Did you really know this about procon pump self-priming?

[Wizbi]

I have just finished talking to 2 tech reps at Procon Products and have clearly been told the following. It has changed my entire RO system design - FOR THE SIMPLER. I am hoping this info helps others.

Prior forum threads have said that you need to be concerned about running the procon pumps dry. This is true, but is poorly stated advice - per the procon reps.

The reps say that the real issue with these rotary vane pumps is concerned with the tight tolerances on the vanes inside the pump and specifically how the vanes can become siezed when the pump is stopped or is stopped by some event.

They say that once the pump has fluid moving inside it for the very first time, then it is very important that the vanes don't stop because the fluid particles could cause the vanes to glue/stick and therefore cause the pump to sieze up. The vanes can sieze up when the pump cavity is permitted to loose fluid and fluid particles are permitted to dry in ways that glue the vanes up. They point out that if the vanes are permitted to become glued/siezed then a pump breakdown will likely occur in which the internal pump parts can shatter/disintegrate. They identify that the pump is designed for upto 10,000hrs of continuous use and is not really intended to loose its initial prime. Pump vane disintegration is a bad event!

They clearly said the problem CAN BE RESOLVED BY flushing the procon pump with clear water for a sufficient time to clear out particles or viscous moelcules PRIOR TO stopping the pump. In this case, the pump will then be ready to "SELF-PRIME" again as if it were the first time startup.

The reps also confirmed that the pumps are designed to self-prime within 6 feet of the feed port. In other words, as long as I have less that 6 feet of hose to my sap feed tank fluid level, I should not even have to consider using a delivery pump or elevating the sap. They clearly said 6ft was the max distance, because I wanted to clarify the difference of a hose going up and over a feed tank rim verses only dropping down directly into a feed tank.

In my RO plans, I want to use a 40gal drum as my sap feed tank, I am thinking that is is better to have my procon pump positioned near to the top of the tank and drop a 3-4ft hose down into the tank verses trying to use a setup that has to go up and over the rim of the sap feed tank (more distance and longer prime hose length (i.e 6+ft).

As a possible way to mitigate the procon pump from losing its fluid, has anyone thought of piping the pump in the manner indicated by the attached drawing. Sort of way to break the siphon in the event that the RO system starts to drain on either side of the pump. Pump would still be swimming in sap unless it was turned upside down.

11957
Does anyone have any thoughts or concerns to the contrary of this info?

[BreezyHill]

I was unable to get the drawing to enlarge but:
A supply pump is usually in the design to feed the pressure pump through a filter. On a new filter there is likely no issue but to take a less than new filter and run the risk of a mostly plugged filter caveating a pump...would not be a design I would use.

You can easily use a hole saw to put in a bung in the bottom of a plastic drum and have so head pressure from a full tank and shorten the feed line this way.

Ok I tried the pic again and it worked.

Since the pump is will have already had a prime it will evacuate all the fluid from the feed side until it looses prime and then it should have only a small amount of fluid on the outlet side. Still allowing a cavitation issue.

A float switch in the feed tank to a power supply relay will cut the pump power and save the pump. Many of these on ebay also for very little $$$

[maple flats]

If you mount it close to your head tank, how do you plan to flush it with permeate before shutdown? The permeate would be your water to "clear the pump".

[Dennis H.]

With out a feed pump how are you going to get 1st prime to begin with?

Next question, which model Procon are you planning on using? Cause my series 5 Procon clearly states in the manual that it needs at least 20 psi inlet pressure at all times.
So I see no other way than using a feed pump.

[Wizbi]

Series 2, from a McCanns Carbonator, 100gph. I will be small-scale and can get these cheap from ebay. The engineers at Procon did clearly indicate priming on the series 5 is the exception. That is why I am avoiding the series 5 model.

The reality is moving 30-40gal containers (240lbs-320lbs) around instead of paying more for pump, motor, sensors and a RO storage tank. My concept is that I would move the sap, or permeate H20 into position instead of dealing with extra pumps, motors, etc.

Again I will be small scale - 120-200gpd max.

I've been told that the priming within 6ft will repeat itself on successive startups - as long as the issue of the vanes getting stuck is managed properly. McCanns carbonators are started and stopped all the time. Their m.o. is that seltzer water is being cycled through their procon pump so the vane-siezing issue is not a common problem. I read some maintenance advice for McCanns carbonators that indicates you can revive these procon pumps if they get siezed by soaking them in a dilute soultion of citric acid which helps to unglue the vanes in the event they get fused by dried-up sugar. Anyone know of this method?.


I was planning to filter the sap separately - one time. Most of the maple trader designs have recirculated cocentrate passing back through the "prefilter" on each pass. My idea is that I will still use a low gph pump and 5 micron filter to initially filter the sap. I sortof don't understand why everyone's designs route concentrate back through the prefilter. Seems like a design parameter that leads to more costs than is necessary. Once the major contaminates are removed - they are removed. Why put more wear and tear on the prefilter. Plus the procon pump won't have to prime and operate through the prefilter passage.

Does any of this make sense?

[Flat Lander Sugaring]

yes they are correct you dont have to have a feed pump just like fluid O teck pumps. But I will tell you, you will NOT reach max pressure of 250psi with out a feed pump which would also be saying you wont get your maxiumum GPH.

I did that once no feed pump gravity feed less than six feet tank was 2 to 3 ft higher than filter.
I would spend the extra 160 for a feed pump and know that little unit wont run out of sap because the head pressure drops off because the filter starts to clog.

Just my .5 cents worth govt took the other 1.5 for welfare rats, Cuba, Pakistan, Afghanistan, Israel, Syria,

[Wizbi]

What got me concerned at first is trying to match a feed pump to the HP pump feed requirements.

If procon pump needs 2gpm incoming, then the low pressure supply pump must be able to provide that. This gets me into the choosing between something like a shallow well pump (with it's high amps and 220V parameters) and a buffered storage tank - or using something like the Aquatec 5500 series diagphram pumps. Both involve costs, plus what about worries about bacteria. My RO will be used 1 time per day. I am concerned about flushing between uses.

[BreezyHill]

flushing between uses is by way of the permeate being run back thru the system.

Good point on refiltering your sap, but for me it is easier to refilter and not worry tha something will hurt the pump rather than score a pump.

I have a well pump that I think came from tractor supply that is 110 1hp for a water well on the farm. If this pump feed a length of 4" pvc as a pressure vessel you would have a built in pressure tank to feed the procon.

LMFAO ...Great one Flat Lander!!!! To bad it is the truth!

[Wizbi]

On the topic of having enough gpm as input to the procon pumps: it seems to me that considering how procon pumps work, matching a pressure pump flow rate to the input requirements of the procon pump is critical.

The procon pump is at risk if there is not enough input fluid. I would think that there are procon mechanical considerations if there is way too much feed fluid also. In a closed loop config in which some constant volume pressure vessel (like a large PVC tube), there is hardly much difference in the amount of water at 1psi verses 40psi. If a buffer tank is used then tank volume will change keeping the pressure near constant (diaphram in tank doing this). So the story goes, the low pressure feed pump is likely going to have to run continously to keep up with procon pump or else a large buffer tank will be necessary to reduce the duty cycle of the input feed pump.

Are shallow well pumps or transfer pumps designed for continuous operation for hours on end?

These are concerns that keep me coming back to having an open loop design in which the procon pump is merely always swamped and spinning away. Such as a right-sized tank that drains directly into the procon pump. Then the design parameters shift to how to insure the feed sap level is always high enough to have the procon pump swamped.

Maybe the experts will advise to select a low pressure pump that is able to keep up with the procon pump AND use a relatively small size buffer tank to attenuate the input pressures fluctuations on the procon pump. Same sort of thing occurs in an open system design - procon system doesn't experiance any real pressure fluctuations unless the feed tank runs dry!

[Flat Lander Sugaring]

I have been running the sprinkler pump from HD for 3 years now i think its 720GPH 1HP stainless pump. With that I can surpass the max pressure of the stainless vessels and blow the end caps right off no problem "I recommend not doing the end cap thing".

[Wizbi]

do you use a pressure tank or do you direct feed your procon pump ?

[Flat Lander Sugaring]

if your last question is to me, no pressure tank sap comes out of a 500 gal milk tank to feed pump through filter to High Pressure pump. I have two low pressure switches, one shuts down high pressure around 30 the feed pump shuts down around 15.

each night rinse system with perm. and all good for next day

[Wizbi]

Flatlander,

Am I correct to read that your low pressure pump flows directly through filter into the high pressure pump?
If so, then how well matched are the ouput flow rates for your low pressure pump and the input flow rate of the high pressure pump?
Am I making too much of a deal about being concerned about starving the high pressure pump?

Also how much concern should I have about the low pressure pump having a much greater flow rate than the high pressure pump ? Is it hard on the low pressure pump to have flow resistance on its ouput side? Is is hard on on the high pressure pump to greater than it's needed input flow? Or are these pressure not really of any significance? A sort of feast or famine type of question.


Thank you for helping me understand.

[Super Sapper]

If you size your low pressure pump to be a little higher flow rate than your high pressure pump you should be good. Make sure you size it to compensate for fouling of your filter and the reduced flow rate from that. If your feed pump puts out more that the high pressure pump it is the same as throttling a valve to adjust flow and will not hurt the pump. restricting the suction side will damage the pump but the discharge side is ok.

[Flat Lander Sugaring]

pretty much what supersapper said. Our small high pressure pumps mine does 316GPH at 250 psi, my feed pump does 720GPH at around 80 psi. I change the filters often

Now my new ro that I tinkered with last year has a 601GPH 250 psi I can here vanes start rattling when filter starts to plug, so Im going with a 20"x2.5" filter 1" inlet and outlet.
Im ok with this stuff but,
Hit up bowhunter, he is awesome with this kind of stuff running numbers.

[Wizbi]

On the topic of sizing pumps, etc.

Is there a way to identify how RO membrane's permeate flow rate will change if one increases feed flow for the same RO operating pressure?

For instance, the membrane I am looking at is spec'd as 360gpd at 100psi with 15% recovery. That works out to be a 0.25gpm permeate flow for a 1.67gpm feed flow. Now, if I wanted to use the same membrane, but with a higher volume high pressure pump that is 3.3gpm, again at 100psi, how would the permeate flow change? Twice as much flow across the membrane, but the same pressure. Will there be expected losses due to the resulting increase in turbulance?

If the membrane is spec'd to have a max flow rate, then what expectations on performance can one count on specifically due to increase feed flow rate?

This membrane has a 6gpm max spec. Is it likely that the best permeate flow rate occurs at the manufacturer's spec'd 1.67gpm feed rate and the tradeoff then is reduced permeate flow for increased feed flow?

The related topic seems to be what happens when pressure is adjusted. I believe permeate flow changes proportionately with increases in operating pressure upto a point where membrane fouling occurs.

[BreezyHill]

I can only talk from my experience: but as I increase my pressure on the system the flow rate does increase fairly quickly. But if I exceed the max flow I passed sugar. I usually could hit the max rate of the xle 4040 right around 235 after it was cleaned, but as it started to foul the flow rate would drop off slowly. An increase in pressure would compensate for the drop but it would usually continue to foul faster and faster. Since I was batching I would push until the batch was done and then flush the brane with raw sap and start all over again. I would never get back to the original flows and pressures after it had started to foul until I would wash it. But the reduction was not more than a couple percent or at maybe 10 psi higher to get the same flow rates.
This season should be a better base line since I will be more matched to the pumps ability with more vessels.

Have you visited Dow's site and downloaded the xle charts and specs data. They did have a graph that explained those number to some extent.

[Wizbi]

I track on the pressure increase, assuming you are accomplishing it by turning your concentrate adjustment valve so as to restrict flow more.

You indicate that further RO membrane fouling has an effect to reduce the permeate flow rate. I would have to concur. More pressure should squeeze more water through the membrane to a certain point, but would also begin to foul again, and sooner.

Given that scenario, and if you could snap a finger and change out your HP pump to one that doubles the feed flow rate for the same pressure - would you expect any significant change in the permeate flow (doubling the feed flow, keeping same membrane and using the same operating pressure) ?

[Super Sapper]

First I would like to say that my experience with RO's is mostly from the early 90's and intermittently since then. I am a wastewater operator at a dairy plant so I also have experience with pumps. Permeate flow is created from restricting the flow and causing the pressure to increase and force "water" through the membrane (higher pressure less flow). At a constant pressure the permeate flow rate should not change with total flow rate. A larger high pressure pump will have more total flow but should have the same permeate flow at the same pressure. This will create a higher velocity across the membrane and keep it from fouling as quickly and your permeate flow will not drop off as fast. As you increase pressure you reduce your total flow rate and increase your fouling rate. A larger pump will work better as long as you stay within the specs of the equipment.

[Wizbi]

I appreciate good, founded advice. Thank you.

[BreezyHill]

I track on the pressure increase, assuming you are accomplishing it by turning your concentrate adjustment valve so as to restrict flow more.

You indicate that further RO membrane fouling has an effect to reduce the permeate flow rate. I would have to concur. More pressure should squeeze more water through the membrane to a certain point, but would also begin to foul again, and sooner.

Given that scenario, and if you could snap a finger and change out your HP pump to one that doubles the feed flow rate for the same pressure - would you expect any significant change in the permeate flow (doubling the feed flow, keeping same membrane and using the same operating pressure) ?

To some extent. The Dow guy I talked with said increasing the flow away from the mb would reduce the fouling rate....this is more gallons through the flow meter of gallons pumped or circulation but it would not neccesarily increase my permeate flow.

One needs to remember we are not using this mbs as originally designed. What we want is the throw away product for their original design. This are desalinization mbs. So when we want more sugar we are really looking at decreasing the concentrate flow to remove more water for discard. For a water plant they just pump more sea water through the mb and it is at no appreciable cost. For us it is more water that we need to pump back through the system to get rid of.

But one could make a case for a large pump on a VFD that you could press B and the pump will spin at full rpm and flush the mb of lodged sugar. Drives for small pumps are in the $150 range and would work well for that purpose. One could also adjust the drive to adjust pressure. As far as that goes with a bit of wiring and pressure transducer one could make the unit adjust its own speed to get the most out of a run cycle. Add in a sugar meter on the permeate and if sugar were to pass then it could do an auto flush cycle.

But now we are getting out of our budget perameters for many people; but the options really are all the way to a unit turning on and off as set by the operator and all one would need to do is manually change filter cartridges...set of several so that if output pressure dropped the unit would switch to a new filter housing by way of elec valves.

[Wizbi]

Sounds complicated,

The intent was to get advice on the tradeoffs of designing in higher flow rates. It sounds like it's pressure increases that increases permeate flow. Using a higher volume pump and/or causing more needle valve restriction are ways to design in more pressure. In either case, the flow rate doesn't directly cause permeate to happen - its the resulting presssure that affects flow rate.

I wanted to better understand the alternatives for selecting pumps for available membranes.

The flow rate also is important because a higher flow rate is the mechanism to sweep membrane pores to avoid fouling. I am hearing that 2-3x the rated flow rate is a good decision as long as it is still less than the max spec flow rate.

And a third consideration is to choose a right sized low pressure pump that can run continuously and is able to push through a prefilter and also keep the high pressure pump from starving.

Then, to do all this for the desired processing capacity.

I also want to operate only on 110V.

I think I have found a combination: filmtec 2521 RO filter (for its 13 pH cleening limit) with a procon 215 high pressure pump and an Aquatec 55x2 low pressure pump. Aquatec 55x2 can contiuiously output ~20psi in the ~3.3-3.68gpm range. Procon pump flow rate can be adjusted by needle valve/etc to output upto 250psi. All this should process 120gallons of sap from 2% to 12% in ~3 hours.

[Bainbrook Boiler]

Hi Wizbi -

I am also a small producer and have been using a small 4 x 150 GPD RO that was built using Hodorskib's design. We have been at 100 taps and are goiong to about 150 this year. The RO we have can't keep up and I was very interested in the questions you raised several years ago in this thread. Did you ever build the RO you seemed to have decided on and, if you did, how dos it run? Are there any things you did that you think work well and are there any things you would do differently?

Thanks
- Rich