Design of Structures

A few basic rules that should be followed when designing products for subsequent galvanizing.

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  • Follow designer’s instructions with regard to holes drilled in hollow structures. 
  • Ensure additional clearance of approximately 1.5 mm on each side. 
  • Avoid, if possible, overlapping surfaces. If that is impossible, follow strictly rules on drillings. 
  • Remember that galvanizer has to lift and turn your articles. Make sure that you have ensured possibility to lift your article. 
  • Avoid combining materials of different thickness that can cause deformation due to different cooling time. 
  • Avoid big size thin metal sheets. Unless stiffened, they might warp.


Designing Holes

When designing hollow steel articles, proper size and dislocation holes should be provided for zinc drainage, as well as venting upon influx of zinc. In case that is not ensured, there is a risk of two things to happen. Firstly, structure may explode upon on immersion in zinc bath when internal moisture turns into vapour. Secondly, steel will not be covered with zinc from inside since it will not get inside. Galvanizer will drill holes instead of you but it is much more difficult to drill in a ready structure without auxiliary devices therefore the price of one such drill can be very high. 
There is no need to cover these holes after galvanizing since airflow through hollow section ensures better conditions for life cycle of zinc coating. In case of necessity to close the holes, plastic or aluminium cone plugs should be used.

Recommended Size of Holes (mm)

Length of the article 0-2000 2000-4000 4000-6000 6000-8000 8000-10000
Size of the pipe          
0-25  8 10  12  12-14  14-16
25-50 8-12  10-12  12-16  20-30  25-30 
50-100 12-20  12-30  15-30  30-50  30-50 
100-200 20-40  30-50  30-50  50-80  50-90 
200-300 40-80  50-100  50-100  100-120  100-130 
300-400 80-100  100-120  100-120  120-150  100-160 
400-500 100-150  120-200  120-200  200-250  200-300 
500-600 150-200  200-250  200-300  300-350  300-350 

These dimensions refer to all types of hollow beams, UNP and IPE beams, as well as welded hollow structures.
Taisnleņķa atbalsti Read more

Right-angled supports

When designing right-angled supports or similar structures, holes should be drilled in places indicated in the drawing.

V veida iegriezumi Read more

“V”-type notch

“V”-type notch is a good alternative to drilled holes.

I un U veida profili Read more

Universal sections or channels

On universal sections or channels, make sure that the corners of stiffeners are cut to allow zinc to drain through.

Ārējie balsti Read more

External props

When you use external props, for instance, between a base plate and a vertical element, make sure the prop is cropped to allow zinc to drain freely.

Leņķu konstrukcijas Read more

Stiffeners and gusset plates

Always design stiffeners and gusset plates so that zinc cannot be trapped in corners.

Iekšējā diafragma Read more

Internal diaphragm

When using internal diaphragm, make sure the corners of it are cut. On larger RHS use a stiffener with a central hole as well as cut corners. NEVER arrange a plate that blocks the entire cross section. It may be dangerous during hot dip galvanizing. (One may happen to be unpleasantly surprised when receiving an invoice if the entire section has filled with zinc which cannot escape!)

Urbuma izvietojums Read more

Direction of holes

Place the holes as close to corners as possible! As well proper direction of holes should be considered. It heps the galvanizer if the holes all drain in the same direction. This avoids manipulating and turning of the article with risk of damage or trapping zinc in pockets.

Drenāža Read more


When designing or producing structural hollow structures, remember to provide for each separate element appropriate drainage. The technological holes must be located at the ends of the pipes on opposite sides diagonally.

Virsmu pārklājumi Read more

Overlapping surfaces

Avoid overlapping surfaces as much as possible. If this is not possible, strictly follow the drilling instructions.