CDL 600 Operation

[jbuck]

Hello fellow RO operators:

I have a new-to-me CDL 600 machine and have a question regarding the pressure control valves for the concentrate and permeate lines. I understand the principle of the RO, but am confused how you control pressure and flow with two separate valves. I'm suspecting it has to do with the re-circulation loop that it done in parallel to the main concentration flow. I have studied a friend's machine but am stuck on how to manage these control valves.

My question is this: if I want to be nice to the membrane (and machine) what is the preferred set points for those two valves? Both will adjust the membrane pressure and I'm assuming the flow as well - I've just never studied the affect on the flow rates while adjusting these valves. What are the rule-of-thumb targets for pressure and flow based on the way I want to run the machine and process a day's sap?

My operation plan is this:
average daily raw sap volume: 2000 gal
concentration target: 12% with two passes

Thanks for the feedback!

James

[markcasper]

Hello fellow RO operators:

I have a new-to-me CDL 600 machine and have a question regarding the pressure control valves for the concentrate and permeate lines. I understand the principle of the RO, but am confused how you control pressure and flow with two separate valves. I'm suspecting it has to do with the re-circulation loop that it done in parallel to the main concentration flow. I have studied a friend's machine but am stuck on how to manage these control valves.

My question is this: if I want to be nice to the membrane (and machine) what is the preferred set points for those two valves? Both will adjust the membrane pressure and I'm assuming the flow as well - I've just never studied the affect on the flow rates while adjusting these valves. What are the rule-of-thumb targets for pressure and flow based on the way I want to run the machine and process a day's sap?

My operation plan is this:
average daily raw sap volume: 2000 gal
concentration target: 12% with two passes

Thanks for the feedback!

James I'm kind of having a hard time understanding what you are saying? There really is no specific "set point" in regards to the valves. You basically turn the valves to match your desired pressure. The temperature of the sap has everything to do with that as well. If the sap is 10 degrees difference from the day before, you will not turn the valves identical from one day to the next because the temp will slow it down or speed it up. You need to go off the pressure gauge in determining where you set your valves, not a one size fits all approach. I don't like to run mine much over 325 psi, keeps the membrane healthy.....

[jbuck]

Mark,
Sorry for the meandering explanation. My trouble is that both valves will change the pressure, which I agree should be run around 300-325 psi. My question more directly is: since both valves influence the pressure, why are there two valves? How do they work together to produce adequate flow and pressure?
Thanks

[markcasper]

Mark,
Sorry for the meandering explanation. My trouble is that both valves will change the pressure, which I agree should be run around 300-325 psi. My question more directly is: since both valves influence the pressure, why are there two valves? How do they work together to produce adequate flow and pressure?
Thanks

Its been almost a year again, but going off the top of my head. When you turn your permeate valve clockwise, your high pressure gauge goes UP. You then turn your concentrate valve counterclockwise (this may be the wrong way??) to "tighten it up" or make it sweeter, since your doing that, your concentrate flow drops and the more you turn it,the more the pressure will also go up. So in essence, when you drop your concentrate flow (sweeter), you need to adjust your permeate valve to also lower in tandem, or you will get way too much pressure on the membrane. I would say there are 2 valves because without a concentrate control valve, you wouldn't be able to adjust the flow rate to match 1) your evaporator, and 2) your desired sugar %. I'm not much help I would say, I'm sure someone smarter than I will chime in.

If your running a 50/50 first pass, your concentrate valve and permeate valves are in a way different location than say if your running a 80/20 pass the first time, your flow rates are also lower with an 80/20 at the same pressure. The sweeter the sap going through, the slower your machine will be, thus that is why you need 2 valves.....to adjust to different sap conditions.

[mountainvan]

I never adjust the permeate valve, just leave it wide open. When I start the ro I set both lines to run between 5-6 gals/ minute and recirc the sweet back to the sap tanks, pressure is usually 250-300. The permeate goes in the rinse tank or ground or extra front pan to remove niter. When the sweet gets up to 8% I drop the concentrate flow to 1.5-2 gals/min, the pressure goes up to 400, and I switch the valves to send the sweet to the feed tank. Works for me.

[mellondome]

One valve controls how fast the concentrate flow is... the slower the flow the higher the brix. The other valve is to regulate the oressure in the vessel. If you restrict the concenteate flow... it will increase pressure in the membrane.... requiring you to reduce the pressure with the pressure valve. Its a balancing act.. which changes with temperature and how fouled the membrane is.

Once you set your concentrate flow rate, it will remain the same regardless of the membrane pressure. Changing the pressure will change the amount of permeate flow. Neither valve has any affect on recirculation flow for the membrane. Recurculation is done internal to the membrane housing with a dedicated pump.

[mellondome]

All you need to do is follow the instructions on the front of the machine. Figure out how much water you want to remove per pass. And i would recommend running between 300 and 375 for membrane pressure. After the machine has run 20 min... check your flow rates and pressure as they will change more in the first 20 min than it will the rest of the day.
Flow rates will vary between your first and second passes.

[ennismaple]

I never adjust the permeate valve, just leave it wide open. When I start the ro I set both lines to run between 5-6 gals/ minute and recirc the sweet back to the sap tanks, pressure is usually 250-300. The permeate goes in the rinse tank or ground or extra front pan to remove niter. When the sweet gets up to 8% I drop the concentrate flow to 1.5-2 gals/min, the pressure goes up to 400, and I switch the valves to send the sweet to the feed tank. Works for me.

This is how we run ours. First pass you'll probably get in the range of 5 concentrate and 5 permeate if you balance flows. For 2000 gallons of sap that'll run for about 3.5 hours to get down to 1,000 gallons of semi-concentrated sap. Dial the concentrate down to 2 GPM and your permeate might only go up to 6 GPM or so. That remaining 1,000 gallons will be gone in just over 2 hours, leaving you 240 gallons of concentrate to boil.

Doing 2 passes you need to make sure you look after your membrane. I would do a short rinse after the initial 3.5 hour first pass before bumping up the pressure for the second pass or over the course of the season your performance will drop.

[mellondome]

Draw back to running 50/50 is you will only go from 2% to 4% leaving you to go from 4% to 12%

It is harder on the membrane the higher the initial sugar is. Your better off going from 2% to 8% in the first pass... then 8 to 12% in the second.
These big ROs were built to go from 2 to 8 at 600 gal/hr @ 70 deg. in a single pass If you only want to go from 2 to 4 i a single pass ... save your money and biuld your own.

[Super Sapper]

Restricting the permeate flow does nothing except create added unnecessary pressure to the system and slows your total flow. An RO works by restricting your flow on the concentrate side and forcing the water (permeate) through the membrane. Adding restriction on the permeate side makes it harder for the water to flow through the membrane and reducung your efficiency. Pressure does no good if the water has nowhere to go or is restricted.

[huskyxp]

James,
I also have a CDL 600 and concentrate between 10-13% with two passes. I was told not to run your concentrate flow below 2 gpm, so after turning the RO on I set the conc. flow to 2 gpm and adjust the pressure to 300 and I usually have between 5.5 and 7 on the permeate flow depending on sap temperature. With that pressure and flow rate it will turn 1.6% sap to around 6% and that goes to another tank. When it is done with the first pass I would recommend doing a short rinse, like ennismaple suggested. Then I send the 6% back through again with the same concentrate flow and pressure and the permeate flow is around 3. I talked with CDL this spring at their open house and they said avoiding running the pressure between 325 and 375 because it is hard on the machine and recommended that I try running it around 400. I also wash my machine every day and don't have a decline in performance through the season and I ran 65000 gallons of raw sap through it last year. Right or wrong this is how I do it. Good Luck!

[markcasper]

Draw back to running 50/50 is you will only go from 2% to 4% leaving you to go from 4% to 12%

It is harder on the membrane the higher the initial sugar is. Your better off going from 2% to 8% in the first pass... then 8 to 12% in the second.
These big ROs were built to go from 2 to 8 at 600 gal/hr @ 70 deg. in a single pass If you only want to go from 2 to 4 i a single pass ... save your money and biuld your own.

Bottom line is that if you want to get rid of the most water in the shortest possible time, (i.e. lack of storage) then you do 50/50. Who says you have to go to 12? I run to match the evaporator on the 2nd pass. I'm not sure I agree with you on it being better running a higher % on the second pass. The 8% on the 2nd time is going to have higher bacteria and probably be quite warmer in temp. than the 4%, which can foul a membrane faster. My 2 cents.

[markcasper]

James,
I also have a CDL 600 and concentrate between 10-13% with two passes. I was told not to run your concentrate flow below 2 gpm, so after turning the RO on I set the conc. flow to 2 gpm and adjust the pressure to 300 and I usually have between 5.5 and 7 on the permeate flow depending on sap temperature. With that pressure and flow rate it will turn 1.6% sap to around 6% and that goes to another tank. When it is done with the first pass I would recommend doing a short rinse, like ennismaple suggested. Then I send the 6% back through again with the same concentrate flow and pressure and the permeate flow is around 3. I talked with CDL this spring at their open house and they said avoiding running the pressure between 325 and 375 because it is hard on the machine and recommended that I try running it around 400. I also wash my machine every day and don't have a decline in performance through the season and I ran 65000 gallons of raw sap through it last year. Right or wrong this is how I do it. Good Luck!

Why is it hard on the machine at 325-375? Never heard of that one before.