Damaged coating inside concrete water tank  


Posting by Alex on 24 Aug 2008 at 14:54:33.

Hello:

We have a problem with liners/coating on the concrete tanks filled with demineralized water in a nuclear power plant. Liners are:
- epoxy based and/or
- polyurethane based (both 1-2 mm thick)

Liner is separating ('blistering') from the concrete substrate. Do you have any experience or explanation? Can your chemical - physical simulation programme (the CheFEM tool) for coating assessment deal with this sort of industrial application in a proper manner? I really prefer a maintenance free and fit-for-our-purpose coating to concrete tank solution since the residual lifetime of the current solutions is less than a year or maybe even less than a month...

Thanks,
Alex

p.s. I am little resistant to another set of laboratory tests or some sort of quote for an inspection survey.


          follow up posts
    On 06 Dec 2008 at 05:08:00 Dilip posts:
    I am facing the same problem. We are supposed to store DM water at 60 Deg. C in a RCC Tank. Two of supplier has proposed (1) PU coating (2) Polypropylene Coating. I will be thankful to u if u can guide me which suits best for application in Concrete tank.
    [responses: 1]
      On 08 Dec 2008 at 09:46:53 Composite Agency posts:
      Dear All:

      Probably the best option is an epoxy (phenolic) based liner, with the structural strength of a "tank in tank" solution, and sufficient cast epoxy on the inside and outside of the tank (the glass
      fibres must be protected well from the water, otherwise capillary uptake and subsequent fibre-epoxy degradation may come into play, for exact laminate definition also the outside environment of the tank is of importance; atmospheric or moisture dry circumstances). Reason is that PP will not adhere to concrete and has insufficient structural strength, PU will have a better adhesion but swells to much under the load of water (and some of them get decomposed by water).

      Please contact us for quantitative analysis regarding blister formation driven by water in combination with leaching from the concrete, moisture diffusion and corrosion rates, epoxy fibre laminate definition / required structural strength (using CheFEM Simulation).

      Regards
      Composite Agency


      [responses: 0]

    On 13 Nov 2008 at 17:23:08 Michael Lee posts:
    Alex,

    A coating based on hybrid technology resists up to 250 degrees Celsius. Contact me for further information:

    DuraPol Limited
    E-mail: info@durapol.co.uk
    Tel: +44 1274 484810
    Web site: www.durapol.co.uk

    Regards,

    Michael
    [responses: 2]

      On 03 Dec 2008 at 23:11:36 Alex posts:
      Michael, thanks for the helpful website reference. I am mainly interested in epoxy tank coating / liner. Water temperature varies from 25 to 100 degrees Celsius. Is the adhesion between the epoxy coating and the concrete tank normally an issue?

      Regards,
      Alex
      [responses: 1]
        On 03 Dec 2008 at 23:49:13 Michael Lee posts:
        Alex,

        Demineralised water is much aggressive and will permeate coatings compared with potable or sea water. Blistering will be rapid if the epoxy or polyurethane coating is not designed for immersion service.

        From past experience this type of situation will call for a composite coating system consisting of sealer/primer, glass fabric reinforcement and a temperature/permeation resistant top coat. The exact details can be specified once the following questions are answered:

        Is there impurities in the water?
        Does the temperature remain constant or vary in each tank?
        What was the condition of the concrete prior to it being coated?
        How old was the concrete before it was coated?
        How thick is the concrete tank wall?
        What is the temperature on the outside of the tank?
        Will the temperature of the water be in the range 25-80 degrees Celsius prior to entering the tank?
        If the epoxy / polyurethane has blistered has this had an affect on the condition of the concrete?

        Regards,

        Michael

        DuraPol Limited
        E-mail: info@durapol.co.uk
        Tel: +44 1274 484810
        Web site: www.durapol.co.uk

        [responses: 0]


    On 17 Nov 2008 at 15:03:44 Charles Lamb posts:
    Dear Alex:

    Further to the remark of Michael, I am curious whether - at an ambient temperature - a plastic, say epoxy, is required with or without glass fibres? I read that frp with glass flakes - although that the glass flakes add to the mechanical properties - are no good for the water, acid, alkaline (as is probably the case in the nuclear tank) FRP diffusion and chemical resistance. And what about FRP containing Chopped Strand Mat (CSM) or FRP with Woven Roving?

    What is the best FRP material avialable for these sorts of applications from the viewpoint of mechanical, corrosion resistance and permeation properties? Please help me since the available FRP corrosion and chemical resistance guides are not clear with this regards.

    Sincerely,
    Charles Lamb

    [responses: 0]



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