Distortion during the hot dip galvanizing process is relatively rare.
On those few occasions when distortion does occur it usually could have been avoided or the risk minimised during the fabrication design stage.
As galvanizers we know that certain fabrications are more prone to distortion than others. The one thing that we can do to lessen the chance of distortion is to dip the fabrication as quickly as possible.
The fabricator, on the other hand, can follow a number of principles (shown below) during the design and fabrication process to help us. See our Guide to Distortion.
It helps if your galvanizer can dip the fabrication in one go (rather than double dipping) so check with them that your fabrication will fit into their bath before you fabricate. If it does not fit then you may want to consider fabricating it in more than one piece.
We cover venting and drainage in more detail elsewhere but it is also worth mentioning here that large and numerous vent/drainage holes will enable us to dip your fabrication as fast as we can and will help minimise the risk of distortion.
Plate fabrications such as tanks, troughs etc will often benefit from bracings or stiffeners (of the same thickness as the plate).
Control your welding procedures during fabrication. Do not ‘over weld’ and arrange the seams symmetrically if possible.
Steel thickness combinations
Large differences in steel thicknesses on the same fabrication should be avoided if possible. For example, welding 3mm thick plate to 10mm thick box section is a recipe for distortion as both sections will heat and cool at different rates and so cause contracting stresses which can ripple or bend the plate and ‘pop’ welds. Another principle to help reduce or minimise the risk of distortion is to increase the thickness of steel sections used as the thinner the section is, the less chance it has of withstanding its tendency to distort.