Working principle of an electromagnetic wiping system

R. Ernst¹ - Y. Fautrelle¹ - A.-M. Bianchi² - M. Iliescu²

¹ SIMAP (EPM) Laboratory, Saint Martin d'Hères, France
² Technical University of Civil Engineering Bucharest, Romania

Abstract
In galvanizing lines, the gas knife wiping device works well for controlling the zinc coating thickness up to 2 to 3\,m/s strip velocities. But for higher velocities, a strong liquid zinc splash risk forbids the gas pressure increase, which would be necessary to keep the same thickness control efficiency of the knives. That is why a complementary electromagnetic wiping system, whose purpose is to pre-wipe the liquid zinc before the gas knives take over, is presented here. After mentioning different kinds of AC and DC possible electromagnetic solutions, a DC field electromagnetic brake (EMB) system based on the use of permanent magnets is selected for a future experimental implementation. In order to better understand the electromagnetic and fluid mechanics phenomena, an analytical model and then different numerical models are presented here. These models show an interesting wiping effect on the liquid zinc, which seems promising for a future experimental pilot design. Figs 8, Refs 9.