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WORLD PULPPAPER 59 findings first at equal dosage level in terms of active chlorine content the different species of stabilised chlorine compounds demonstrate corrosion rates of widely different magnitudes. Secondly laboratory experiments can never fully demonstrate the true corrosion potential in vapour phase in an individual paper machine due to machine specific moisture conditions and in-situ reactions of chemicals in white water. Therefore we developed an on-line probe for measuring changes in vapour phase corrosion rate. This probe is sensitised so that it corrodes all the time and responds to chemical changes in vapour phase thereby giving a possibility to observe changes and react before corrosion occurs in the machine. More information on biocides and corrosion is shown in Figures 3 and 4. As a result of studies both in the laboratory and mills we have created a complete package to reduce corrosion risks to machines while at the same time ensuring hygiene in the board products. CONCLUSION Safely achieving hygienic conditions on a food packaging board machine is not simple. The mechanisms of contamination and corrosion are both complex and require expertise for control. We have shown that there is no direct correlation between the level of aerobic bacteria and the level of spores the true enemy as they can survive the heat of the dryer and contaminate your finished product at a high cost. Kemira has gained significant market share within hygienic board by successfully controlling spore formation mechanisms. Close co-operation among our Sales Applications and RD groups with the board mills has provided customers with clear competitive advantages stable production combined with continuous improvement in hygienic quality. Long-term control of bacterial spores on a board machine requires special competence to select the best control strategy for each individual machine. There is no universal spore control philosophy that best fits all machines Figure 3. Kemira CorrStrix on-line data from a folding boxboard machine. A new biocide program was started after shutdown with no other changes done in the wet-end of this board machine. The average rate of vapour phase corrosion at dryer section reduced by over 75 when compared to the previous biocide program. The complete package for hygiene control Kemira FennoClean Corrosion-safe biocide products in the machine On-line monitoring tools for of biocides such as CorrStrix Know-how and products for controlling spore formation Centralized data management and analysis tools KemConnect for follow-up Systematic co-operation with customers enabling continuous improvement in hygienic quality Safely achieving hygienic conditions on a food packaging board machine is not simple. The mechanisms of contamination and corrosion are both complex and require expertise for control