plating, anodizing, & finishing Q&As since 1989
Change of the kettle?
Q. We have a kettle from Germany have a capacity of zinc 400 tons & dimensions 15m* 1.6m * 2.5m it had been worked since 5 year before .
What is the best time to change it?
What is the possible tolerance for buckling in the sides?
Thank you very much
power& telecom - Cairo, Egypt
A. This is a tough call. There are so many factors to be considered. Kettle life can range from weeks to over 10 years, with 5 - 7 years most common for scheduled changes. Some of the factors are:
-Kettle maintenance;how well you dross, cleaning of skim line, keeping zinc level above heat zones, Etc.
-Temperature control: allowing kettle to overheat, running temp. too high.
-Amount of work; if you push the limits with a high BTU input, life will be shortened.
-Washing; some processes have a tendency to "wash" the walls, causing localized wear.
These factors all come into play along with others when it comes to kettle life. If you have not been probing the walls, you should begin doing so at least every other month, if not more often. Log and map any suspicious spots to keep a close watch on. The bowing of kettle wall should be kept at a minimum by properly designed bracing. I have seen a kettle that was approx. 10 meters long x 1.2 meters wide x 1.8 meters deep bowed out to 2 meters in the center.....not long before the walls gave way and they lost everything. I would not be too concerned with 10 centimeters wider in the center, although good bracing should keep it under that.
At the least, you should have a replacement kettle on hand, and someone competent to do the change over.
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