Computer controlled galvanizing

In the galvanizing process excess zinc is coated onto the steeL strip to ensure that the finished product exceeds coating quaLity standards. Reducing the excess coating to a minimum whiLe maintaining product quaLity can significantly reduce a company's zinc bill. A computer based coating-mass controL system has reduced zinc consumption by thirteen percent on a gaLvanizing Line saving in excess of one million dolLars annually. The same system has been installed on a zincalume line with similar results. The most significant time constant in the process is the transport delay between coatingmass control and measurement. Feedforward contol, using a simple model and a table of adapted constants, compensates for this during major changes in process conditions. Feedback control, using a self-adapting linear incremental model, maintains the coating-mass within range during steady-state conditions.