Patent ID: 6749692
Filing Date: 2004-06-15
Classification: C23G,C25D

Abstract:
A method of operating a counterflow cascade washer for wet-chemical treatment of a surface of a metal strip and to be located downstream of one of treatment means and aftertreatment means of a metal strip treating installation, with the counterflow cascade washer including a plurality of washer units each having means for connecting a respective washer unit with a fresh water supply and a rinsing water circuit, the method comprising the steps of branching a portion of a water flow, which circulates through a rinsing water circuit associated with each of the washer units, off in form of a bypass stream; and feeding the bypass stream to a washer unit located immediately upstream of a respective washer unit for additionally rinsing the metal strip in the immediately upstream washer unit with a rinsing water containing a smaller concentration of foreign additives than a rinsing water with which the metal strip is first treated in the immediately upstream washer unit; and dividing the bypass stream at an end of the immediately upstream washer unit and feeding the divided water stream to locations above and below the metal strip.