Crane 2 Post RO

[darkmachine]

Passive recirculation or poor,s man recirculation as sometimes described on the post , is plumbing a recirculation loop outside of the pressure loop ( tee,s out after the valve and tee's in before the pump) i understand it offers the advantages of a standard brix coming out at a given flow. And reduces fouling : what is recirculated is already filtered , and the flow of the recirculation is not restricted by the filter. It also contibute to a more uniform sugar gradient along the membrane.
Recirculation like the memprotec are plumbed inside the pressure loop ( tee,s out before the valve, and tee,s in after the pump) As i understand it the high volume pump is different than a positive displacement pump (procon) . The objective of this high volume pump is not to provide pressure , since it is plumbed inside the loop already pressurized by the procon, but indeed to provide higher velocity which translate in high flow and increase "laminar flow" that greatly reduces fouling.

So i guess the question is, is it worth it to plumb in the extra procon I have that only makes 125gph. "worth it" as in keeping the membranes cleaner, or should i not worry about it unless i have a pump with a higher flow rate.

[darkmachine]

I'm not sure if you are finally using a procon 330.
With 2 4X40 in series , you will push 330 through the first one , about 40 gph will permeate ,
290 will be pushed through the second one , another 40gph will permeate, so 250 gph should exit the second one .
If you "bleed" 30 gph of concentrate , that gives you 220 gph for the recirculation loop , and a system that process 110gph of fresh 2%sap ( you will not be throwing out sap !!! )
A 125 gph pump within the recirculation loop might actually exert a restriction on the possible flow of 220gph.
A needle valve is required on the recirculation loop, and will be use as the restriction valve that puts the final operating pressure on the membrane.

Save woods for the coming cold spell
and have a great season

I went back and re-read the thread, and somehow i missed the part where my question about using the 125gph pump for recirc might be a bottle neck, lol. That's what I get for skimming. Thanks Sweet Spot Maple. Looks like a second needle valve is in my future. Down the road when i upgrade to an 8" membrane maybe i'll go with a shallow well pump for re-circulation.

[bmbmkr]

I went back and re-read the thread, and somehow i missed the part where my question about using the 125gph pump for recirc might be a bottle neck, lol. That's what I get for skimming. Thanks Sweet Spot Maple. Looks like a second needle valve is in my future. Down the road when i upgrade to an 8" membrane maybe i'll go with a shallow well pump for re-circulation.

Recirculation, with or without a pump, increases concentration. Recirculation with a second pump increases flow and concentration.

Procons are positive displacement pumps, as long as your HP for your recirculation pump motor meets the pump curve and can build the same pressure as your pressure pump, it will increase flow, thus reducing fouling. 330gph (5.5 gpm) + 125 (2gpm) = 7.5 gpm or 33% more flow.

What Sweet Spot brought to my attention- the recirculation feed teeing off the concentrate output of the membrane before the main pressure concentration valve. In the schematic I drew up, and the RO I have 90% complete, I put a second needle valve after the main concentration valve to feed the recirc pump so that I could choose whether to recirculate or not. The only reason I used a needle valve instead of a ball or gate valve, was because i already had it. I HAVE been pondering whether enough the small port would allow enough flow to feed my pump. This is what I love about this firum, so easy to learn if you take the time to read. SO my second control valve is coming off and a tee goin on.

On to the check valve.

The reason I put a check valve in between the recirculation out put and pressure pump feed is so the pressure pump doesn't push the initial feed into the recirc pump backwards. I kinda figured this one out on my own, and another member commented on one of my previous threads confirmed that this is how he plumbed his system. He was using the same size pressure pump as recirculation pump- that's something for me to wrap my head around another time.

I've just revised my drawing, and I have an excel spreadsheet you can punch in your RO and evaporator/tap#'s I can email it- if you want a copy let me know bmbmkr@yahoo.com

Y'all have a good one,

Ben Walker

[sweet spot maple addict]

I am in a continuous learning process, and as i see it , it is gone take me life to learn living !!!

A positive displacement pump is designed to build pressure. It does that by physically trapping a volume of liquid and forcing it to move forward ( within the vanes in the case of procon). If you put a restriction on the outcoming flow, a proportionally pressure results. A procon 330 as example has an internal capacity/dimension to move a volume of 330gph forward and a 125 has the internal dimension to move 125 gph. As i understand if you plumb a 125 in front of a 330, you will not get 455 , where would that liquid be coming from ? And a volume of 330 gph cannot be physically push through a 125 without a restriction .