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Preparation of constructions for galvanizing



Materialfor galvanizing should not be painted, stained with tar or large layer of oil or grease. Material should not be marked by plaster, paint or marker. On the surface there should be no errors of double plasticity, rolled cunder, rolled emulsion or impurity, welding paste residues. The pipes and corners must be cleaned of any residue after blasting (sand).




It is necessary topredict the hole on each element for binding the structure. For elements up to 1900 mm, an opening on the top is needed up to 20 mm distance from the end. Elements of more than 1900 mm need two holes, one on each end. Hole diameter depends on the size and weight of the structure. Minimum hole diameter is 8 mm.

Openings for  connection of  U and I profiles


Forprofiles of more than 5 meters long openings should be far from the end to prevent bending of the elements. 




Each element or structure must have openings for:
- Input and output of zinc
- Exit of air from the closed pipes and angles
- Openings must be in the upper end and lower end points, close to the places of welding seams
- Size of technological holes must be at least 30% of the diameter of the pipe.
If the galvanizing hollow body has no holes, air and moisture upon heating and rapid expansion could lead to an explosion.
There should be enough free space on the object for the input and output of zinc and exit of air during the process of hot-dip galvanizing.
With transverse stiffeners, it is better to provide a (pen) skew of the holes in the corner. For carriers that end with plate it is possible to provide appropriate holes as in the drawings: 







It isnecessary to drill holes in fences at all technological pipes as shown in the picture.
Technological openings must be adjacent to the welded seam.
In the examples you can see where technological openings are needed. Hollow structure must have openings for entry and exit of zinc and air outlet. Openings must be at least 30% of the inside diameter of the pipe.


If youhave a rectangular or square tubes welded on both sides and in set there is a need to punch technological holes like in the picture:


Technological holes should be drilled atcarriers onboth plates and in all stiffened parts cutting should be as in detail "A".


-Best is- completely open, "the same diameter" as the intersection of the bottom and top.



Tubularcolumns with the board. Places of technological openings:



Location of the opening:


1. The most desirable- completely open, "the same diameter" as the intersection of the bottom and top.
2. and 3. Equal replacement if complete opening is not possible.

4.  Must be used with 2 or 3 if the holes are not allowed in the top section - Two round 180° away in the line with holes 2 and 3.
For lighting poles there is a need to drill technology holes like in the picture:



Constructionof Ø 76 mm pipes and larger

Places of technological openings for entry and exit of zinc and air outlet for vertical and cross angle. Indicated by arrows in the drawing:


Tanksshould be constructed so as to allow complete and unobstructed drainage of zinc and air outlet. Connections to the reservoirs should be completed along with the tank wall.

Thefollowing cases show the correct hole for input - output of zinc and air outlet:


Closed "U" profiles should have holes in the corners for the input – output of zinc and air outlet



- All sides of thecontainer should be preferably have gutters.
- Bottom of the container must have a technological hole according to detail "A". Necessary technological openings are given in the drawing.
- On the sides of the container with no gutters there will be more or less deformation during hot dip galvanizing


Forthe beam shown in the sketch technological openings are needed according to details.

- The topsshouldbe compactand completelycleaned

Ifthere is a possibility of creating a "pocket" of the three sides, one side must be opened (15/45 degrees).





Evaporators, refrigerators must have "vent" (exhaust pipe) that is welded or attached by copper - asbestos gasket.
The pipe should be long 400 - 500mm and fitted so that at total immersion in a zinc of hollow body, the tube remains comfortably above the surface, so that zinc can enter the hollow body.

Thesestructural components must be tested to the pressure, must have a tin table with the number of certificate that guarantees the correctness of the hollow part. In the factory we can galvanize evaporators, fridge of 300l maximum capacity. After the test hollow body should be emptied of media that has been used for testing  correctness of evaporator, cooler.

Due to thespecific galvanizing of such structure a performer of galvanizing should be consulted.



Construction thatis delivered to the galvanizing should be properly packed, so it is possible to unload a forklift and not damage the elements.
Construction that is delivered and not properly packed for transport may suffer mechanical damage, for which the galvanizing contractor is not responsible.

Example of proper storage :