permeate .7 ?

hello Traders,maybe you can help me though this. ran my ro today for the first time. on sap. set pressure at300 with recirculating needle valve open . permeate meter was running at 3.5 and concentrate meter at .5. almost right at original owners marks on flow meters. permeate was a little higher. sap sugar was 1.3% going in 5% coming out concentrate side, .7% coming out permeate side? is this normal? it's a waterloo- small 300gph antique. I shut the ro down when I realized it. maybe 100 gallons of sap. it does have a lot of leaks, one's pretty big at 300 psi. feel like i'm missing something. any pointers would be much appreciated.

Seems like you are passing sugar. Mine reads negative .5 which leads me to believe my hydrometer is off a little :D

300 psi seems high to me to be running at but I'm not familiar with that machine and it's specs. My machine says not to exceed 225 psi, and I rarely go above 150...

wnybassman,
it does seem like I'm passing sugar. but where? bad membrane, o-ring , membrane not seated right, plug and two little O-rings on it in the end of membrane are the only things that could cause this .correct.

miboss,
says on front panel not to exceed 500psi . my flow meters don't level out until 200psi unless i'm doing something wrong. I did say- ran my ro today for the first time. on sap.:)

You did say it had a lot of leaks, I am assuming on the outside. Perhaps there are leaks on the inside as well.

It does sound like the membrane is passing some sugar if your flow meter readings are correct. You should be seeing 8-9% concentrate instead of 5%. It is very difficult to measure sugar content accurately down between 0-1% but 0.7 is pretty high relative to 1.3% sap. You could have 3 possibilities. 1) The membrane could be passing sugar because of it's age and being cleaned under too high a pH or too high temperature or the pressure it just too high at 300 psi. 2) the membrane could be physically damaged by over pressure on the permeate side at one time in the past or 3) the small o-rings on the inside are damaged and need to be replaced. I guess there could be other possibilities but these are the most likely. I would try running the pressure at 225 to 250 psi. A nano-filtration membrane such as an NF 270 that has been cleaned several times may pass quite a bit of sugar at 300 psi. If that doesn't help you can replace the small internal o-rings. If it's still passing sugar at the lower pressure and the o-rings are new then it's most likely a damaged membrane and the only thing you can do is replace the membrane or live with the problem.

If the RO was running correctly and the membrane(s) are in good condition the permeate should be at or very near 0.0 sugar. I suspect the membrane(s) need replacing but it could be another issue. Could be a bad seal too, allowing some concentrate to leak into the permeate side, but the membrane(s) are most likely the issue.

It sounds like you're passing sugar. Most membranes can handle 600 psi and a lot of the older professional RO's can run at up to 500 psi. Mine has a high pressure switch that shuts it off at 500 psi. What membrane do you have? If it's a Dow NF-270 it can pass sugar at higher pressures and concentration levels. Did it get damaged by drying out or freezing? Is the U-cup installed properly, if it uses one? Is the big O-ring seal on the membrane facing the right direction? If you find that you need to replace your membrane, or membranes, if you have more than one give MES a call. I bought two of their MS2 4" membranes for $215 each. They flow fast and don't pass sugar. I've been running mine at 300 to 400 psi and I don't think running your's at 300 psi is the cause of your problem.

well the two membranes in there are osmonics desal model-dk4040f1023. says vista California on them. I could not find them on the web. just like my ro. too old. I do remember the big o-ring on the outside was in good shape. apon opening last fall I did replace 2 of the 4 little O-rings as I could see pieces of them on top of the membrane.


Russell , Is the U-cup installed properly? I don't remember seeing one where are is it located? did you need to by the plug separate or does it come with membrane?

thought about it all night and if I have to tare this thing down I just as well put new back in. it's just as much work. as I tare down I will keep an eye out. thanks for the replies.

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Originally Posted by amasonry

well the two membranes in there are osmonics desal model-dk4040f1023. says vista California on them. I could not find them on the web. just like my ro. too old. I do remember the big o-ring on the outside was in good shape. apon opening last fall I did replace 2 of the 4 little O-rings as I could see pieces of them on top of the membrane.


Russell , Is the U-cup installed properly? I don't remember seeing one where are is it located? did you need to by the plug separate or does it come with membrane?

thought about it all night and if I have to tare this thing down I just as well put new back in. it's just as much work. as I tare down I will keep an eye out. thanks for the replies.

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On my RO the U-cup slides over the big seal on the membrane. Because of the design of the pressure vessels some don't use them and the membrane seals against the pressure vessel directly. The plug that goes on the end of the membrane is sold separately. I suggest getting the cap style plug, not the one that goes inside the nipple. MES doesn't have the Cap style plug, get those from Lapierre. They're about $25 each but they work on any membrane with a 1/2" nipple. I'm assuming that you have 4" membranes.

hey traders, well though i bring back this old thread. rebult the old ro. new membrane (mes), new housings (pentair),and fixed many leaks. now she runs great. but i'm alittle short on experience. mabey someone here could make some sents of these numbers? so i started with .5% sap that was 51 deg. then turned up the pessure 350psi.i was getting 3% concentrate. flow meters read 4.5 permeate and 1.25 concentrate. does this look right?

Changing 0.5% to 1% is removing half the water. So permeate flow would equal concentrate flow in that case. Going from 0.5% to 2% is removing 3/4s of the water, so ratio of permeate to concentrate would be 3:1. 0.5% to 4% is removing 7/8ths of the water, so the ratio would be 7:1.

0.5% to 3% is about half-way between 3:1 and 7:1, so maybe call it 5:1. You are running 4.5:1.25 or 3.6:1. Seems a little low, but depending on the accuracy of your measurements (especially the 0.5% value), you're in the right ballpark.

I suggest tasting the permeate. Most people can taste sugar as low as 0.2-0.3% . If you can't taste sugar, you're probably fine. If you still have doubts, take a gallon of permeate and boil it down by a factor of 10, then cool and measure sugar content, but divide the number by 10 to get the value of your permeate.

My only question is where are you getting .5% sap? Fall tapping or hand built sap?
I will not be able to help much as I dont own a R.O.
Regards,
Chris

hey sugarmaker, it was hand made this summer. just had to test it .

"take a gallon of permeate and boil it down by a factor of 10, then cool and measure sugar content, but divide the number by 10 to get the value of your permeate."
good idea. going to do that this coming season. last year i though my ro was ready ,but was not even close. so this year i want to be sure. thanks for the advice

Also make sure your test instrument is accurate. Make note that a hydrometer can be knocked off by dropping it into the test cup. It must always be lowered gently.