Design right for galvanizing

When using steel in construction, hot dip galvanizing is an essential part of the project to protect the longevity of the metal. You carefully design your steel to fit the overall build of the construction project. But sufficient care and attention are also required when you design your steel for galvanization. A good design will prevent any processing problems at the galvanizing plant and will also ensure you get the best steel coating possible.

Here’s some key design pointers to enable your steelwork to be processed safely whilst giving you the best quality coating.

When sending steel to a galvanizing plant, you will have several goals in mind:

1. Fast turnaround
2. Premium quality coating
3. Excellent service
4. Good value for money.

Ensuring steelwork is suitably designed for hot dip galvanizing helps achieve these goals and ensures the steel is safe to be galvanized. Poor design can result in poor coating quality, additional costs, low production rates, and failure to meet delivery dates. Poor design can also pose serious health and safety risks for the people carrying out the galvanizing.

What does good design look like?

The importance of venting and drainage

When steel is immersed in the galvanizing bath, add vent and drain holes to sealed hollow sections or cavities to ensure superheated air can escape all internal spaces and the molten zinc can flow freely over all surfaces, external and internal. Failure to adequately vent would result in trapped air causing an explosion and endangering galvanizing workers. It would also cause zinc build-up where the excess zinc cannot drain properly.

The sizing and location of vent holes are just as important as the provision of these holes. As a guide, make the venting holes as large as the steelwork can manage (but talk to your galvanizer for the best advice for your fabrications). The hole locations will be determined by how the steelwork is hung on the jigs at the galvanizing plant.

When adequately sized and correctly located, vent and drainage holes will:

• Significantly reduce the risk of injury to galvanizers.
• Allow faster immersion and withdrawal speeds which will help to minimise excessive coating build-up and reduce the risk of distortion by minimising temperature differentials.
• Virtually eliminate the risk of damage to product, plant and equipment caused by the explosive vaporisation of entrapped moisture or air.
• Improve the characteristics of the galvanized coating by restricting the effects of zinc solidification during drainage and reducing the mass of zinc required to achieve a good finish.

Size, weight, and shape matter

To ensure a good hot dip galvanizing finish, size, weight, and shape really do matter. A fabrication design should ideally incorporate easily handled components or fabrications which can be single dipped or subsequently assembled by bolting with galvanized fastenings. Double dipping is a possible alternative. Seek advice from your galvanizer before proceeding.

Suspension holes or lifting lugs may be needed if there are no suitable points for locating hooks or wires. Once again, lifting points should be positioned to maximise venting and drainage.

Minimising distortion

You will not want your steelwork to become distorted during the galvanizing process. To minimise distortion, fabrications should ideally be symmetrical, suitable for single dipping, and incorporate sections of as near equal thickness as possible at the joints. Components should also fit perfectly to avoid force or restraint during joining. Use continuously welded joints with balanced welding techniques to reduce uneven thermal stresses and the largest possible radii on all curved members.

Design is just part of the story. It’s also essential to choose your galvanizer wisely

As well as following the rules of good design for pre-galvanized steel, take care when choosing your galvanizer.

Health and safety standards

Look for a plant with exemplary health and safety standards. One where the plant managers work hard to keep all colleagues and visitors safe with up-to-date equipment, sufficient PPE, good air quality, and clear-to-follow rigorous shop floor processes. And one where team members work safely on every job by thoroughly inspecting steel from the point it is delivered and at key intervals of the galvanizing process to ensure projects will not pose health and safety risks.

Training

Look for a galvanizer that not only trains team members on all aspects of safety in galvanizing, but also teaches clients and the wider industry. At Premier Galvanizing for example, we issue ‘Safe Design for Hot Dip Galvanizing’ posters to our clients as reference guides for steel preparation. We’ve also published a ‘Design for Galvanizing’ video (available on our website and YouTube), and we run ‘Design for Galvanizing’ seminars onsite for client teams.

Technical help

A final piece of advice is to always look for a galvanizing company happy to be on hand to provide technical advice on all aspects of pre-galvanized steel preparation.

Premier Galvanizing has a Technical Support Team who will answer any steel fabrication questions from clients. The team members are also happy to visit fabrication shops and advise on venting requirements to ensure fabrication issues can be resolved before the steel reaches the galvanizing plant.

We hope you’ve found these pointers helpful. For more information, please get in touch with a member of our team. There is also lots of helpful information freely provided by the Galvanizers Association.

Next page