Is RO without Flow Meters Practical ?

[Wizbi]

I have a RO design in mind that is ~0.2gpm.

Posts by DieselPro identify flow meters for low flow is problemsome. There are not very many options for flow meters for 0.1 to 1.0gpm. Also flow meters for high pressure (~200gpm) are not cost effective.

What are the pitfalls in doing a RO design without using flow meters.

Can one use pressure guages at input to RO membrane and output of RO membrane (prior to needle valve) -AND- manually fill containers with permeate fluid and also concentrate to determine relative flow rates?

Flow meters cost ~100.00ea. Eliminating these from the design saves also in plumbing costs.

[moeh1]

Here is an example of low rate flowmeter you could use economically (not my listing):
http://www.ebay.com/itm/VFA-EC-43-DWYER-FLOWMETER-0-20-GPH-NEW-OLD-STOCK-/291238837549?hash=item43cf2ffd2d

[BreezyHill]

I have a RO design in mind that is ~0.2gpm.


What are the pitfalls in doing a RO design without using flow meters.

An RO without flow meters is like taking a walk thru the bush on a nice sunny day with your welding mask on.

Sounds great bu there is so much you are missing...Is the prefilter clogging or not. It may look dirty but if the flow is sufficient why change it and waste $$$.

Do you need to wash the membranes or are they preforming at a level that is acceptable and is only slightly lower and a good rinsing will have them back to 100%...Savings of hours and electricity and RO soap.

Are the membranes passing sugar due too to much flow across the membrane.

http://www.ebay.com/itm/390295355045?_trksid=p2055119.m1438.l2649&var=660018863784&ssPageName=STRK%3AMEBIDX%3AIT

For what you are looking for a $30 investment will pay back dividends far exceeding expense at the end of the season.

I have had to change filter mid day...without a flow meter I would have not realized that there was an issue.

Upon changing to xle membranes I had a sugar passage issue and the flow meter was how I provided the Dow tech the info needed to determine the flow across the mb was to high.

The other tool I strongly suggest you buy is a refractrometer to read the sap sugar level. If paid for itself on the first rinse of my RO that I used it. It is amazing how much sugar gets lodged in the membranes and it has taken as long as 10 minutes to get the rinse to 0%. Below 1% goes down the drain the rest goes to a batching tank.

Sure you can have a stop watch and graduated tanks and pitchers to monitor flow rates but why spend 3 minutes to accomplish what can be done in the blink of an eye. During sap season I am always looking for ways to do everything better to achieve the best efficiency. I have to have a setup that my wife, sons or their girlfriends can start, run, adjust, and give me on the phone information when something seems not right. IF you are fortunate to have endless hours to process sap and boil syrup then maybe skip the flow meter but I will guarantee you that if you buy it you will not regret it. The meters list work very well and I have a 3-35 to order for my redesign of my RO for next season.

IMO the more tools you have the less time and money that is wasted. Only buy the tools you need and the investment will pay off.


Ben

[bowhunter]

It's possible but not practical. You can foul a membrane in just a few minutes if flows are not in the proper range. Remember the flow meters are located in the low pressure parts of the system so they don't have to withstand 200psi.

[Wizbi]

Does anyone have a good source for Flow Meters in the range of .1 to .5 gpm ?

My RO system will be very small, membrane is rated 225gpd (0.16gpm) at 100psi. I understand this translates to ~(0.31gpm @ 200psi). Am I correct to think that a 0.2 to 2.0 gpm flow meter not have the fidelity to measure 0.1 to 0.3 flows. Seems like only 15% of the readout range would be used. I would think I need more visibility in the 0.05gpm to 0.5gpm range. Dwyer makes a .1-1.0gpm for ~$96.00. Anything else being a better match for 0.3gpm ?

[Wizbi]

Bowhunter,

BreezyHill (Ben) indicates you are the godfather of RO DIY. As such, your advice is golden.

I notice your signature details indicate that your RO does 18gph with a 2.5"x40" (Axeon?) NF4 (-2540?) (rated as 680gpd (i.e. 28.3gph) permeate w/ 15% recovery at 100psi) membrane, Using your 18gph quote and the spec ~140gph Procon pump feed flow rate, I calculate you are operating at a ~13% recovery rate (i.e. 18gph / 140gph).

Question 1: What type of circulating pump do you use to feed the 140gph (2.3gpm) Procon high pressure pump? Any issues with your pump choice?

Question 2: Why did you select the NF4-2540 ? How would the XLE (NF5-2540) membranes compare for maple sap concentrating ?

Question 3: What flow meters do you use to monitor the 140gph (2.3gpm) feed flow and the 18gph (0.3gpm) permeate flow rates? Is the scale sufficient to distinquish changes in permeate flow? I assume that during cleaning/rinsing mode, your permeate flow would be much less (almost nil) since you open the concentrate needle valve to increase concentrate-side flow rate.


I notice you had 71 taps on buckets in 2015. In my area, on a regular sap flow, I get ~1 gallon 2% sap per tap. With this in mind, I would think that if your 71 taps produce 1 gallon sap per day yielding 71 gallons of 2% sap, then your 18gph RO can reduce 71 gallons of 2% sap to 18 gallons at 8% in roughly 3hrs. Do you achieve this - or am I missing some important additional consideration?

[bowhunter]

I'll have to thank Ben for stroking my ego.....anyway if I can help someone have a little more fun while cutting and splitting less wood, I'm happy to do it. You're right on the recovery. I target around 11-12%.

1. I only use 1 pump, the ProCon 140 GPH, to feed the unit and provide the recirculation flow. I like the pump fine...no issues. The pump needs to be sized to the membrane to get the low recoveries and keep the concentrate flows up. I believe in the old adage "the simpler the better." One pump works just fine for these small units. On a larger unit it is more energy efficient and probably less expensive to use a low flow feed pump and a high flow recirculation pump rated for the higher pressure.

2. I chose the NF4 as a compromise between the high performance of the NF3 or Dow NF270's and the XLE's. The XLE's will work but they process less sap than the NF3(Dow NF270) or NF4(Dow NF90). I was concerned about the NF3's potentially passing sugar or some impact on flavor. I think it's been well established that RO does not have any negative impact on syrup flavor so I wouldn't worry about that. The NF3 or NF 270's are very sensitive to pH. You can only use 10% as much sodium hydroxide (lye) or soap to clean them as the NF4, the NF90 or the XLE's.

3. I use the Blue White F-440 Rotameters for net concentrate and permeate flow. 0.025 - 0.25 GPM for net concentrate and 0.1 - 1.0 GPM for permeate flow. The permeate flow is almost zero during cleaning. I like to flush and clean at around 75 psi. My pump seems to run quieter. I always test the membrane at the end a permeate flush to see how close it comes to the "post cleaning" conditions. I run the test at 100 psi and record the net concentrate and permeate flows. I also usually run all the permeate back through the membrane as flush at the end of every day to keep it as clean as possible.

My sap usually runs 2.5% sugar or higher but your estimate is about right. I like to run about 4 to 5 hours including cleaning. I set up my RO to feed concentrate directly to my evaporator. I don't like to store concentrate and I definitely don't like to reprocess it through my filter as the snot in the concentrate can foul the filter pretty quickly. Hope this helps.

Dave

[BreezyHill]

Bowhunter,

BreezyHill (Ben) indicates you are the godfather of RO DIY. As such, your advice is golden.

I notice your signature details indicate that your RO does 18gph with a 2.5"x40" (Axeon?) NF4 (-2540?) (rated as 680gpd (i.e. 28.3gph) permeate w/ 15% recovery at 100psi) membrane, Using your 18gph quote and the spec ~140gph Procon pump feed flow rate, I calculate you are operating at a ~13% recovery rate (i.e. 18gph / 140gph).

Question 1: What type of circulating pump do you use to feed the 140gph (2.3gpm) Procon high pressure pump? Any issues with your pump choice?

Question 2: Why did you select the NF4-2540 ? How would the XLE (NF5-2540) membranes compare for maple sap concentrating ?

Question 3: What flow meters do you use to monitor the 140gph (2.3gpm) feed flow and the 18gph (0.3gpm) permeate flow rates? Is the scale sufficient to distinquish changes in permeate flow? I assume that during cleaning/rinsing mode, your permeate flow would be much less (almost nil) since you open the concentrate needle valve to increase concentrate-side flow rate.


I notice you had 71 taps on buckets in 2015. In my area, on a regular sap flow, I get ~1 gallon 2% sap per tap. With this in mind, I would think that if your 71 taps produce 1 gallon sap per day yielding 71 gallons of 2% sap, then your 18gph RO can reduce 71 gallons of 2% sap to 18 gallons at 8% in roughly 3hrs. Do you achieve this - or am I missing some important additional consideration?

???Not sure how that came about but what ever.

[Wizbi]

BreezyHill and Bowhunter,

I took the liberty to "color" with the word "godfather". I believe in an earlier thread response, Ben suggested to check with BowHunter - identifying how BowHunter had offered him good advice on cleaning solutions, etc, It is obvious from scanning the last several years of RO forum entries that Bowhunter has definitely been a prime responder. I appreciate all the advice. I want to get this right the first time.

I have been alerted to potential shortcomings in using either Aquatec or ShurFlo pumps in these RO systems. Both companies tech reps quickly identify the brush wear life of these pump motors can't handle long continuous operation at 1A current levels. I am concerned that I am forking over $ for a diaphragm pump that will not last for many years. Both reps discussed brush wear (carbon powdering) and that they are better fitted to intermittant operation and NOT recommended to bear short power cycling iterations. That said, eliminating the feed supply pump, was one of my considerations. Counter concern is the design limitations when procon pumps are input-starved.

I am wondering how recirculation plumbing can be designed to best draw in new sap, while eliminating a feed pump. How is the Procon high pressure output recirculted to low pressure input? Is there a need for a check valve in the recirculation loop, or do you just spray into a holding tank?

How is sap prefiltered (~5micron) without using a 15-20psi feed pump and filter cartridge?

For BowHunter or others: How did you plumb a recirculation loop? Procon 140 Series 4 has 1/2" lines. Do you recirculate with, say 3/8": lines.
Also what type of tank do you use attached to the recirculation loop, and with what type of head pressure/height?
Thank you in advance,

[briansickler]

https://www.youtube.com/watch?v=m_fu2bPPwqQ

https://www.youtube.com/watch?v=8YFmc2a50To

[Wizbi]

https://www.youtube.com/watch?v=m_fu2bPPwqQ

https://www.youtube.com/watch?v=8YFmc2a50To

Both U-tube examples from Steve Childs at Princeton utilize a shallow well pump as a means to feed the procon pump.

Bowhunter uses a design that eliminates the need for the feed pump altogether,

I am interested in how Bowhunter addresses filtering the incoming sap before ithe sap gets into the recirculation looping and how the recirculation is piped...

[bowhunter]

First of all there is nothing wrong with using a booster pump. I just choose not to use one because it makes the system more complicated and adds another component that can fail. A booster pump alone will not guarantee that the ProCon pump is always supplied with sap without the use of pressure switch(es) to shut the pumps down if the filter plugs, the feed tank goes empty, the booster pump fails or trips, etc, etc. I usually don't leave my RO running unattended so it doesn't have many opportunities to run dry. I'm retired what can I say.

I have a simple sketch of a single membrane, single pump system that I use, but unfortunately I can't seem to attach it to a post on this forum. I usually send it by e-mail to anyone who's interested. I'll verbally describe the system and I'm happy to answer questions or send you a copy of the sketch, etc. Or I'll post a pdf of the sketch if someone can tell me how to do it.

System description:
1. I use a 55 gallon drum as a feed tank and I have about 4 feet of elevation between the bottom of the drum and my Procon pump which is on the floor. I have my RO mounted on a hand dolly so I can move it inside my garage when it's not in use. That way I don't have to heat my sugar house.
2. My pump, membrane housing and needle valves are all 3/8 inch and I use 3/8 tubing to connect everything. I try to stick with the connection size on the equipment.
3. Sap flows from my head tank through a 10 inch 5 micron filter. I collect all my sap with buckets so I filter my sap before pumping into the head tank. I don't use anything elaborate for a sap filter just a syrup pre-filter. It seems to work fine. I also never run concentrate through my pre-filter. I had a lot of problems with snot forming on the filter and plugging it pretty often. Last year I only had to change my pre-filter a couple of time and the fouling was very gradual.
4. The sap flows from the filter to the ProCon pump suction. This suction tubing is tee'd and the concentrate recirculation ties in from the needle valve used to control back pressure on the membrane. The ProCon pumps generally have about 6 feet of lift meaning they can lift liquid as long as they stay liquid full. THEY CAN NOT BE RUN DRY FOR VERY LONG.
5.From the pump the sap goes into the membrane housing.
6. Concentrate from the membrane housing outlet is tee'd to the pressure gauge.
7. The concentrate then goes though another tee and splits to two 3/8 inch needle valves.
8. Net concentrate flows through the concentrate needle valve and through my Blue White Rotameter and into my evaporator. I really don't like to store concentrate since time isn't an issue for me.
9. The recirculation concentrate flow passes through the needle valve used to control back pressure on the system and into the tee going back into the ProCon pump.

If you're concerned about the ProCon pump I think you have two or three options to protect it. You can keep a spare pump which isn't too expensive. Second you can try and find a switch to shut the pump down on low suction pressure. I like the third option, but I haven't tried it yet and that is put a pressure switch on the pump discharge with a manual bypass switch in parallel with the pressure switch. You close the bypass switch to start the pump and once the pressure is above the set pressure you open the bypass switch. This way the pump shuts down on low discharge pressure and stays down until you manually close the bypass switch. I would set it for something like 75-100 PSI. This should shut the ProCon down in plenty of time to prevent damage. This option is probably the lowest cost option because if you use a booster pump you still need to add a pressure switch to shutdown everything.

That describes what I do and I would be happy to clarify anything I've said it it doesn't make sense.

Dave

[Wizbi]

12000

I have attached a diagram that I think matches BowHunter's described flow.

If this is a match, then I have an observation about the "snot" not forming on the filters.

I have to believe that whatever causes the snot is in the concentrate. Directing the concentrate into the suction line (teed after the 5u filter) instead of back into the feed tank does keep the snot from being caught by the filter. Snot is snot - it is still there, but where does it go then ?

Having the feed tank 4ft above pump translates to ~1.8psi head at the pump. I wondering if back pressure on the 5u filter due to the concentrate flowing into the suction line keeps unwanted particles from hard-lodging into the 5u filter. This can be viewed as a benefit of teeing into the suction line. Likely a reason why the 5u filter didn't clog as fast. In the end, the important thing is that the sap is one-time 5u filtered and that no additional particles can enter the recircultaion loop.

I am trying to keep inmind that if the RO is operating at ~85% concentrate flow to net flow, then the procon pump will still be drawing about 15% of its input from the feed tank. Does this make any sense? I am interested in understanding the flow and pressures in the suction line. ~200psi at input to concentrate needle valve, 85% of which is flowing to suction line and mixing with filtered sap from feed tank. How does that pressure taper off as it approches the input to the procon pump and the backside of the 5u filter?

I was leaning towards concentrate recirculating into a feed tank to effectively remix. My thinking is that the procon pump draws from the net remaining sap solution. I guess it is important to know the ratios of the 2 needle valves.

Details, details, details..... Are there some additional dynamics I am overlooking?

I am assuming that the needle valve flow to the evaporator is set relatively much less than the recircultaion needle valve. Likely drip trickling into the evaporator to keep evaporator levels up. ?

[BreezyHill]

My unit is a Memtek...antique...it was model year 1982. The pressure pump is a 5 hp piston pump with a 1.25' outlet that is reduced down to 3/4 to feed the membranes. The recirc loop is fed into the pump prior to the piston pump and is thru a 1/2" copper line. This unit has a sap temp gauge and it is usually between 42 and 50 degrees.
Snot is often bacterial growth of the concentration at this higher temps toward end of season.

My 1 hp feed pump runs around 50-60 psi unless the filter is plugging and then it drops on the gauge to 25-30#

Spare parts in sap season are a must. Nothing worse than having sap sitting and your RO is down. My big truck will only haul 2000g and I don't have time to run to a buddies so he can RO it over night. He offered but I declined.

Took about a day to put in the new feed pump and get it up and running. Longer if I had to order it.

[moeh1]

Does anyone have a good source for Flow Meters in the range of .1 to .5 gpm ?

My RO system will be very small, membrane is rated 225gpd (0.16gpm) at 100psi. I understand this translates to ~(0.31gpm @ 200psi). Am I correct to think that a 0.2 to 2.0 gpm flow meter not have the fidelity to measure 0.1 to 0.3 flows. Seems like only 15% of the readout range would be used. I would think I need more visibility in the 0.05gpm to 0.5gpm range. Dwyer makes a .1-1.0gpm for ~$96.00. Anything else being a better match for 0.3gpm ?

The ones I linked to on EBay are GPH, not GPM, flow rate is a good match for what you are looking for...

[Wizbi]

BreezyHill,

2000g of sap. WOW! Thats 8 tons. I can't even grasp the collection processes you employ.

As an ultra-small scale operation, I am wondering how to plumb eliminating a feed pump altogether - like BowHUnter describes. This can save upwards to 20% of total costs for an operationsl small scale DIY RO system that can yet attain 200psi+ and yield 12%-15% concentrate levels.

[Wizbi]

Was wondering that if rotary vane pumps have constant flow, why is a net flow rotatmeter really needed? Doing the calculations, for instance, there is not alot of difference between the inlet flow of a procon 140 discharging at 250psi verses being open. About 10gph (i.e.0.17gpm) between the two extremes. This seems to be the case for all the procon pumps, comparing their lower limit (open) and upper limit (250psi) flow rates.

What can you infer about the net flow by reading a net-flow rotameter that you can't know by observing the pump's outlet pressure (going tno the RO membrane) ?

I would think the readout on the rotatmeter would not adjust much at all. Isn't the more important measure the permeate flow and how it changes over the processing timeline ?

[BreezyHill]

BreezyHill,

2000g of sap. WOW! Thats 8 tons. I can't even grasp the collection processes you employ.

As an ultra-small scale operation, I am wondering how to plumb eliminating a feed pump altogether - like BowHUnter describes. This can save upwards to 20% of total costs for an operationsl small scale DIY RO system that can yet attain 200psi+ and yield 12%-15% concentrate levels.

If you had your pump on the gound and the concentrate tank above the vessel depending on what size vessel you cound easily have a tank at 4-8' above the pump. Not sure of the pressure drop across the smaller mbs but on a 4"x40 xle it is 13 psi. so you can elevate the sap with the pump.

Las season we ran for 3 days straight. That sucked when the RO was down. That was on over 600 taps; this season we plan to shoot for 1200 and have the one bush all retubed and tapped on the farm.

The rotometers we use in the feed mill only read gallons of total flow. Rotometer was a brand name of net metering device. Our big one would do 400 gallons a minute on the molasses truck thru the 2" delivery system.

Try looking at sprayer meters. The older units used a Red Ball meter. Plastic ball in a flow meter for each of the spray nozzles on a sprayer head. Often this were without the calibration stickers but one could calibrate easily and use a perm marker to mark the tube.