We recently undertook a large capital project at our plant, with the changeover of our galvanizing kettle.
A galvanizing kettle weighs around 32 tonne and holds around 260 tonnes of molten zinc that heated to temperatures of 445°C to 465°C. And the kettle is used to immerse prepared steel items into the molten zinc, to galvanize them. This protects steel components from corrosion. As you can imagine, these kettles have a shelf life. They are regularly tested for integrity and generally have a life of 10 years +.
When it’s time to change a kettle, there is a high level of planning required. We worked on this project for about 12 months to commission the build of a new kettle and co-ordinate the installation, which occurred during our 2020 Christmas shutdown. Here is an outline of how the project was delivered.
THE REMOVAL PHASE
The first stage of the changeover project was to empty the existing kettle of all molten zinc. With a material’s cost of over $1M the zinc was pumped out of the kettle and into ingot moulds. The result was 30+ cubic metres of zinc to save for later use.
The next step was to dismantle the existing structure, primarily the kettle and the canopy. While the kettle holds the molten zinc for steel components to be immersed for galvanizing, the canopy’s role is to capture fumes from the gal process & protect our team from potential zinc splatter. The temperature difference between the fabricated steel (approx. 50°C) going into the tank & the molten zinc (450°C) creates a degree of splatter & the enclosed zone protects our team until the steel has reached the same temperature as the zinc and is safe to withdraw from the kettle.
When all the molten zinc was extracted from the old bath, evidence of wear & tear that occurs to the walls of the kettle over time was clear. Traditionally weak spots occur closer to the burners, which are constantly working to keep the molten zinc temperatures in that 445°C to 455°C range. It highlights why our asset management systems are so important, which includes regular kettle inspections and integrity testing.
THE INSTALLATION PHASE
Once we’ve removed the old structure, installation begins. With the help of Integrated Galvanizing Solutions (IGS) we were on schedule for the new bath and canopy to be installed and commissioned. The hands-on skills of our team and contractors enabled the project to run smoothly.
The new kettle is installed and loaded with new zinc ingots. The team ensures the ingots are packed as tightly as possible in the kettle to maximises heat transfer during the ‘heat-up’ phase.
Then the canopy is constructed around the kettle and the extraction system installed. We then replaced our control panel and updated the control programs to increase burner pulsing and efficiency. The completed hot dip galvanizing system is commissioned, then tested and the burners are activated for the ‘heat-up’ phase to melt the zinc. This phase takes 7 days to transition from solid zinc blocks to a bath of molten zinc.
Nothing goes to waste with the ingots produced during our kettle removal phase, scheduled to be added to the new kettle during normal production over the next few months.
PROJECT PARTNERS’ VIEWS
Our partner in this kettle changeover project, Integrated Galvanizing Solutions had this to say about the project.
“As travelling to site was not possible due to COVID, collaboration was key to the success of this project. We harnessed the talent of the Geelong Galvanizing team, in conjunction with local contractors. IGS was able to pivot and successfully supervise the kettle change, installation of a new furnace control system and the heat-up & melt-down of the zinc bath.
IGS’s supervision model uses planning and clear communication processes, systems that undergo rigorous factory testing prior to delivery, user-friendly, concise manuals and detailed assembly drawings to deliver a successful ‘plug & play’ installation onsite, using (in this case) remote supervision.”
A great effort by all our staff and installation partners to remove the old kettle and canopy, then install the new and commission the galvanizing system, all within 2 weeks!