4-2 The K. I. D.: A New Way to Perform Low Cost Ultrasonicdiagnostics on Hot-Dip Galvanizing Kettles

摘要

The ultrasonic probes and techniques for the wall thickness measurement of kettle containing a common molten Zn alloy for galvanization process at elevated temperatures are presented. Traditionally, the molten Zn has been partially or totally emptied from the kettle, applying a clad aluminum (Al) rod consisting of an Al core and a stainless steel (SS) cladding. Such probe has been fabricated and successfully used to measure the thickness of the kettle wall exposed to air and at a temperature of approximately 350℃ while the probe was cooled by a cooling system. The ultrasonically measured thickness profile of the kettle wall was proved to be useful to the galvanization industry as much as the visual inspection related to this mean of diagnostics. Of course, in time the mean of direct inspection involves molten zinc transfer and delicate safety matters, so a special cooling system for the immersion ultrasonic probe in which a strong ultrasonic strength commercially available room temperature UT can be used was developed. The cooling enables the temperature of the UT end of the immersion probe in molten Zn at 450℃ inside an industrial kettle to be within a comfort zone of temperature around 0℃. Following the success of the R & D stage, Zinco Service has implemented and successfully used a new revolutionary Kettle Inspection Device (KID) that allows low-cost, in line, non invasive ultrasonic inspection and kettle profiling of hot dip galvanizing kettles. Such technology allows collection of extensive data on kettle deformation, kettle thickness and also of iron-zinc alloy layer on the wall. Diagnostics have thus become standard practice, allowing a better understanding of the life and performance of steel kettles. Tens of kettles have been inspected in Europe and North America and data will be presented on the accuracy obtained, the usefulness of information as well as a comparison between this new technique and the previously available ones in terms of costs and time employed.