Preparation of material

 cesta pitanja

  • Material to be galvanized should be clean, without any trace of insoluble matters such as oil, grease, paint, lacquer, whitewash, welding residues, color pencil marks, etc.
  • Welds must be clean and compact without slag, drops etc.
  • Required technical openings must be drilled
  • No paint is allowed on items.

HOW TO PREPARE MATERIAL FOR GALVANIZING

Items are galvanized in accordance with ISO 1461 which defines thickness of zinc coating in a form of a table.

Items Minimum local thickness of an item coating [µm ] Minimum local thickness of an item coating [µm ]
Steel > 6mm 70 85
Steel >3mm≤6mm  55  70
Steel ≥1,5,mm≤3mm  45 55
Steel <1,5,mm  35 45
Castings ≥6mm 70  80
Castings <6mm  60 70
  •  Table 1 Minimum and average zinc coating thickness over items
Steel pipes [mm] The smallest Ø of opening  [mm]
Round      Square   Rectangular Openings in both ends must be immediately next to a weld site
                15             15             20x10                    6
                20             20             30x15                   8
                30             30             40x20                    10
                40             40             50x30                    12
                50             50             60x40                    16
                60             60             80x40                    20
                80             80             100x60                    20
                100           100           120x80                    25
                120           120           160x80                    25
                160           160           200x120                    32
                200           200           260x140                    32
    • Table 2 Recommended smallest dimensions of openings for deaeration / bleeding according to EN 1461

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  • Figure: Incorrectly executed

  • Figure 1 Examples of openings for deaeration / bleeding in closed pipes

  • It can be seen that openings and holes are made next to weld edges, i.e. next to closed space edges.
  • priprema 002aFigure 2 Closed pipe structures with square cross-section

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  • Figure 3 a; b: Closed pipe structures with round cross-section

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  • Figure 4 a, b, c, d: An example of a correctly made opening for deaeration and bleeding in steel structures
  • Example d) In larger structural elements, one should take care that, during a galvanization process, considering possibly larger surface to be galvanized and taking into account that the higher the dimensions, the higher is surface roughness, large amount of ash may be produced and it has to come out onto the surface. Accordingly, such elements have to be thoroughly inspected prior galvanization in order to determine required quality and suitability of made openings and holes.

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  • Incorrect

  • Figure 5 Examples of correct overlapping, joints made by overlapping and correct distances between joined elements of the structure

  • Here, only some of the most frequent cases when overlapped surfaces create dangerous pockets are presented, i.e. ways in which these are secured against explosion. For distances between single elements the following applies: the smallest possible admissible distance between two elements of the joint, which is to be galvanized, cannot be less than 4mm.

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  • Figure 6 An example of deaeration and bleeding of closed vessels
  • In closed vessels, there is a general rule for arrangement of technological holes (at end plate edges of closed surfaces). Possibly installed inlet and outlet pipes have to follow this rule, while ends of these pipes cannot enter interior of a vessel for more than one thickness of pipe wall at maximum. Pipes and openings have to be arranged in a way to enable simultaneous evacuation of burned flux, smoke and dust, and to disable creation of air pockets.

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  • Figure 7 a; b; c; Ends and defining a method for suspension

  • A location of holes for hanging elements onto the beam have to ensure tight and reliable acceptance and good handling, and as less as possible imprints and traces on the future galvanized surface. Although these imprints do not mean poor quality and are not a subject of reclamation, these may considerably impair good appearance of the product.

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  • Figure 8 Examples of supporting for avoiding deflections due to internal stresses

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