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world pulppaper 37 fibre consistency and ash control audits can reveal where improvements in stability can be made in screening cleaning disc filter operation and dilution figure 5. A typical fibre fractionation instrument layout More precise consistency control will improve the operation of many of the unit operations in a fibre fractionation plant. Fibre consistency and ash control audits can reveal where improvements in stability can be made in screening cleaning disc filter operation and dilution. These audits also measure long and short fibre separation fines and fibre morphology as well as process operating conditions. For instance screen feedstock consistency requires very tight control since it influences screen throughput and runnability screen blinding and can also determine the quality. An increase in consistency will increase throughput but can increase the risk of blinding. A large variability in consistency can upset the screen reject rate and cause disturbances to efficiency fibre quality and freeness. In one case with variations in consistency of 0.9 the screens act as fractionators and unexpectedly remove long fibre from the process resulting in lower efficiency and lower strength. concluSIonS Strategically applied inline measurements within a recycled fibre operation can yield many benefits including stable product quality even throughput increased yield lower furnish costs and lower chemical and bleaching costs for DIP. These measurements can form the basis of operator managed controls or simple single loop controls that are inexpensive to implement. The return on investment is excellent. Multi- variable controls APCs have shown promise as a way to control RCF plants however they must be based upon reliable and accurate process measurements of controlled and manipulated variables. The message is clear a stable and efficient RCF operation must be well measured.