Small RO output question

[madmapler]

I'm looking at an ro that has 3-4" membranes. It says its rated for 115 gph but all the ones I see with 3 posts seem to do better than that. Is it possible/probable that another post could have been added? How much should a 3 membrane ro process in an hour? Thanks.

[maple flats]

Mine has 2 membranes 40" long and it does an honest 250 gph when I keep the pressure at 270-275 PSI. If the 3 membrane unit has 40" membranes and it runs at pressure in that range I would think you should get 375 gph with about 40 degree sap. What make and length membranes are they? Some types of membranes may be radically different.

[500592]

Is hat the one at bascoms? It probably doesn't have recirc so it would do like 300 an hour. I inquired about that one they said that is what it says on it so that's what they posted up. I chose to buy a used lappiere from a dealer.

[Thad Blaisdell]

feed pump, and high pressure pump would make a huge difference. At 100 taps or so you can build one that would do your needs for about 1200 or less. Very simple to build.

[madmapler]

Thanks for the replies. Dave, I believe they are 40". I'd be happy to get 250 from it. More would be better. 500592,Yes. It is the one at Bascoms.He said the same thing to me. I'm headed up there today to look at it. I dont know much about ROs or what exactly a recirculator is or how it works.Thad, I am looking at buying it and making upgrades to it to bring up the capacity if necessary. I'm going to have at least 800 taps this year on vacuum. I was really leaning toward building one but just dont have the time this year. I'll try to get more info on it and post it later. Thanks again.

[BreezyHill]

A 4 x 40 membrane is rated at 100 gph, the issue is that the second membrane in line is now working with a more concentrated product so there is less water that can be removed and there is a slight pressure reduction due to friction. It is very possible that the unit was designed to have had two membranes/posts and another was added.
The size of the pump is also very important. Low hp=less gpm.

I have a 2 post 4x40 unit with a 5hp circulation pump and a 2hp supply pump. This unit has a history of making 15% sap. This is achieved by recirculating sap thru the system by valves...no recirc pump. Since it is so over sized on the main pump and the main pump is force fed, this is do able.

Then calculate in the high tech membranes available today that run on lower pressures and those old machines are diamonds in a box of marbles; provided you can gt parts and take the time to study the unit and make it work for you.

What kind of unit is it?

[madmapler]

I went up to look at it today and left a deposit on it. Its a small brothers with a 1/2 hp.feed pump and a 3 hp. circ. pump. I could see clearly that it originally had a single membrane and that the other 2 were bolted on later hence the 115 gph. on the tag. They're plumbed in series. I'd like to know if thats the norm or if a parallel configuration is better.I actually have a 5hp. pump that was supposed to be used for something else but priorities is priorities. I'd like to know also what size pump it'll handle. Is the 3hp. sufficient? It does'nt have a recirculator. Can it be modified for one or is it not worth it? I know some guys dont seem to have a problem without one. Thanks.

[wiam]

Does it have a piston pump? My older Memteck with a 3 hp originally had 2 in series. When I went to xle's it would do about 225 gph taking out 3/4 of the water. Last year I added 2 more xle's in series but parralel to the first 2. It will do close 375gph now

[BreezyHill]

You would get more concentration if run in series. I would bet the tag is from the single post and you will want to run it as is. With two posts it will be more than 115.
The xle membranes will help add pump longevity as they take less energy to pass water thru. I bet you have a real gem on your hands. Great Find!
The issue with adding more membranes is you may be stressing the limits of your pump. But there are external posts available with a booster pump that will add capacity if you need.

3 membranes in series should be able to run 250-285 depending on membranes used, sap temp, filter load, pump efficiency, and how you adjust the system. As you get to know the unit you can dial her in and get her to her max capacity.

At 8% you are putting in 4 gallons of 2% sap and getting one out the concentrate line. Remember how many gallons it takes to start your evaporator and how many gallons the evap will eat after your last firing to get it stopped. Now in crease this by 4x as you are working with more sugar less water and you will be drawing off faster...a lot faster.

Always save a bunch of permeate...sometimes you need to flood the flue pan since the finish pan may get low from pulling off and draw the flue down to far. The other option is to empty the flue and flood with perm to clean it when the fire gets low.

I get done really late in night or even early am and just flood the pans and go to bed. Clean in the am with a light fire if needed, out of card board and get cranking when the sap gets going.

I wish I could flood everything with perm and let soak til am and use a pump to spray down and drain of the wash water and get rolling again. I think I have enough stainless milk pails now to do that.

Whats that saying about best laid plans???

[madmapler]

I'm pretty sure its a vane pump. I dont know much about the membranes but this machine sat around for 10+ years so I'm sure they're old. I may replace them anyway. It sounds like I might increase productivity if I run them in parralel. 8% would be fine with me at this point. I would consider putting another post on it if I could get a little more out of it, or as I said earlier, increase the pump size. Are xle membranes the best way to go? I would appreciate all the input and experience you guys are willing to offer. I'd really like to tweak this thing out. Thanks.

[Mark]

I cut the vessels on mine and welded in another 40 inches. I could then put two membranes in each vessel.

[BreezyHill]

The switching to a 8" membrane would be the biggest step up. 8s will last longer before cleaning/flushing is needed and will have a 6x production increase over a 4". Add on an 8" and you double the theoretical capacity of your three 4" system by 2x.

Check out the membranes on page 46 in the link below. There is also other information you can learn in there.
http://www.cdlusa.net/Data/Sites/8/SharedFiles/catalogue-2013-usa.pdf

Happy Reading

Ben

[maple flats]

My 2 membranes are in parallel and at 275 PSI I get between 240-260 gph while removing 3x as much water as I send in concentrate to the tank. My typical flows on the flow meters are slightly over 4.5 gpm permeate and barely over 1.5 gpm concentrate if running about 2% sap at 37-40 degrees in. When I re-concentrate from the concentrate tank and back to the same tank I drop the pressure to about 250-260 PSI and the permeate flow drops as well as the concentrate flow. I don't remember exactly what the flows are then, but they gradually drop until I get to about 14-15% concentrate. My RO doesn't do well concentrating higher than 15%. When I do I end up having to rinse with permeate after 60-90 minutes. I now stop at 14% usually.

[madmapler]

Dave, I've read that you have changed your RO over to electric. Can you tell me what size pump/motor you're using? The one I have a deposit on has a 3hp pressure pump and a 1/2hp feed. I'm trying to figure out if those are optimal for the 3 posts it has. I'm thinking also that I should run from the 1st post into the second 2 instead of the 1st to 2nd to 3rd conf. it presently has. I'm also considering a 4th post and going from 2 to 2 if I have enough pump to do it. Thanks. Also, For you guys who build your own, Where would I pick up a 5hp motor/pump if I were to upgrade. Thanks again!

[madmapler]

I picked up the RO at Bascoms the other day. Since then I've been doing some research. It has a 3hp Tonkaflow multistage pressure pump. From looking at Teuchtars plans(very well done I must say) and reading his posts I gathered that I could increase my pressure by increasing the feed pump size. I was further convinced of this when I got the spec. sheet on the pump and it said that the seals could handle up to 200 psi input pressure. It currently has only 1/2hp feed pump. Has anyone increased their pressure this way? Any reason why it would'nt work? Thanks.

[TunbridgeDave]

I have a smaller version of that SB ro with 2 4x40s. They are the xle, and I get a benchmark of 210gpm at 200psi 55 degrees. That one has a better (Tonkaflow) pump than mine so I would think it would do well. Don't worry about the recirc pump. If you run lower pressures and just recirc the concentrate back to the holding tank you get the most permeate per hour out of the machine and the membranes will not clog as quickly. There is a recirc valve on these machines so you can "one pass" at higher levels if you want. I think these machines are great, very simple and easy to use. If you buy it and have questions, let me know.

[GeneralStark]

With a different machine but similar vintage with a 10hp Tonkaflow, we did achieve higher pressures relative to input pressure. The outlet of the ro feed tank is 12' higher than the HP Pump inlet, so when running with the feed pump on instead of just the head pressure of the tank, the output pressure of the feed pump was higher.

I would have to agree that running at lower pressure and circulating the concentrate back to the raw sap tank to a desired concentration and then passing it through the ro again to achieve your desired final concentration in the evap. head tank is the way to maximize these older machines. We didn't do that and it was tough to maintain a consistent final concentration and the machine definitely fouled faster.