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Thread: New BBT with weld burns and strange film after first CIP

  1. #1
    Join Date
    Nov 2013
    Location
    Antigua, Guatemala
    Posts
    27

    New BBT with weld burns and strange film after first CIP

    I've been installing and bringing online (5) 30 bbl FV and (2) 30 bbl BBT, all brand new from China. I began the CIP of the final BBT on Monday and ran into some real issues. All the other tanks cleaned up great and are in use. The manufacturer swears they are passivated so I used a 2% caustic (sodium hydroxide) at 140-150 F for 1 hour followed by 2% acid (phosphoric) at 100 F for 1 hour. I've had trouble finding Nitric to do a full "re" passivation but I will follow up with that soon (even if we have to import).


    My problem is with the last BBT. After the caustic clean a lot of weld burns showed up including around jackets, dimples, etc, that really worry me. Lots of dimple spots are burnt, some much worse than others. Also there is this very cloudy film over the entire tank interior, especially prevalent on the polished band areas. It looks kinda like fish scales, not a solid layer of film but variegated, sorry for the shitty description. This really has me perplexed. Also there's one big area that looks like a birthmark for lack of better words where it looks like any kind of passivated layer has been stripped right off. None of this was readily apparent upon initial visual inspection of the tank. It all really showed up strongly after the caustic.


    I've tried to CIP again, I've tried to scrub certain areas by hand with caustic, PBW, acid, and nothing seems to have any effect. None of the other tanks had any of these problems, no weld burns, no film, nothing.


    Anyone seen this type of thing before? Ideas?
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  2. #2
    Join Date
    Jun 2011
    Location
    Richmond, VA.
    Posts
    425
    it might be from doing the caustic first then the acid. i have heard to pacifie new tank you should do an acid first followed by a caustic. try taking a scrubby with an acid solution to remove the rust and the try another acid cip.

  3. #3
    Join Date
    Feb 2012
    Location
    Chicago, IL
    Posts
    88
    Having worked for a Chinese supplier and oversaw the production of our tanks within our Chinese factory, I can most likely assure you the tanks have been passivated. The problem is, these weld marks indicate that the welder was too hot and burned through the material. These welds will need to be acid cleaned with a pickling gel and/or ground flush with the tank. No CIP solution will clean these marks. In addition, there is going to be sugar'd material that will harbor bacteria. You need a welder to get into these tanks and clean them up. I'm sorry for the hassle but this is why Chinese tanks can be a nightmare.

    James

  4. #4
    Join Date
    Nov 2013
    Location
    Antigua, Guatemala
    Posts
    27
    Quote Originally Posted by NHBrewer23 View Post
    there is going to be sugar'd material that will harbor bacteria.
    Thanks James! Sounds like climbing in there with pickling gel might be the first step. I found some from another chemical provider here in Guate, so....in I go.

    Can you explain the "sugar'd material"? Is this what may be showing up on all the polished areas? This stuff really has me scratching my head?!

  5. #5
    Join Date
    Aug 2013
    Location
    China
    Posts
    789
    Yes,these welding marks indicated that the welder was too hot and burned through the stainless steel plates.
    You can polish these places slightly,then passivate these places again.
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