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Thread: Differential Tank Cooling

  1. #1
    Join Date
    Dec 2014
    Location
    Morgantown, WV
    Posts
    11

    Differential Tank Cooling

    Hello All,

    So we have four 14 bbl fermentors, and two 14 bbl brite tanks, all in a row, with the first tank receiving the first drop from the chiller but with it's return being the last in line to return. Our loop has been working fine for the past 4 years. We've recently been having problems with the first and last tank. The first tank is having trouble coming down to temperature after we set up a gradient crash, and the last tank is having trouble maintaining temperature of 38F (creeps up to 43F, glycol valve says it's open 100%). All tanks in between are fine with temperature regulation.

    Just wondering, before I dump a bunch of money, time, and mess in testing the solenoid valves on these tanks, is there something happening here or a "best method" of diagnosing this problem without a glycol mess on my hands? I have ball valves at each tank, so switching out the solenoids wouldn't be too messy. I would just hate to replace the solenoid valves only to have that do nothing. Is there a life-expectancy on solenoid valves? Any way to test them?

    Thanks for any input you may have.

    Cheers,
    Bill

  2. #2
    Join Date
    Nov 2009
    Location
    Moab, Utah
    Posts
    602

    Specifics

    Quote Originally Posted by Chestnut_Bill View Post
    Hello All,

    So we have four 14 bbl fermentors, and two 14 bbl brite tanks, all in a row, with the first tank receiving the first drop from the chiller but with it's return being the last in line to return. Our loop has been working fine for the past 4 years. We've recently been having problems with the first and last tank. The first tank is having trouble coming down to temperature after we set up a gradient crash, and the last tank is having trouble maintaining temperature of 38F (creeps up to 43F, glycol valve says it's open 100%). All tanks in between are fine with temperature regulation.

    Just wondering, before I dump a bunch of money, time, and mess in testing the solenoid valves on these tanks, is there something happening here or a "best method" of diagnosing this problem without a glycol mess on my hands? I have ball valves at each tank, so switching out the solenoids wouldn't be too messy. I would just hate to replace the solenoid valves only to have that do nothing. Is there a life-expectancy on solenoid valves? Any way to test them?

    Thanks for any input you may have.

    Cheers,
    Bill
    Provide the following:
    Glycol Supply Temp in Degrees F
    Glycol Supply Header pressure in PSIG
    Line size
    Photos of control valves, tank drops in and out, loop pump, and chiller are helpful
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  3. #3
    Join Date
    Jan 2003
    Location
    Palau
    Posts
    2,029

    Not too sure about this....

    If you are using ball valves with solenoid pilots, then it is very easy to see whether the ball valves respond to solenoid open or closed. My first guess is that perhaps you have air in the system that might need to be bled. I assume that all tanks are fed glycol supply to the bottom of the jacket? Otherwise, ball valves are very robust and will not clog like typical direct solenoid valve applications. Pressure gauge on glycol pump outlet header helps to diagnose problems. Cannot think of a reason why this would be too hard to troubleshoot.
    Phillip Kelm--Palau Brewing Company Manager--

  4. #4
    Join Date
    Dec 2014
    Location
    Morgantown, WV
    Posts
    11
    The supply temp is 28F. The supply PSI is 20. The trunk is 1.5 inches sch80 PVC and the copper drops to the tanks are 1/2 inch. Each tank has two cooling zones, one in the cone and one for the upper part of the tank. These have run fine for four years now, and we're just now having issues.

    While watching the supply pressure gauge, there is a a drop of about 4 PSI for all the fermentors when the solenoids are manually open. For our first BBT, the drop is only 1-2 PSI and then it immediately climbs back up to 20PSI. An even smaller drop in PSI (0.5-1) when the second BBT (problematic BBT) solenoid valves are open.

  5. #5
    Join Date
    Nov 2009
    Location
    Moab, Utah
    Posts
    602

    A few things to look at

    Quote Originally Posted by Chestnut_Bill View Post
    The supply temp is 28F. The supply PSI is 20. The trunk is 1.5 inches sch80 PVC and the copper drops to the tanks are 1/2 inch. Each tank has two cooling zones, one in the cone and one for the upper part of the tank. These have run fine for four years now, and we're just now having issues.

    While watching the supply pressure gauge, there is a a drop of about 4 PSI for all the fermentors when the solenoids are manually open. For our first BBT, the drop is only 1-2 PSI and then it immediately climbs back up to 20PSI. An even smaller drop in PSI (0.5-1) when the second BBT (problematic BBT) solenoid valves are open.
    First thing, open loop brewery chillers that have the glycol well at atmospheric should not " air lock."
    This does not mean it cannot happen if certain dynamics are in strange states. In the Chill water world we generally have devices we can read pressure drop across HX.
    Your tanks should be piped in and out of the header with flexible hose that can be easily disconnected, and having isolation valves close to the supply and return header.
    Disconnect your return hose on the offending tank and have some 5 gal buckets and a stop watch ready so you can estimate GPM. Compare that to the one that is working right.
    You can also read Delta T, if you have the right gear.
    Return the glycol to the central well.
    On PVC piping systems you really need 50 mesh Wye or TEE strainers ahead of every servo. Also there are a major lot of high priced solenoid valves being sold at large that are not that reliable. Its possible to get foreign objects stuck at the solenoid inlet or in the valve body that can restrict flow. Most decent valves can be easily disassembled and put back together quickly, but you are advised to have the correct repair kit on hand. If the system performed well in the past and the load has not been added to, and the readings all around are the same your situation is to find out " what has changed." Its important to never induce certain manner of thermal shock in these kinds of vessels. This can do serious damage.

    Sincerely

    Star
    Last edited by Starcat; 07-18-2019 at 01:49 PM.
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  6. #6
    Join Date
    Jul 2005
    Location
    Auburn, WA / Winston Salem, NC
    Posts
    277
    To echo the direction outlined above. A few items I'd look at:

    entrapped air- was the system opened recently for repair? Can you view the glycol solution in the reservoir, is it cloudy or clear?

    plugged filter/strainer- are there strainers or filters in the glycol loop that could be plugged.

    Pressure or manual Bypass- if there is a bypass valve, either pressure or manual, make certain it isn't providing the glycol with a path of least resistance- around your vessels.


    Hope this helps- good luck with getting this resolved.

    Jim
    Jim@prorefrigeration.com
    Pro Chiller Systems

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