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Thread: Packing Heat Exchanger With PAA - Recommendations

  1. #1
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    Jun 2019
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    Packing Heat Exchanger With PAA - Recommendations

    My SOP for the brewhouse HX is to run a caustic cycle after brewing and then run a short PAA cycle (~0.3% solution) and leave packed until next use. Our capacity allows for longer downtime now and I'm wondering if I need to be doing more between brews. Any ideas on how long PAA is supposedly viable if packed in the HX? Should I be worried about my HX gaskets degrading?
    Last edited by Peters; 01-09-2020 at 10:56 AM.

  2. #2
    Join Date
    Oct 2013
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    Stuart, FL
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    Quote Originally Posted by Peters View Post
    My SOP for the brewhouse HX is to run a caustic cycle after brewing and then run a short PAA cycle (~0.3% solution) and leave packed until next use. Our capacity allows for longer downtime now and I'm wondering if I need to be doing more between brews. Any ideas on how long PAA is supposedly viable if packed in the HX? Should I be worried about my HX gaskets degrading?
    First, I would always recommend you contact the HX manufacturer for their best practices recommendation. Generally, it is recommended to run your CIP solution in the reverse direction of normal flow at 150% of normal operating flow rates. I often run my solution in both directions for a period of time, simply because I can easily. The typical cleaning solution range might be around 0.5-2% by volume of liquid caustic product depending on temperature and efficacy. Looking for a pH of 12+ at the end of cycle. Flush until pH neutral. Occasionally I will pack my HX with caustic for a 12hr period as a "deep soak".

    Packing with PAA is my preferred method, and I have not seen it cause issues over prolonged periods on EPDM gaskets. You can verify the chemical compatibility of your gasket material with PAA on many independent websites. You will find it has a B or better rating for peracetic acid and hydrogen peroxide independently at the strength you will find most suppliers offering. By the time you dilute that 0.3% PAA (with the 24% H2O2 it likely contains included) to the proper sanitation strength, you will find that you are well below the threshold of concern for compatibility. Your strength for sanitizing should probably be a minimum of about 150ppm depending on the exact product you are using. I like LaMotte strips and just check for 180ppm+

    The PAA is extremely effective at killing over prolonged periods (even at very low concentrations) and that is why I prefer to pack myself. I have seen studies showing that while degradation of PAA can occur quite quickly, the addition of hydrogen peroxide helps improve stability drastically (this is part of the reason they blend the H2O2 and PAA). In documented literature I have somewhere, I have seen effective capacity beyond one month in normal circumstances. With that said, I always re-run a sani loop if my equipment has been sitting more than a couple days, and replace my soak and sprayers every week or so.

    The best objective way to verify your results is through ATP or environmental swab and incubation. You should also run a de-mineralization cycle periodically. Usually a nitric/phos blend will be the best option, but this should never be left packed for long times. I tend to run one about every trimester or so.

  3. #3
    Join Date
    Jun 2019
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    East Coast
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    Very useful, thanks for the info UnFermentable

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