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  • Surface finish on interior of vessels

    Hi everyone,

    I am in the process of purchasing brewery equipment, and am receiving some contradictory information between suppliers regarding the desired surface finish on the interior of vessels.

    I am particularly interested in what your thoughts are regarding fermenter vessels, because here a smoother internal finish would aid most with CIP.

    This is my current situation: One of our suppliers differentiates themselves by claiming all their equipment has internal mirror finish polishing. Other suppliers offer standard 2B finish with pickling and passivation, and when I asked whether they also do mirror finish 8K I received the following advice:
    “We advise to keep the acid water and passivation as it will do on 2B original plate and will also form a protective layer on the plate. The mirror type is very shiny and it is not good for the welders, and also could not do acid wash and passivation. But we can offer for free if you like.”
    I went back to the mirror-finish supplier, and shared the above with him, and this was his response:
    “Most other suppliers want to save costs, so they do passivation inside the tanks directly, and save polishing cost. And most other suppliers don't have the ability to do mirror polish inside. After passivation, the bad surface/welding pores and cracks will be covered but they are still there, you just cannot see them.
    After you receive the mirror polish tanks ,you have to do passivation simply again before you start to use them. Mirror Polish doesn't matter with the welding quality and does not affect the welding quality. On the contrary, it will test the welding quality. If the welding quality is not good, the welding pores and cracks will appear after polish.”
    So now I am confused: is mirror finish the way to go, or is it rather not advised? I’ve read it will help with cleaning, but the words of the first supplier above made me a little concerned. Does it really prevent a good passivation layer?

  • #2
    Hello Dieter,

    If a mirror finish will help, I am no practising brewer, I would choose electropolishing. It will most likely be quicker and cheaper and give a much better consistency of finish. Electropolishing in used in the pharmaceutical industry, reduces pumping down times in vacuum systems and used to polish medical items such as stents. It is also increasingly used in the automotive industry. Electropolished stainless steel looks like chrome.

    I hope all goes well.

    Best regards,
    Michael George.

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    • #3
      Polishing is not used by any of the jumbo brewers, and like their beers or not, they produce beer of highest microbiological standards. IMHO mirror polishing of internal surfaces is bullshit and a complete waste of time and money. I am convinced that in some cases that I have seen, the welding is such poor quality that they are using mirror finishing to hide the fact that the basic design and welding is poor quality.

      The key factors in hygiene lie in the rest of the design and finish - good welds, smooth weld finishes, pipework sizing and CIP and product flows being appropriate for brew size, use of appropriate CIP regimes and materials - the list goes on, but doesn't include mirror internal finishes. Many, perhaps most of the UK (and a number of European suppliers) 10 - 30 hl breweries I have seen use oversized pipework - a basic hygiene design flaw that polishing a few vessels will not overcome.
      dick

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      • #4
        Sorry, should have added

        Whichever finish you have, the vessels and pipework should be degreased and then passivated to ensure the oxide layer is complete. I have no idea if polishing makes passivation harder. Since it is a chemical reaction, I don't see why it should be any different to unpolished stainless, but suspect it might need to be done more rigorously. I don't know of a test that can be used for validating passivation
        dick

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        • #5
          Originally posted by dick murton View Post
          Polishing is not used by any of the jumbo brewers, and like their beers or not, they produce beer of highest microbiological standards. IMHO mirror polishing of internal surfaces is bullshit and a complete waste of time and money. I am convinced that in some cases that I have seen, the welding is such poor quality that they are using mirror finishing to hide the fact that the basic design and welding is poor quality.

          The key factors in hygiene lie in the rest of the design and finish - good welds, smooth weld finishes, pipework sizing and CIP and product flows being appropriate for brew size, use of appropriate CIP regimes and materials - the list goes on, but doesn't include mirror internal finishes. Many, perhaps most of the UK (and a number of European suppliers) 10 - 30 hl breweries I have seen use oversized pipework - a basic hygiene design flaw that polishing a few vessels will not overcome.
          Great, thanks for the info Michael and Dick!
          Seems mirror finish is probably not that important if it isn't used by the big brewers, so I will stick to the standard 2B finish.

          Good to know about the piping though - I imagine it has something to do with the piping being sized to constrict the flow enough during CIP to increase liquid velocity and thereby help "rub off" the organic material? Are there any general guidelines or an article I could read on how to size the piping correctly? I read another post of yours, Dick, where you mention something about product flow rate of 1.5 m/s, cleaning at 2 m/s, and then a wort inlet velocity of 3.5 m/s, although I don't quite get the difference between product flow rate and wort inlet velocity.

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          • #6
            Small pipework - less than 75 mm ID - clean at 2 metres / sec - so 25 mm = 3500 litres / hr. 40mm ID = 9000 litres / hr.

            the 3.5 metres / sec is specifically for wort inlet flow into a whirlpool

            1.5 metres / sec is the start of turbulent flow, and generally considered necessary for clean interfaces, but not so fast as to waste energy or damage the beer on transfer
            dick

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            • #7
              A few thoughts...

              Sprayballs are not designed to clean by impingement, but instead by the mechanical action of a cascade. So a gentle cascade over the entire surface to be cleaned is sufficient. More than that can actually decrease effectiveness by splattering the cleaner off the surface to be cleaned. I've found that polished surfaces are easier to clean than mill finishes, especially at the krauesen line. And all interior welds should be back-ground and polished to some degree at least. Just to note that Jumbo brewers also pasteurize all their product, so they don't require the same level of sanitation that small brewers might. Many don't even sanitize fermenters between batches as cleaning well removes most of their problems.
              Phillip Kelm--Palau Brewing Company Manager--

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              • #8
                Hi Phillip

                I'm intrigued. I have CIP training material from a number of jumbo brewers, including Fosters (as they then were), Coors and several UK brewing groups, mainly, I accept, before being swallowed up by the internationals, and by a few current chemical suppliers (all UK ops, I accept). None of them have ever mentioned not using sanitiser in FVs. There are several who mention not carrying out full cleans, just rinses of BBTs between the same product, or compatible product sequences (e.g. light beers followed by darker beers) for perhaps 5 fills, but that is all I am aware of. So as not to antagonise anyone, if you feel it more appropriate, I would be happy to receive a PM regarding the source of the info.

                But I agree that hot (65 C +) caustic cleaning will kill off most, but unfortunately occasionally not all bugs, and acid cleaning ditto - hence the use of combined acid detergent/sanitisers.

                Re pasteurisation, fair point about them generally using pasteurisation, but some people forget that if the beer has been infected earlier in the process and has resulted in off flavours then pasteurising is not going to eliminate those flavours - so it should only ever be seen as a shelf life extender, not a cure all for poor brewery process hygiene generally.

                Cheers
                dick

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                • #9
                  Hey Dick....

                  Tried to message you, but your inbox is full....
                  Phillip Kelm--Palau Brewing Company Manager--

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                  • #10
                    Hi Phillip

                    I've had a bit of a clear out. It should accept messages now.

                    Cheers
                    dick

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