Recirculation Pump DIY Questions

[bmbmkr]

I have a couple questions about recirculation pumps. I see them on the 8" machines, thinkin about puttin one in on my 4x40 upgrade.

A little background on my RO experience. I bought a used Deer Run single post 4x40 for the 2018 season. The next year, I replaced the gas driven piston pump with 1 1/2 Hp electric motor, and a Procon 330 pump, added a 1 Hp low pressure feed pump, a second 4x40, and plumbed in a recirculation loop. It's worked great for the last three years. For the upcoming season, I just bought a new 3 Hp motor and a Procon 660 and am adding 2 more 4x40s for a total of 4. I plan to feed two sets of two 4x40's parallel. I thought I could use the old 330 for a recirculation pump. I'm just not sure how to plumb it in, or IF it will even work, or be worth the effort. I've read EVERY RO post in this forum several times, and there's not been much on recirculation pumps, other than replacing them on factory machines.

For recirculation without a pump, I understand the recirculation needle valve reduces pressure from the concentrate circuit, and allows you to feed it back into the low pressure feed circuit and into the high pressure pump intake. I'm still trying to wrap my mind around how this increases flow though the membranes, thus reducing fouling, but it's been working as long as I don't get too greedy and crank her down too far...and my brain is only SO capable.

My questions are:

A: How to plumb the 330 pump in the in the recirc loop?
Intake after the recirc valve, output tee'd into the LP line feeding the HP Pump? Just the same as the recirc loop without a pump? Or plumb the recirc output
after the HP pump, before the membranes?
I'll still need to use the recirculation needle valve off the concentrate circuit (after the membrane, before the concentrate flow meter) to feed the recirc pump.
And add a switch to turn on the pump when I open the recirc needle valve. And possibly upgrade the recirculation tubing from 1/2" to 3/4" for better flow.

B: Will the recirculation pump output pressure be less or equal to the output of the low pressure feed pump? ( Max 70psi @ 0 flow) I haven't used a LP Gauge
yet, but definitely plumbing one in this year.
I don't want to starve the Recirc pump, and don't want to put more than 14 gpm through the 4x40 membranes (Dow XLE). I don't want to over power the LP
pump with pressure from the Recirc pump, nor starve the HP pump. Do I need a check valve after the recirc pump? Should I put the recirculation needle
valve after the Recirculation pump?


C: I was almost done then had another idea- Should I run both procon pumps parallel, puttin all 990 GPH to the membranes, and keep the recirculation loop
plumbed the way it was- my vessels are only rated to 300 PSI and 275 PSI is the MAX I run at.

FLOW CALCULATIONS

LP FEED PUMP 18 gpm Procon Vane pumps are positive displacement, the low pressure feed pump helps increase pressure after the Procon, but not volume,
so the LP flow won't be added to the total flow through the membranes.

HP PUMP PROCON 660 11 gpm (660/60 min)
RC PUMP PROCON 330 5.5 gpm (330/60 min)
Total Flow = 16.5 GPM split between two sets of membranes = 8.25 GPM which is well under the 13 GPM max for XLE membranes and a 50%
increase from the 5.4 GPM of the 660 alone.

Sittin here typing all of this out in a halfway organized manner makes me think the Recirc out put from the PC 330 pump should come into the HP line AFTER
the PC 660 to increase the flow to the membrane since the HP pump can't pump more flow, just more pressure. Thoughts on this?



Now I just have to run up to the shack and double check I will have enough amps to run three pumps on the RO, and a 2 HP blower running the AOF/AUF for the evaporator and a couple LED lights and the radio.

Had I not got a GREAT deal on a couple more 4" vessels and the 3 HP motor, I could have just went with an 8" vessel & membrane. In a few years I'll be doubling taps, buying a 3x10 and more than likely sell this RO and start on an 2x 8" machine.

Edco distributing is the best place I have found for Procon pumps, I ordered a 330 when I did the initial upgrade ($132 plus shipping). On the first boil of that season, I imploded a 2 1/2x10 filter and the pump ate it- bought another one, they rushed it to me for no extra $$. Just ordered the 660 last week and it's being manufactured as we speak, they said it's come straight from the factory in Arizona. 2 week lead time. I'm glad that A: I'm halfway early on this years upgrades, and B: it's MADE IN THE USA!! After that episode, I also upgraded the filter to 4 1/2"x20".

I have spent the better part of 2 years planning this upgrade, I've been very happy with the increase in taps, decrease in boiling time and wood consumption the RO has enabled. I usually take my 1.5% sap to about 6% with two passes and recirculate the second pass to match the evaporator boiling rate. I'm hoping with the recirculation pump, I can get to 9 or 10% and still not be too hard on the membranes. My 2x6 with hard wood, AOF/AUF runs off about 37 GPH. I built a steam hood last year, if i get this RO done in time I may finally get the pre heater done and get her up to 40 GPH.

If you are still reading, thank you and I'd appreciate any feed back. This forum has been especially helpful over the last 8 years, I'm the only sugar maker in my county with a "real" evaporator, not many sugar houses to go see around here besides a few Amish still boilin over tin pans, collecting in buckets. I'm doin this 99% by myself on a shoestring budget. I retired from the USAF in 2013, & have been farming & sugaring full time since 2016.

Thanks for your time & consideration,

Ben

[darkmachine]

I have been considering building an RO for a while and from my understanding the recirculation pump that prevents the membranes from fouling circulates the sap over the membrane but doesn't go back into the low pressure feed. In other words it circulates sap that is already under pressure in a loop from one end of the membrane to the other. That's my understanding.

[bmbmkr]

4 POST RECIRC DIAGRAM 16AUG21.jpg

Here's a diagram I came up with by answering some of my own questions, by askin y'all yesterday.

Can anyone who has experience with RO with a recirculating pump confirm or deny this flow plan will work? Or if there's a better, more efficient way, please let me know.

Any feed back is appreciated.

Thanks!!
Ben

[bmbmkr]

I have been considering building an RO for a while and from my understanding the recirculation pump that prevents the membranes from fouling circulates the sap over the membrane but doesn't go back into the low pressure feed. In other words it circulates sap that is already under pressure in a loop from one end of the membrane to the other. That's my understanding.

Thanks for your input Dark Machine,

With 500 taps you definitely need an RO if you are runnin a 2x6 evaporator. I had to dump sap my first year with 125 taps and my 20 gph 18"x6' franken-rig, I was gettin over 250 gallon a day. My first few boils I was only gettin 12-15 gph, and had a few 15 hour plus, all night boils. After workin in the woods all day that was not fun. Down here in southern OH, the weather isn't friendly at the end of the season, late February/ early March.

I bought a 2 year old 2x6 raised flue 2 years ago, and double the RO output. I put ceramic blanket behind the brick, brought the insulation right up within 1/2" under the flues, covered the bottom under the grates and added AUF/AOF. I don't have an air tight front yet, but even with 650 cfm, she makes more steam with the ash door cracked open. I'm goin to double the size of the blower this year and see how that works. The original owner was gettin 25 gph out of it, I've had it up to near 40. I've had a few days when I processed 2 days worth of sap- over 1500 gallon. One thing I learned, is that you really have to clean the pans in between every boil. I sure wasted a lot of time makin crappy syrup when I got lazy & tried to get two boils in between cleanin.

[Greg MacWilliam]

You need to be careful when running the 660gph pump with 4 inch membranes, most caps are sized for 1/2 inch pipe which is too restrictive and you will get pressure build up in the lines which is made worse by high pressure recirculating. There are canisters with caps that have 3/4 inch feeds these will work fine. The 660s have 1 inch outlets for a reason.

[bmbmkr]

Thanks for your reply. I do have 3/4" feed ports for all 4 vessels. The first two vessels I got came with 1/2" feed ports, and I swapped them out for 3/4 caps last year. the new vessels I got have 3/4" ports on both ends. It made a noticeable difference even with the 330 pump. I'm still working on sourcing plumbing from the pump to the caps to reduce flow constrictions as much as possible. Even 3/4" NPT-Hose barb fittings are smaller than 3/4" I.D. I'm contemplating using sanitary fittings. 1" tube size. Even then, the tri-clamp to 3/4" npt are a little less than 3/4" I.D. I got the 660 pump this past week, it is HUGE.

I'm still working on how to plumb in the recirculation. I've read through most of the RO posts in the forum all the way back to 2009 and there are a few threads about recirculation pumps. My main concern now is will the 330 fed from the concentrate output through a needle valve get enough feed not to damage the pump itself, and still make enough pressure to feed into the 660 output. There's this thing called delta loss. My latest design is to have two valves, one tee'd off the concentration output, before the needle valve to feed the 330, and another after the 330. The best i can tell, 250 psi from the 660 output will not agree with open plumbing to the 330 out put without a valve that will be opened immediately after starting the recirc pump. I contemplated a check valve here, but wasn't sure how I'd regulate the out put pressure of the 330 to overcome the pressure from the 660. I may be barking up the wrong tree, with this whole idea. I may just end up using the 330 to build another machine and sell it.4 POST RECIRC DIAGRAM 18AUG21.jpg

[bmbmkr]

I had a hard time finding a single phase, 1725 rpm, 3 hp motor with a C-face. Plenty of 2HP out there. The 660 pump curve shows 250 psi and 650 gph @ 2.35 hp. I held out for this motor. 3hp, 15 amps, 1740 rpm from E-bay. I got the Nema adapter and lovejoy connector from Mcmaster-Carr. Ordered Wed night and delivered Thursday morning. They must have a warehouse across the street from the UPS hub.

Procon 660 3 hp 2021.jpg

[Greg MacWilliam]

I run 2 660s on Harbor freight 2hp 1800 rpm motors and they have run great 4 years now. The high pressure recirculating loop cuts in before the needle valve and re enters just after the primary pressure pump, I put a check valve and a ball valve on this loop in case I don’t run the recirculating pump, you may want to consider an 8 inch membrane, switched 2 years ago, easy plumbing, cleaning, and better performance. Got mine from MES, check out falcon stainless for you high pressure lines they work well on the procons but would not recommend for 400psi application.

[bmbmkr]

Thanks very much for the info Greg.


I'm slowly working my way towards 8". Started with a single 4". By the time I get to using 8" I'll have enough parts to sell off two 4" complete RO machines.