EVALUATION OF SMRI'S DRI MACHINE FOR MEASURING CANE PREPARATION

MOST RAW sugarcane factories measure cane preparation in order to assess shredder performance. Traditionally, cane preparation has been measured by the pol in open cells method or the preparation index method. In both cases, two cane samples are processed with the easily accessible pol (the pol in open cells) determined from a gentle washing process and the total pol determined from a disintegration process. The pol in open cells measurement, while recognised as the best measurement available, is known to have a high analytical test error of about two units and, because of the need to process two cane samples, is expensive to measure. As a result, Australian factories have reduced the number of pol in open cells measurements to an average of about one a day. Obtaining one measurement a day is not enough to adequately track shredder performance. Negative sentiment towards the preparation index measurement exists in South Africa also. The DRI (diffusion rate index) measurement is an alternative measurement of preparation that has recently been developed by the Sugar Milling Research Institute (SMRI) in South Africa. The DRI measurement procedure is similar to the gentle washing process used in the pol in open cells measurement. While the pol in open cells measurement is based only on the pol of the extract at the end of the washing procedure, DRI is calculated from the rate of increase in brix concentration (as measured by conductivity) throughout the washing procedure. Unlike the pol in open cells procedure that takes approximately an hour to complete, the DRI measurement procedure takes only about ten minutes. SMRI and SRI have both undertaken tests to compare pol in open cells (or preparation index) to DRI. DRI has an analytical test error of about 0.7 s while pol in open cells has an analytical test error of about two percentage units. On a relative scale, the error in the DRI measurement is about the same as the error in the pol in open cells measurement. Experimental results show that there is a relationship between DRI and pol in open cells with low DRI values corresponding to high pol in open cells values. Given that DRI and pol in open cells have similar precision, the big advantage of the DRI measurement is its ten-minute cycle time. Shredder performance can be determined at a lower cost or can be determined with greater precision through more regular measurement.