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Thread: RO Membrane Flushing during water production

  1. #1
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    RO Membrane Flushing during water production

    Question regarding RO membrane flushing during RODI water production. I have set up my system with some solenoids such that when my water reservoir is low it starts my RODI system. It initially opens a dump solenoid to dump the TDS creep water then proceeds to close that solenoid and open the one filling my container. Once the top optical sensor is closed, it does a RO membrane flush via a solenoid and virtual outlet for 2 minutes.

    Here is my programming which has been working well.

    StartFill ( a Virtual outlet)
    If Lo_ATO OPEN Then ON
    If HI_ATO CLOSED Then OFF
    Defer 002:00 Then OFF

    FINAL_FLUSH (a Virtual outlet)
    Set OFF
    If Output RO_SOLENOID = ON Then ON
    If Output StartFill = ON Then OFF




    RO_Solenoid
    Set OFF
    If Output StartFill = ON Then ON
    Defer 002:00 Then ON
    Defer 002:00 Then OFF

    Dump_Solenoid
    Set OFF
    If Output StartFill = ON Then ON
    If Output RO_SOLENOID = ON Then OFF

    RO_MembFlush
    Set OFF
    If Output Final_Flush = ON Then ON


    If I want the RO membrane flushed during water production for 30sec each hour would this work?Creat a Virtual outlet called FLUSHOSC with:

    OSC 000:00/000:30/059:30 THEN ON

    and add this line to my RO_MembFlush Solenoid

    If Outlet FlushOSC = ON Then ON


    ​Thanks!

  2. #2
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    I would suggest keeping it the way you have it, but have the membrane flush at the start of the cycle rather than periodically. I would do this process.

    First 2 minutes: flush and dump
    Next minute or two: dump no flush
    Final 2 minutes: flush and dump.

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  3. #3
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    Thanks Zombie....I assume this is better for membrane life and water production. So to accomplish this would this work (changes in bold):

    StartFill ( a Virtual outlet)
    If Lo_ATO OPEN Then ON
    If HI_ATO CLOSED Then OFF
    Defer 002:00 Then OFF

    FINAL_FLUSH (a Virtual outlet)
    Set OFF
    If Output RO_SOLENOID = ON Then ON
    If Output StartFill = ON Then OFF




    RO_Solenoid
    Set OFF
    If Output StartFill = ON Then ON
    Defer 004:00 Then ON
    Defer 002:00 Then OFF

    Dump_Solenoid
    Set OFF
    If Output StartFill = ON Then ON
    If Output RO_SOLENOID = ON Then OFF
    If Output FINAL FLUSH = ON Then ON

    RO_MembFlush
    Set OFF
    If Output StartFill=ON Then ON
    Defer 002:00 Then OFF
    If Output RODI= ON Then OFF

    If Output Final_Flush = ON Then ON

    Thanks!

  4. #4
    Frequent Contributor zombie's Avatar
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    You dont want the defer in the flush.

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    I guess I'm confused. How do I achieve the 2 minutes of dump without flush? From what I understand, when the Lo_ATO is open it will turn on my virtual outlet "StartFill" this in turn will turn on the RO Solenoid but it will wait 4 minutes before coming on. During that time both the Dump Solenoid and MembFlush Solenoid will be on dumping and flushing. When the 4 minutes is up, the RO Solenoid will open and the dump and flush solenoid will close. How do I achieve the flush solenoid closing while the dump stays open?

    sorry if I'm missing something obvious.

    Thanks again for your help.

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    I don't want to confuse the question, but, I don't think flushing the membrane every hour is a bad idea, especially if your system does run for multiple hours between "full tank" shutoffs and or you have above 150 TDS into the membrane. There is pressure during the whole cycle on your membrane(s) hopefully >60psi meaning that positive pressure is forcing TDS deeper into your membrane the longer the cycle runs. When you flush (remove the restrictor from the brine side via solenoid bypass is my assumption as opposed to true reverse) this allows the lightly packed debris to clear from the membrane. When you do this during operation (typically ~60minutes) you will see a decrease in brine (waste water) for the same volume of permeat (cleaned water), as well as overall longer membrane life. The above said if your runs are just over an hour and or TDS < 100 into the membrane, keep it simple. There are 24v auto restrictors available that do everything you are doing via APEX for about $25.00, which flush on start, flush 20 seconds every hour, with no programming. Of course you can do it via APEX the way you are, but you may want to consider putting a solenoid at the RO feed rather than at the delivery, in case your water pressure drops so you keep pressure on your membrane. If you want a diagram of such happy to send it or post it.

  7. #7
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    Thanks for the input. Those were my original thoughts. My system runs once every couple months and will generally run for about 18 hours before it fills my container and shuts off. My TDS is about 130- and my pressure is about 52psi. Since I have the apex all set up, I just wanted to get the programming correct. I'm still fairly new at this so I am not sure my original OSC program would work, and clearly I do not know what I am doing with the revised program based on Zombie's suggestions.
    Thanks again for making these suggestions.

  8. #8
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    NP Happy to help. You're right on track with the OSC you proposed, you just need to SET OFF as your FLUSHOSC virtual outlet or it would never turn off. This said, very simple test is to create your virtual outlet but don't reference it in your RO_MembFlush Solenoid outlet right away, but, check the log box. Then let your program run a few times as it normally would and check your fusion logs, this will show you when the v-outlet turns on and off. Assuming your code is correct, reference your new v-outlet in your RO_MembFlush Solenoid outlet as you plan. If not debug and or come back to the forum for some more help.

  9. #9
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    Thank you again. I actually wrote the FLUSHOSC in quickly a few minutes ago just before the top of the hour. It worked and then shut itself off. I see your suggestion for SET OFF but curious since my VO turned off without it after the 30 sec flush as depicted on the OSC command.

  10. #10
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    The OSC is supposed to turn off, but, I have seen anolomies (check my ATK post today about defer 180:00 On 3 x in 24 minutes) so especially with a device that can dump tons of water down the drain or worse, I like the positive statement. But... you are right, it is supposed to work without it.

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    Makes sense, thank you again.

  12. #12
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    Quote Originally Posted by cdavmd View Post
    I guess I'm confused. How do I achieve the 2 minutes of dump without flush? From what I understand, when the Lo_ATO is open it will turn on my virtual outlet "StartFill" this in turn will turn on the RO Solenoid but it will wait 4 minutes before coming on. During that time both the Dump Solenoid and MembFlush Solenoid will be on dumping and flushing. When the 4 minutes is up, the RO Solenoid will open and the dump and flush solenoid will close. How do I achieve the flush solenoid closing while the dump stays open?

    sorry if I'm missing something obvious.

    Thanks again for your help.
    You would need another VO that has a 2 min defer to stop the flush solenoid early.



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  13. #13
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    I see, I did not consider that- I thought it could just be adjusted by setting times on/off.

    One Last question in regards to the OSC command. When my system finished filling last night and closed the High_ATO, it proceeded to perform the FINAL FLUSH correctly and then shut down. However, it appears the OSC continued to open and close the Flush solenoid every subsequent hour. Would adding a line on the virtual outlet FLUSHOSC stating

    IF STARTFILL = OFF THEN OFF work to stop this behavior?

    Thanks again, this has been very helpful and educational.

  14. #14
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    Quote Originally Posted by cdavmd View Post
    I see, I did not consider that- I thought it could just be adjusted by setting times on/off.

    One Last question in regards to the OSC command. When my system finished filling last night and closed the High_ATO, it proceeded to perform the FINAL FLUSH correctly and then shut down. However, it appears the OSC continued to open and close the Flush solenoid every subsequent hour. Would adding a line on the virtual outlet FLUSHOSC stating

    IF STARTFILL = OFF THEN OFF work to stop this behavior?

    Thanks again, this has been very helpful and educational.
    Yes. Using startfill will make it so it only oscillates while filling.

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  15. #15
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    Thank you

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