DIY EAN Membrane build

[Ty Hamby]

Considering my next project to be a EAN Membrane LP screw compressor for my 5406 HP compressor. Is there a source for information on a Nitrox membrane build like this?
What size screw compressor for 13cfm HP compressor?
What size refrigeration dryer?
What brand/model/type of membrane?
What inline oil removal filters would be needed?
Any DIY examples I may have missed? Looked here and on YT. Not much info out there.

I have the general idea of how it works but have no clue on the specs of each item of the build.

Like most my projects, I don't do it to save money. I do it to gain the knowledge and convenience.

Any help is appreciated.

 

[rjack321]

Considering my next project to be a EAN Membrane LP screw compressor for my 5406 HP compressor. Is there a source for information on a Nitrox membrane build like this?
What size screw compressor for 13cfm HP compressor?
What size refrigeration dryer?
What brand/model/type of membrane?
What inline oil removal filters would be needed?
Any DIY examples I may have missed? Looked here and on YT. Not much info out there.

I have the general idea of how it works but have no clue on the specs of each item of the build.

Like most my projects, I don't do it to save money. I do it to gain the knowledge and convenience.

Any help is appreciated.

If you run your whole supply gas through, your LP compressor is going to be in the ~35cfm range (aka enormous) to feed a 13cfm HP compressor, although you could have a huge LP bank instead (which will itself be huge)

Alternatively if you only want to produce 1.8-2cfm ~98% O2 to then mix with your normal inlet air and derive 32% you can get away with a much smaller LP compressor and smaller membrane.

The membrane is the same as a "nitrogen production membrane" just keeping the O2 enriched side and discarding the N2. Your gas will be slightly enriched in argon. You'll need to have an in-line air heater to maintain the gas at a stable temperature for consistent O2 output. Oil will instantly destroy the membrane so you absolutely need to only push clean air against it. The feed gas will need to be as clean and dry as scuba air

Total cost is going to be pushing $15+K which is why you don't see any DIY versions. The Nuvair site has some diagrams of all the bites and pieces in their manuals

 

[Ty Hamby]

Total cost is going to be pushing $15+K which is why you don't see any DIY versions. The Nuvair site has some diagrams of all the bites and pieces in their manuals

$15K... Holy sheet! Well that only inspires me more to do it, and ill do it for well south of $15k. I am being slightly arrogant. No not slightly, fully arrogant. This whole air blending hobbie is beginning to suck more and more of my time. I thought scuba was a time suck. Gas blending is really my current time suck. Thank you for your information. The investigative research continues.
Another member here has offered to fill me on the parts/item list from a popular membrane system used in many scuba shops. Ill start there and modify for my desired cfm using surplus parts. I know you are wishing me luck. Thanks.

 

[Wookie]

35 CFM will make you 36% from a 5406 all day. It's what I used on Spree. Will take 15 HP, so a little more than the 5406.

Yes, I can help you design a system. The membrane isn't to make nitrox, it's to make nitrogen. The nitrogen is used to purge wine casks to prevent the wine from fermenting any more.

As long as you understand what you are making, and that the nitrox is actually the waste gas from the membrane, it becomes easier.

Filtration is your friend. I have manuals for the system I built. They are likely in my wife's computer.

 

[Wookie]

PS. A nitrox membrane from a scuba supplier will cost north of $10K

A nitrogen membrane will cost about $2k

They are identical.

 

[Ty Hamby]

PS. A nitrox membrane from a scuba supplier will cost north of $10K

A nitrogen membrane will cost about $2k

They are identical.

$2k, Now we are talking. Id love to see plans with specs. Share if you find time. TIA

 

[grantmac]

Consider harvesting parts from medical oxygen concentrators?

 

[tbone1004]

Consider harvesting parts from medical oxygen concentrators?

O2 concentrators use pressure swing adsorption to separate the gases which is different than permeation used for membrane systems. The PSA systems are not really "continuous" since they have to pressurize each "side" of the device to get the N2 to stick to the zeolites.

Should be noted though that the 5lpm concentrators are good for 1-2cfm of compressor to produce EAN32 so you would need around 10 of them to feed a 13cfm pump and that is very much not cost effective from an electrical bill standpoint.

@Ty Hamby you should probably pay attention to this bit. There is a reason that membrane systems are effectively extinct, they are a REALLY inefficient way to make nitrox. They are horrifically expensive to both built and operate and should only be used as an absolute last resort. For @Wookie it made sense to have one on the boat so it would be self contained and didn't have to get O2 cylinders passed back and forth, for really remote places they make sense when you can't get distilled O2, but I have never actually seen a membrane system in operation in a land-based US dive shop, and it's because they don't make any sense. If you have nearly unlimited cheap electricity, don't care what your power bill is, or really want to do it because it scratches some itch then go for it, just understand that it is not the "right" way to make nitrox. You will save thousands of dollars of both up-front cost as well as save a considerable amount in $/cf by building a stick and just buying bottles of O2, not ignoring the complexity savings.

If you search my posts I am all for doing fun engineering projects, especially to save money vs. commercial available solutions, but this is not a rabbit hole I would recommend you go down.

 

[Wookie]

O2 concentrators use pressure swing adsorption to separate the gases which is different than permeation used for membrane systems. The PSA systems are not really "continuous" since they have to pressurize each "side" of the device to get the N2 to stick to the zeolites.

Should be noted though that the 5lpm concentrators are good for 1-2cfm of compressor to produce EAN32 so you would need around 10 of them to feed a 13cfm pump and that is very much not cost effective from an electrical bill standpoint.

@Ty Hamby you should probably pay attention to this bit. There is a reason that membrane systems are effectively extinct, they are a REALLY inefficient way to make nitrox. They are horrifically expensive to both built and operate and should only be used as an absolute last resort. For @Wookie it made sense to have one on the boat so it would be self contained and didn't have to get O2 cylinders passed back and forth, for really remote places they make sense when you can't get distilled O2, but I have never actually seen a membrane system in operation in a land-based US dive shop, and it's because they don't make any sense. If you have nearly unlimited cheap electricity, don't care what your power bill is, or really want to do it because it scratches some itch then go for it, just understand that it is not the "right" way to make nitrox. You will save thousands of dollars of both up-front cost as well as save a considerable amount in $/cf by building a stick and just buying bottles of O2, not ignoring the complexity savings.

If you search my posts I am all for doing fun engineering projects, especially to save money vs. commercial available solutions, but this is not a rabbit hole I would recommend you go down.

See most of the Keys dive shops, including Capt. Hooks, Quiescience, Blue Grotto, etc. Yes, A CB system is far less expense, but as the OP stated, he's playing around and burning cash. PP blending is a PITA and requires O2 clean cylinders, also a PITA.

 

[tbone1004]

See most of the Keys dive shops, including Capt. Hooks, Quiescience, Blue Grotto, etc. Yes, A CB system is far less expense, but as the OP stated, he's playing around and burning cash. PP blending is a PITA and requires O2 clean cylinders, also a PITA.

probably should have clarified with "mainland" vs. land based, Keys are a bit annoying and expensive to get industrial gas cylinders delivered, but I have legit not seen one in probably 15 years outside of an island or boat installation. PP blending is dumb, agreed.