Older Memtech Passing sugar

[Quabbin Hill Farms]

I have an old Memtech RO circa 1980's that i purchased last year never really got it up and running but this year I did but i was getting anywhere from .09- 1.1 sugar passing through in the permeate. The membranes were new last year Filmtech XLE 4021 the unit has 3 4" x 20". I could get anywhere from 6.5 to 7.2 concentrate at one pass.

Just wondering if anyone else has a similar unit and see this issue. I had new PVC connectors machined to connect the the membranes to the bottom cap because i thought they were the culprit. I was able to run the permeate back through but was still seeing .01- .02. Can the membranes be checked to see if they are letting sugar through? They are fairly new only have about 10 hours on them.

Thanks any help would be appreciated.

[wiam]

When I was passing sugar with my old Memtek it was from a cracked adapter. Sounds like the one you replaced. Check o rings there and on the plug/cap at top. Pretty much has to be either of those locations or it is the membrane.

[bigbucksrule]

I likely have the same model Memtec RO that you have and the 3 - 4" x 20" posts were replaced by 1 -4" x 40". Unit works great, and I have processed up to 7000 gallons of sap in a year with it. Regularly go from 2% to 12% with some recirculation.

Have you checked the brine seals for damage and/ or made sure all 3 seals are installed the proper direction?

The brine seal on my membrane is getting old and stretched and I bought replacements for $4.00/ each. This is a relatively easy check and replacement on my unit would take 10 minutes.

[WMF]

Bad or missing brine seals won't cause sugar passage. Do the pressure vessels have aluminum end caps? SBS pits aluminum and this is usually where the problem is.
Check the permeate port area of the end cap for pits or rotten aluminum. Sometimes you can machine in a new oring groove in the adaptor to match up to a good spot in the end cap.
If it has multiple vessels separate the permeate streams and check each individually to see if only one has problems.

[BreezyHill]

Greg,
That is the same problem I had. The issue I had was the pump in my 1982 is to large for two xle 4040 membranes that were run in series. I spoke at length with a Dow engineer to figure the issue and my issue was membrane flow rates.

The engineer said I have to have no less than 3 gpm of concentrate flow away from the membranes or risk passage and quicker membrane fouling, no more than 14 gpm of flow thru the membrane or risk passage of sugar. So I have to redo my system with another pair of membranes that are parallel to the current two that are in series and plumb the new two in series also. I can also add another membrane in series as the pressure drop is only around 13 psi after each membrane and increase the permeate flow a fair amount.

What I have to do now is to run at a lower pressure amount and watch the flow meters. I bought a refractrometer to quickly check the permeate for sugar and adjust the pressure down as needed. On a pressure adjustment the affect on passage is immediate when dropping 10psi. I often come up to 300 for the first 3-4 hours of running and then need to drop 10 psi ever 1.5 hours there after. The first day on the new branes was a head scratcher...we checked everything from brine seals, orings, system lines, etc. Finally start the machine on low pressure and slowly worked it up until it started passing sugar. Then I called DOW. The guy was great but it is hard as they work mostly with water and salt. What we keep is their waste product. permeate is their product. So it was a little tough at first to get him onto the right page of thinking but he came around.

Not sure the pumps in your unit but I have the 38E and a 3/4 High flow SS feeder pump. The feeder is new this season as the other feeder froze when we went to 6 degrees the first week of this season after we had started running and my in unit heaters popped their breakers.

This pump made my issue worse as it supplies even more to the 38E piston pump and I can now hit 400 psi by turning the pressure valve and leave the concentrate valve wide open. My book says I have a 250 without the recirc pump but have a bypass system. I know this was a special Demo unit as it is noted in the book and we were the last stop of the season and my dad bought the unit of the demo trailer. They changed the piston pump after the first one failed the next season.

If you are looking for original flow meters let me know as I have to change mine as they don't go high enough to meter the unit with these pumps and membranes. My concentrate only goes to 2gpm, the permeate to 5 gpm, sap in is also 5 and the membrane recirc is only 30. Each of them is past the calibration points at different settings. Currently the permeate is the only one that is useful. RO membranes have certainly come a long long ways.

So what pumps do you have and you are running the 20" branes? If you are still running you should try running them parallel to see if that helps. If you have to much flow splitting the flow should help or stop the issue entirely. It is just a shame to waste all that capacity and not have another set of branes to remove more water if you have the ability.

Ben

[Quabbin Hill Farms]

The membranes are only two years old so I would guess the brine seals are OK. Where did you purchase the new post and membranes and what kind of dollars did you have to put out? Is the new post in a SS post mine has the three fiberglass ones with the three piece brass rings to hold them in place. what kinds of flow rate and pressures do you run at?

[Quabbin Hill Farms]

Yes mine has the aluminum end caps and yes they are badly pitted. Don't know if anyone makes a plastic version of those caps.
Thanks for your reply.

[BreezyHill]

The membranes are only two years old so I would guess the brine seals are OK. Where did you purchase the new post and membranes and what kind of dollars did you have to put out? Is the new post in a SS post mine has the three fiberglass ones with the three piece brass rings to hold them in place. what kinds of flow rate and pressures do you run at?

As I recall membranes were in the 245 ea range and the vessels were around 140 ea.

SS with 3/4" ports. Pressure depends on the prefilter. When it is a new filter I can not go very high as the flow is to much. Max is 200 psi. When the filter has had several hours on it then I can get up to 280 with no issue I was able to go to 350 one time when I was running cloudy sap on a warm day at as the tank batched I had to drop about 15 psi per 20 minutes to keep from passing sugar,

I was running at 30 GPM when I first put in the new branes and vessels and didn't realize what was happening. I was upto 1.5% passing so I would send the permeate to another tank as we worked to get the unit working right.

With two more branes I will likely not be able to get the pressure up over 350 but I should have doubled plus a little from where I am on permeate now.

My best permeate rate was just under 4 GPM and as the branes would loadup I would get to as low as 1 Gpm on the permeate during the end of season on sap that was cloudy and toward the end of a batch. When I switch back to raw sap she would jump back up again after the raw sap flushed them for 5-7 minutes. Then I would turn up the pressure and get the permeate flow back up again.

[Quabbin Hill Farms]

OK thanks with my system I run it around 500 psi concentrate flows of .80 gpm and permeate at 1.2 gpm Which company did you buy your upgrades from.
Thanks

[BreezyHill]

Atlantic.

Running at 500 with the new branes really isn't possible for me as I will pass sugar at 2% or higher. The dow engineer tock a while to get his mind around what we do....it is backwards from making water from sea water. What we want is what they discard. After he was up to speed and thinking in reverse we decided the issue was simply not enough concentrate flow to keep the membrane clear. This season I found that running with the by pass valve closed and not recirculating extended my run time and allowed for higher psi...this gave me higher permeate flow also.

My best investment this season was a 0-32 refractrometer for $25 at the door. Great unit and way faster than the hydrometer. I use the hydrometer to calibrate the first time and then just used condensate after that to check the zero.

It really is surprising how long it takes to flush the sugar out of a membrane when you switch and are flushing it out with permeate. I shutter to think of all the sugar we sent down the drain over the years. The longest this season was 15 minutes to get to under 1% and that is running at 6-8 gpm out the concentrate line. When she starts to drop it changes pretty fast...within 2-4 minutes typically to go from 3 to less than 1%. Getting down to 3% just takes so long...but that is a lot of raw sap reclaimed.

I am hoping that I can do a flush more often with increased branes on the unit to keep the productivity up and the end flush time minimal.

One other thing I noticed is that on my unit it says 30 minute wash cycle. I did a 60 minute one time and it made a fair amount of difference in flow rates. The Engineer recommended limiting washes to keep better brane life. He felt 3-4 days with good flushings would be plenty. To often and you can make the membrane attract sugar.

Next season we will be setup to do warm water rinsing. Adding an addition section of SS Dairy pipeline to the steam duct to preheat 300 gallons of permeate. Small pump on a temp sensor to circulate til it reaches 90 degrees. Set the RO to autopilot and start the flush and then go to bed if it is late.