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  • Odd Caustic Soda Residue Question

    Hello All,

    During our first caustic cleanings on brand new tanks, we ran into a residue issue with our Caustic Soda. To give some background, the tanks (brew house + FV’s) were manufactured by Specific Mechanical and they’re brand new. This was our first full CIP test with Caustic and we a have plenty of experience doing this process in work prior to having our own brewery.

    We followed the suggestion from our chemical supplier and made a 1% caustic solution with 50 centigrade H20. We performed CIP for 30 minutes and then rinsed with clean water. All via our CIP system.

    1. I’ve attached photos of the inside of our mash-tun after letting the 50 centigrade 1% caustic solution soak for a few hours (this was a test outside of our CIP test) and you can see the white residue left from the caustic soda.

    Residue Photos - https://drive.google.com/folderview?...zg&usp=sharing

    2. At first we thought it was from our own h20 – which is a relatively high alkalinity (8-8.5 pH) but we mixed the residue with water and tested the pH and it’s over 11 leading us to believe that it’s caustic residue
    3. I’ve attached the technical sheet for the caustic we used, it’s in Spanish so here are the highlights

    Technical Sheet - Caustic - https://drive.google.com/file/d/0B7B...ew?usp=sharing

    a. General Use Description - Product is specifically designed for effectively cleaning all organic material in CIP, UHT equipment, piping, tanks, and general equipment.
    b. Ingredients: Sodium Hydroxide, CAS # 1310-72-2, %(m/m) 30-50, OSH (PEL) ppm 2mg/m3
    c. Specific Weight – 1.430-1.530
    d. pH 13.00-14.00

    Our thoughts:
    • 50 centigrade h20 is too hot – perhaps try with ambient temp h20
    • Bad caustic soda – this caustic seems very viscous compared with caustics that we’ve had prior experience with in the USA. It seems to be 2x-3x more difficult to wash off your hands.
    • Too much calcium in the h20

    Any help or thoughts on folks who have run into this problem would be greatly appreciated!!

    Thanks!

  • #2
    Not able to read Spanish, but this appears to be a safety data sheet, which doesn't give any indication of the type of formulation, merely mentioning the major active ingredient - NaOH. My suspicion is that this is not formulated with appropriate types of, and levels of wetting agents and rinsing agents etc. suitable for your water.

    Your water has high alkalinity, suggesting high(ish) levels calcium carbonate / bicarbonate - but I assume you have an accurate mineral analysis of this. The carbonates / bicarbonates ideally need to be removed before using for CIP by passing through an RO plant, water softener or similar, or possibly simply neutralised carefully with mineral acid such as sulphuric (NOT hydrochloric) to remove the carbonate and bicarbonate.

    If you don't have this capability, and alternative to go to the supplier and get them to formulate the additives specifically for your water.

    Since high pH / carbonate / bicarbonate water is not ideal for brewing either, providing this is the only thing wrong with your water, I suggest that you acid treat all the water before use for anything, accepting that you are likely to have calcium sulphate precipitated into the holding / treatment tank, so will have to dig out, clean out on a regular basis. Providing your water source is consistent, the mineral content should be fairly consistent, so once you know that x ml H2SO4 (food grade) will reduce the pH of y litres of raw water to pH 7, or possibly even 6.9, then you should be able to top up a tank, and add an appropriate volume of acid, mix thoroughly and check after 10 minutes or so.

    Pre-treating the water will normally be cheaper than paying silly money for additional chemicals to be added to your cleaning materials.

    If you don't pre-treat the water to remove bicarbonate, and you use hot rinse water, or even apply cold rinse water to hot brewing plant, then bicarbonate evolves CO2, leaving the carbonate form, which then precipitates - leaving the white scale you have there. I have seen scale nearly 1 cm thick on a couple of tanks at a brewery where they tried to cut costs by using non formulated (raw) caustic.

    You could follow the post caustic rinse with an acid rinse, to remove any scale build up, but you still have to rinse off with high carbonate / bicarbonate water - so I recommend treating all the brewery water first, then with a decently formulated detergent, you should only rarely need to acid wash.
    dick

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    • #3
      +1 on the not properly formulated cleaning agent.
      Raw sodium hydroxide tends to absorb CO2 from the air and forms carbonates and bicarbonates, properly formulated cleaners have additives that reduce this issue.
      One way to work around this issue is to lengthen your post caustic rinse.
      If you recirculated at 50 C your tank will be hot, so if you do a short rinse the hot surface of the tank will speed up the drying of caustic residue making the problem worse. A long rinse will reduce the problem but use more water. Also check your CIP balls to see if you have good coverage.


      Sent from my iPhone using Tapatalk

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      • #4
        Thank you much for the replies.

        We are now working on sourcing new vendors that have a better cleaning formulation - I'll report on new tries. I've shared the "wetting" and "rinsing" agent observation to them.

        Our Water Profile is:

        Ca 50ppm
        Mg 14ppm
        CaCo3 (Hardness) 170ppm
        CaCo3 (Alk) 350

        My understanding of the above is very high temporary hardness and a boat load of bicarbonate.

        Dick - I am planning to acidify with Lactic, thoughts? We have a holding tank (underground - below room temp) that feeds our HLT and brewhouse. The water line that comes into this holding tank has a dosing pump connected to it.

        forrestmz3005 - definitely the high temp were allowing the caustic solution dry up quicker and burst rinsing wasn't helping; however, we then tried to rinse with a significant amount of water, but even by the time we changed the hose connections to rinse with water, the solution had dried (because of temperature) and we start to see residue.

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        • #5
          I have limited experience using lactic acid, but don't see why it shouldn't wok, though if I was going to brew bitters, pale ales I would be tempted to use food grade sulphuric - over here at least it is cheaper and gives good, repeatable results. I know some people use Phosphoric with good results instead of sulphuric with less risk of sulphury flavours in the final beer.
          dick

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          • #6
            Caustic soda is a poor detergent.

            A formulated caustic detergent will contain caustic soda, surface tension reducing agents, foam inhibitors and a chelating agent (EDTA is the best one. Soaks up these things and beerstone like nothing) to increase the cleaning ability.

            Either you buy a formulated caustic with EDTA or do a run with acid afterwards.

            Comment


            • #7
              We get that a little bit. Rinsing it off prior to drying really does help tremendously. Immediately after you turn off your CIP pump spray the area off with a washdown hose. I would also check and see if your CIP pump is rated high enough for the system CIP loop you are running. Looks like the spray balls are not hitting the manway area very well and they is causing to to dry before rinsing. A rotating sprayball might help keep the area wet until it can be rinsed.
              Joel Halbleib
              Partner / Zymurgist
              Hive and Barrel Meadery
              6302 Old La Grange Rd
              Crestwood, KY
              www.hiveandbarrel.com

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              • #8
                Wanted to let everyone know how it has all played out.

                We were able to treat the water with some acid, reducing the scale that was forming; however the problem persisted in a smaller manner. We then tried a different provider of chemicals. The new formulated caustic detergent contained caustic soda, and many more (as the other one lacked those) surface tension reducing agents and foam inhibitors. We see much better results with this. Pretty much no scale after rinsing.


                However, we havent been able to remove some stubborn boot marks (I'm guessing from the welders) or just black shoe marks that seem to be backed into the stainless (see pics below).

                We've ran a formulated caustic detergent, jumped in the tank and scrubbed it with the green scotch-brites using a citric-based orange peel degreaser and then ran another caustic cycle. Thoughts? These tanks were built by Specific Mechanical and brought to us new.

                Click image for larger version

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                We've ran a formulated caustic detergent, jumped in the tank and scrubbed it with the green scotch-brites using a citric-based orange peel degreaser and then ran another caustic cycle. Thoughts?

                Comment


                • #9
                  What Is the final finish on the tanks? From the pictures I see some scratching. Are they polished?
                  The reason I am asking, is that all SS needs a passivation treatment to form an oxide protective layer on the stainless. This passivation also helps with cleaning a lot of residues created during fabrication. Passivation is usually performed with a nitric acid based cleaner recirculated for some time. There is extensive info on passivating Stainless steel online also ASTM A-380 spec will give you a guideline on passivating and cleaning your tanks.


                  Sent from my iPhone using Tapatalk

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                  • #10
                    I'm no stainless expert, but I believe only the internal welds have been really polished (shinny areas).

                    We did indeed try to passivate this tank with Nitric Acid. Used a solution that contained concentration of 40% Nitric Acid @ 18 liters and mixed it with 60 liters of water then recirculated for 45 min. After rinsing with water and running one more caustic cycle (after the passivation) and rinsing again, those are the pictures you see.

                    We see 2 things:
                    1. Foot prints/shoe prints/black "grease" streaks
                    2. A shinny silver metallic residue when whipping tank interior with a damp rag


                    Click image for larger version

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                    After spending all day talking to people on the phone - equipment manufactures, chemical providers and other brewers. Here is what we found:

                    Asian made tanks (even those "QAd" by North American mfg) tend to have this metallic residue on the inside of the tank. Seems to be a direct issue by not tickling (some sort of cleaning of stainless) the tank adequately before shipping.
                    There is no 1 way to fix this. Only options to try. A representative at Loeffler, who was the most knowledgable person we spoke to, (and we recommend you do too if running into somthing similar to that) gave us different options to try. We will report back.

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                    • #11
                      Looks like you might have "mill scale" issues. Here is something my chemical supplier wrote to me about it because he wanted to make sure my equipment didn't have any present before cleaning and passivation:

                      After a conversation with another of our sales representatives this week, I wanted to reach out to you about a problem that he has recently seen in some of his new brewery customers. He explained that he has been seeing “mill scale” in new stainless kettles/tanks/equipment more frequently as of late. This is a by-product of the production of the stainless steel, not the equipment manufacturer. He described this material as a gray or chromium metallic dust that is present on the surface of the stainless and is extremely tough to remove. He explained that caustic won’t touch it and normal acid passivation is the same, it must be removed prior to acid passivation. If you have it present you should be able to see it with a bright flashlight or by wiping a white cloth across the surface of the stainless. It is likely not a problem for you; however, I wanted to pass along the info, as I know you have all new equipment. If by chance you find that you do have an issue with “mill scale,” let me know and I will get you a procedure to remove it.

                      Send me a PM if you'd like me to put you in touch with him. The company he represents has been great to work with.

                      Cheers,
                      --
                      Don
                      Last edited by idylldon; 09-10-2016, 05:37 PM.

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                      • #12
                        My experience of this dust is that the kit needs to be degreased / "de-dusted" and unfortunately, simply recirculating hot detergent didn't work, so I had to resort to getting inside and manually scrubbing with nylon brushes and scotchbrite pads etc, with strong degreasant (we used a commercial kitchen type - no idea what sort as this was in France a couple of years ago) After a couple of goes, I then recirculated 5 % formulated caustic at 80 deg C for an hour, rinsed off - grease swab tested and then passivated with 5% nitric at 60 C for over an hour. This was Chinese kit, and I hate to think whether we managed to degrease all the pipework (also Chinese supplied and installed) before using it, but we didn't have any head retention or flavour problems, so I guess it was adequate.
                        dick

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