Broken Hill Proprietary (BHP) is a large international iron/steel/oil conglomerate that had a research complex in Melbourne, Victoria, Australia. I was fortunate enough to earn a position there in 1972 that eventually, in 1977, became a research post as the electrical member of an internal think tank tasked with finding new technologies to widen BHP’s operations. Other companies within the BHP group were encouraged to consult us on any topic that related to their operations.
One such other division is Australian Wire Industries (AWI), which makes wire and wire products. One of its primary products is galvanized wire that is commonly used for fencing and the basis for many other products. The galvanizing process used was hot dipped, where the wire was fed into a large bath of molten zinc from which it would exit vertically to allow the excess zinc to run back into the bath. The primary problem was the speed at which the plant could be run while maintaining an acceptable finish and coating weight on the wire. Industry practice was to have a gravel bed at the point of exit so the excess would be scraped back.
AWI discovered that introducing a sulfur-bearing gas into the gravel bed caused the formation of a strong film of zinc sulfide to quickly form and not only aid the zinc retardation process but also give a very good smooth finish, which is commercially important. AWI’s patents were licensed worldwide, and it came to us to find a new method for the process (called gas wiping) so it could maintain leadership in the industry.
We discussed the problem at length and finally decided it was too hard for an advanced chemical or mechanical approach, so my idea of an electromagnetic liquid metal pump was given the task. All I had to do was develop an electromagnetic device that could operate in a 400-°C (750-°F) environment. After considerable research into liquid metal pumping and the rheology of zinc, I designed and built a small (150-W) three-phase cylindrical pump that barely worked on the bench, but the revealed frequency was not as important as expected. The next version was more robust (2 kW) and made to operate while immersed in zinc at 400 °C. My materials problems were eased by the company’s steel division, which had experts on high-temperature materials and who were very helpful supplying all my needs.
The next discovery was that a single-phase coil could provide results equal to the polyphase design, so we upped the power to about 4 kW and made the pump open sided and suitable for 10 wires, a requirement for production applications. I constructed the pump from square copper conductor wound on a stack of laminated C-core halves with plenty of alumina paste to hold it together. Our patents are 41664/78 (Australia) and 4228200 (USA). My work continued with a bench-scale simulation rig using gallium liquid at 40 °C, where I attempted to plot the flow around the exiting wire using Faraday probes.