their nitrox using a mixing stick setup. The only part of the system seeing 100% O2 is the mixing stick itself and the hoses feeding it from the oxygen dewar/tanks. Most of them do not require O2 clean tanks for their 28/32/36% fills. However, there is one shop that does require O2 clean tanks ... Jupiter Dive Center. Great shop, great staff, very well run and professional, they also run two very popular dive boats. They absolutely will NOT fill pre-blended nitrox in any tank that is not O2 clean. Their shop, their rules. I dive with them all the time and just get my nitrox fills elsewhere. There are plenty of shops in the area that do not interpret the "rules" as conservatively as they do.

 

[GLiebmann]

Very helpful and interesting information.

Thanks Everyone

 

[nadwidny]

Thanks for the response, this was helpful. I forgot to mention I replaced the yoke valves with DIN O2 compatible valves when they did the VIP

Did you clean the threads on the tank first? For all you know the previous owner could have been using vaseline on them.

 

[rob.mwpropane]

And a shop is not living in the stoneage if they don't have a membrane or even a stick. They may be doing a lot of custom blends or don't want to push air greater than 21% through their compressor.
I like PP blending because I don't have to worry about something going wrong with the stick and membrane systems are not cheap.
The shop where I do my fills has a Haskel and it's a nice way to kill some time getting the mix that I want.

I only said membrane because OP did, I've never messed with one. Too rich for my blood.

Could always get a booster (like you said), but either a booster or a stick (or both) would be more efficient in a shop then pp blending.

If someone is going to run a shop have the right tools in the shed. It's 2023, there's no reason to charge a recreational diver for an O2 cleaning. I applaud that the shop talked him out of it instead of just charging him to do it.