Publication Date

1982

Abstract

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.

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