Control technique for a multi-stage washing process that uses a plurality of chemicals

摘要

Equipment and a method for a system implementing a multistep washing process using a plurality of chemicals. The system comprises a chemical container (110A to 110D) for each chemical (111A to 111 D) and means for conveying one chemical at a time from the chemical container through a feed channel (120) to a washing object (100) and from the washing object through a return channel (130) back to the chemical container. The first and the second sensor means (122, 132) which monitor the first parameter set in the feed channel (120) and the second parameter set in the return channel (130), respectively. Both parameter sets include at least one parameter indicating directly or indirectly the purity of the chemical. A control centre (150) includes calculation means (153), which are arranged to determine the mutual uniformity of the first and the second monitored parameter sets, and decision means (154) whereby the action time of the chemical is determined on the basis of the mutual uniformity of the first and the second monitored parameter sets.