DIY EAN Membrane build

[grantmac]

Running a stick has other challenges though in terms of compressor maintenance and potential issues if a control fails though from what I can tell. At least from what I can see.

Then again I've only got a little 5cfm pump which I run with no automation so perhaps a stick wouldn't be difficult to manage. 20l/min of O2 should do it if I'm calculating correctly.

 

[Wookie]

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.

A liquid dewar with pressure building regulator would be perfectly satisfactory for almost any large scale operation.

I have a membrane laying around if someone needs it. It’s a UBS, probably sufficient for a Utilis or 5405. Not nearly large enough to meet the OPs needs

 

[rjack321]

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

A nitrogen membrane will cost about $2k

They are identical.

As you know, there's much more than $2k for the membrane

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.

There was a leased membrane system in a local Seattle shop called Starfish back in the 2005-2008 era. They went bankrupt trying to make the payments on their vastly excessive LP pump, LP storage, gas heater, filtration, and membrane. Dive shops are already a fabulous way to lose money, membrane systems just accelerate that decline.

 

[Ty Hamby]

I knew building a membrane system would be expensive. I did not realize running a membrane system would also be so expensive. Here in the Sacramento Valley, I pay approximately $50 per K size cylinder for o2. I have approximately 2700cf of bank. Takes me over 2 cylinders of o2 to fill the bank to EAN32. I foolishly thought that once I had a working membrane system I could fill the bank for less than $150. From what I am reading here you all mostly believe that using the stick is less running cost. I was trying to save hassle and money by going with a membrane. Since I only own 1 K bottle, it's a hassle keeping up with my o2 needs.
2 of the 3 dive shops in my area are using a membrane for nitrox. I figured membrane nitrox was the go to method for LDS's. Sounds like I need to invest in more o2 cylinders to maximize my fill efficiency.
I was looking forward to this project, now...not so much.

 

[rjack321]

Only 1x 250cf? Just get a couple more, they are vastly cheaper than a membrane system.

How deeply are you drawing that bank down? I have 2x 4500, 2x 3600, 3x 2200 bottles for about the same volume as you. The 4500s never get below about 3200, the 3600s I draw down to perhaps 2500, and the 2200s go the lowest to 1500 ish. To top all that off is less than 250cf of O2.

 

[Johnoly]

I did not realize running a membrane system would also be so expensive. SLOW.

I fixed that for you also, cause you won't be in a hurry to fill tanks either.

 

[TravisD]

My most recent Nitrox banking session (my second ever...) I had pulled my 5x3500 bank (which I *think* is roughly 1800cf?) down past usable - the top cylinder was below 1500 psi - it equalized to about 700psi. It look me roughly 1.5 K bottles of O2, running the stick at 39.x % to top it up.

The shop I teach for now has a membrane system, but I haven't really seen it it use or know any of the pros or cons. I get the impression that one big Pro is that it's able to run fairly unattended. My home stick is still kinda evolving, but I don't really see a point where I'd be comfortable walking away from it while in use. Perhaps one of the fancy sticks with a controller would allow for that. I don't even yet have a shutoff solenoid on it, but it's in the works.

Oh, and just as a data point I paid $55 per K bottle for welding grade O2 this time... no corporate account or anything to get into a better pricing tier, but I'm also not going thru very much nitrox, though I am trying to use it more often now that I know what it takes to make it.

 

[rjack321]

Oh, and just as a data point I paid $55 per K bottle for welding grade O2 this time... no corporate account or anything to get into a better pricing tier, but I'm also not going thru very much nitrox, though I am trying to use it more often now that I know what it takes to make it.

My little 125cfs are $38 now I think. I pay way more for 2 of those than a single 250 BUT I got them in my pre booster days and was running a cascade to fill my deco 40s to 2000psi at the time. I own them and it's hard to justify buying a 250 which is a beast to get in and out of the truck & saves me maybe $25 per year in O2 costs which are mostly for CCR nowadays.

Even the cheapest home brew membrane is never going to remotely pencil out cost-wise compared to a 2nd 250cf. I get it it's more the convenience of the membrane, but your time building it is going to vastly exceed your cylinder exchange time too.

 

[tbone1004]

I knew building a membrane system would be expensive. I did not realize running a membrane system would also be so expensive. Here in the Sacramento Valley, I pay approximately $50 per K size cylinder for o2. I have approximately 2700cf of bank. Takes me over 2 cylinders of o2 to fill the bank to EAN32. I foolishly thought that once I had a working membrane system I could fill the bank for less than $150. From what I am reading here you all mostly believe that using the stick is less running cost. I was trying to save hassle and money by going with a membrane. Since I only own 1 K bottle, it's a hassle keeping up with my o2 needs.
2 of the 3 dive shops in my area are using a membrane for nitrox. I figured membrane nitrox was the go to method for LDS's. Sounds like I need to invest in more o2 cylinders to maximize my fill efficiency.
I was looking forward to this project, now...not so much.

If you want a convenient way to do it, get with @Tracy and get an O2 concentrator and compressor to refill the O2 bottles. This is the same way they generator O2 in Truk and some other remote places. Operating cost and simplicity is much easier than a membrane and less of a hassle than going to gas suppliers for K bottles. If you search on here for Invacare you'll see some setups that we have made for using medical oxygen concentrators and then the respective compressors to get ~2000psi O2 banked.

The 5lpm plus compressor uses ~600w and generators about 2lpm, which is about 4cf/hr. Not sure what your power bill is but it is ~$0.05/cf in power cost plus the upfront cost of the pump setup, so direct cost is $13-15/k bottle ish plus say $1k for the setup to do it. ROI is conservatively after40 K bottles, plus the convenience of being able to directly fill scuba cylinders with pure O2 which is super convenient if you're doing a lot of OC decompression. The argon is still in there like it is with a membrane, so be careful if using it for CCR fills, but for OC breathing gases it's perfectly fine.

 

[Tracy]

I knew building a membrane system would be expensive. I did not realize running a membrane system would also be so expensive. Here in the Sacramento Valley, I pay approximately $50 per K size cylinder for o2. I have approximately 2700cf of bank. Takes me over 2 cylinders of o2 to fill the bank to EAN32. I foolishly thought that once I had a working membrane system I could fill the bank for less than $150. From what I am reading here you all mostly believe that using the stick is less running cost. I was trying to save hassle and money by going with a membrane. Since I only own 1 K bottle, it's a hassle keeping up with my o2 needs.
2 of the 3 dive shops in my area are using a membrane for nitrox. I figured membrane nitrox was the go to method for LDS's. Sounds like I need to invest in more o2 cylinders to maximize my fill efficiency.
I was looking forward to this project, now...not so much.

There is also a less standard and much cheaper option. You can fab up a ghettobrane (patent pending) system by feeding prebuilt oxygen concentrators into a nitrox stick feeding your compressor. These are powered by an auxiliary relay circuit triggered on by the compressor contactor.