The PETROBRAS experience obtained during the construction and maintenance of Bolivia-Brasil and several other gas pipelines has consolidated an option for high performance corrosion coatings, as polyethylene and polypropylene three-layer coatings, knowing that the correct surface preparation is the key to ensure its quality. This paper presents the evolution of the Company's quality control practices for surface preparation, specially comparing the results obtained by using different roughness meters and the correspondent known roughness parameters. 1) When the roughness of a blasted surface has to be specified to receive some kind of coating, to provide the best anchor pattern as possible, it is mandatory to precisely define the value and the parameter that will be needed. So that, when an electronic linear tester, for instance, should be used, it will be certainly possible to set the proper parameter. 2) Press-O-Film (POF) is still one of the most widely employed roughness measurement method for steel pipes on a coating plant. We can affirm that, if the last blast equipment used grit, POF values will have the best correlation to Rz DIN parameter than to any one analyzed in this paper. 3) Likewise, if only shot were used, POF values will present a best correlation to Ry parameter (maximum profile valley depth). 4) The inverse of Sm parameter - mean spacing of profile irregularities - indicates a peak density parameter. Shot blasted steel surfaces presented the highest Sm values, consequently the lowest peak density. That can be undesirable for a good coating adhesion. On the other hand, if the last blast equipment applies steel grit, peak density will be closer to the desired value. 5) A single equipment steel blast system having a mix of 50-50 S230 shot and G25 grit results on surfaces with lower roughness and peak density values than if a double blast system is used, the first with shot and the second having a majority of grit (G25).


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    Title :

    Measuring roughness of blasted steel pipe surfaces: a case study


    Contributors:
    Koebsch, A. (author) / Campos, P.H.L. (author) / Portesan, G. (author) / Gandur, M. (author) / Taves, J.M.V. (author)


    Publication date :

    2005


    Size :

    15 Seiten, 26 Bilder, 2 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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