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  • Heat Exchanger Passivation

    Are you passivating your HEX in the same manner as your stainless-steel vessels? If so, are you running o2 through the hex to purge all moisture out after the cycle and encourage the reformation of the oxide layer?

  • #2
    You don't need to expose to air. It doesn't work as well as (my favorite) hot 5% nitric acid or tartaric acid. Discussions about passivation on this site using citric, tartaricm nitric acids. Look up the ASME protocols. But don't waste time trying to use air.
    dick

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    • #3
      I just let mine drip dry when the cycle is done. After rinsing out obviously. I don't bother to blow air through it, and haven't seen any issues as of yet.

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      • #4
        I have not made a habit of periodic passivation of heat exchangers. Nor tanks, for that matter. What benefit is there to a periodic passivation? My tanks are spotless without messing with expense of strong chemicals, nor the water and labor it takes. Why do folks do this?
        Phillip Kelm--Palau Brewing Company Manager--

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        • #5
          Originally posted by gitchegumee View Post
          I have not made a habit of periodic passivation of heat exchangers. Nor tanks, for that matter. What benefit is there to a periodic passivation? My tanks are spotless without messing with expense of strong chemicals, nor the water and labor it takes. Why do folks do this?
          If you're lucky like me...you inherited a brewery where someone had previous attempted to clean the inside of the vessels with some sort of scrub pad, that has left gouges and/or scrapes on the tank wall. Passivating semi regularly(I do my tanks every third cleaning cycle) will help keep them from rusting out on you. If your vessels are still in more or less pristine condition, you shouldn't really need to. The odd descaling maybe, but those concentrations are vastly different from my limited experience.

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          • #6
            After an initial passivation, I don't think you need periodic maintenance to prevent rusting. That indicates inferior steel to me. I haven't seen tanks that require so much attention. Wash tanks immediately after use and keep them spotless. IMO, too much passivating going on out there!
            Phillip Kelm--Palau Brewing Company Manager--

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            • #7
              I would say there is not too much passivation going on. I am not saying this because I am working for a chemical supplier. I have seen many breweries and a lot of equipment which has not been properly maintained. One piece which is often neglected is the HLT. Every stainless-steel surface with product contact and which requires cleaning and sanitation should be regularly passivated. The chromium oxide layer protects the stainless steel from harsh and corrosive products and chemicals. The chromium oxide layer is only a few molecules thick and needs regularly to be "re-built". What is the best passivation procedure? I recommend the AMSE version. I fully understand the problems of a strong nitric acid, but it provides the most solid passivation layer. Using citric acid, the passivation of the chromium depends more on the available O2. As an example: a 1,000 bbl tank, treated with citric acid, requires about two weeks to from the chromium oxide layer. In addition, a blower needs to "refresh" the air in the tank to keep the O2 level at approx. 21 %.
              The passivation layer also smoothens the surface in case of small scratches. The smoother surface also helps to reduce the adhesion of fouling to the surface and reduces the cleaning effort.
              Zee Loeffler
              888-484-6248 (US & Canada only)
              www.loefflerchemical.com
              Oliver.meinhold@vincitgroup.com

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              • #8
                Hey Oliver! I'll bet you do see the worst of misused brewery tanks. That stands to reason. Certainly a brewery needs proper maintenance! I don't think passivation as a recurrent cure for poor maintenance or poor CIP procedures is good SOP. I can keep my tanks shiny and free from stone or other contamination just fine with proper CIP SOP. Rust in tanks?! Never. I can't see how that could happen with good metal passivated at factory. I disassemble heat exchangers once yearly for visual inspection. Never had to re-passivate. I don't think that passivation is required for stainless that has been properly cared for. Certainly not every 3 uses! I won't re-passivate if I don't see a need, or "just in case it needs it". And just to clarify, manufacturers of tanks polish the interiors with the same 3M scrubbie materials that many brewers avoid. They do however take care to observe grain direction. And passivate after the tank has been polished. Once. All that said, my CIP SOP includes warm acid wash after warm caustic and before sanitizer. That acid wash is usually nitric/phosphoric based. Perhaps this helps "refresh" the oxide layer.
                Phillip Kelm--Palau Brewing Company Manager--

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                • #9
                  Originally posted by gitchegumee View Post
                  After an initial passivation, I don't think you need periodic maintenance to prevent rusting. That indicates inferior steel to me. I haven't seen tanks that require so much attention. Wash tanks immediately after use and keep them spotless. IMO, too much passivating going on out there!
                  As I mentioned, if your tanks are in good condition, you shouldn't need regular passivation. The people who owned the brewery before I got here, had at some point used aggressive scrubbing techniques and/or chemicals, leaving some nasty scratches and gouges in all my vessels. That's the biggest reason I personally need to passivate often. We were getting a fair amount of nickel and iron leaching into our products, which dropped shelf life massively. When I took over the first thing I did was clean and passivate every vessel, and our iron/nickel levels dropped by almost 70%. Like most things, it will vary dramatically on your equipment and processes. For us, we still have industry standard stainless, it was just beat to sh*t by previous users and now requires constant love to keep the beer happy.

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                  • #10
                    There must be a standard or a metric/threshold by which to judge when passivation is necessary. What do I look for & how do I measure when passivation is necessary in brewery vessels? I've used bright lights to look for faint bronze sheen of calcium oxalate as evidence that the tank needs more frequent acid wash. How does lack of passivation manifest? Pickup of metals in beer? Thanks in advance!
                    Phillip Kelm--Palau Brewing Company Manager--

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                    • Icedpyre
                      Icedpyre commented
                      Editing a comment
                      In theory, it should only need to be done after machining at the factory, or if something has abraded the protective layer that passivating provides. I couldn't personally say if there's any metric as to time or visual inspection that would indicate it needs passivating. I just know that the people who owned this brewery before we bought it, beat the bejeezus out of the vessel interiors, so I do it every few cleaning cycles out of necessity. It drives my chemical costs up, but they were having metals show up in lab tests until I started doing it, so I'm going to continue running things that way.

                      I would personally think that if you aren't having any stability issues with shelf life, you probably don't need to worry TOO much about passivating. Just make sure you regularly run caustic and remove beer stone with acid of choice.
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