New LP Steel Tank Question

[CompuDude]

My understanding is that the membrane system is a LP output, so the output from the membrane is subjected to the same filtration in the compressor that any other air would. Am I off track here?

Yes. Most compressors do not output o2 clean air. "Any other air" gets filtered to Grade-E levels for regular scuba use. To be compatible with o2 clean tanks, it needs to be further filtered to Mod Grade-E levels.

Half the reason shops go to Membrane systems (which cost a lot more than partial pressure blending setups) is to avoid the need for o2 clean tanks, since nothing comes out over 40%. The membrane merely takes regular air and filters out some of the nitrogen, so the resulting gas has a higher percentage of 02.

 

[battles2a5]

I did not know that. I stand corrected. Thanks for the info.

 

[deepstops]

I can't speak for all the shops but here in FL, most shops pumping membrane gas are hyperfiltering it to Grade E(2) specs like this place does:
Fill Express -- Premix and Custom-Blend Gas Fills of Air, Nitrox, and Trimix
http://www.fillexpress.com/library/testresults.pdf (August 2007 gas testing results)

 

[Rainer]

If you won't be getting PP nitrox, the cleaning (as others have said) makes no sense. When I buy new cylinders, I get hydros from that very month. Not exactly a new cylinder otherwise. Just not a used cylinder.