SPEED MEASUREMENT SYSTEMS WORLD PULP&PAPER 16 the measurements in the surface layer (Figure 3) were performed. The results of both the filler and the surface layer confirmed what had already been found in the back layer: only one single source of error made sense! JOB DONE – CUSTOMERS SATISFIED Now it was possible to tell the customer with absolute certainty: fabric and jet were perfectly adjusted in all three layers, which meant that troubleshooting could be focused on the area of data processing. Either the software itself or its specific programming was the source of the problem. From this point onwards the collected measurement results can provide the customer’s software experts with the basis for correcting the calculation of the jet speed. Once this has been done, TASK then make another visit to the customer to test the jet speeds once more. Any changes… are an indication that in principle the entire system has to be checked logically assumed that the jet was 10m/min faster than the fabric and therefore more fibres were aligned in a cross direction. In fact, the jet was actually 25m/min slower than the fabric and therefore the fibre orientation followed tended more to the machine direction. TASK therefore increased the jet speed until a real ratio of 0m/min was achieved. SLICE OPENING AND JET SPEED After this had been accomplished the slice opening of the headbox was changed in order to find out whether the jet speed remained constant. For this test it is essential that all control parameters - including the adjusted ratio - are maintained. Then, if only the slice opening of the headbox is changed (flow rate higher or lower), the jet speed has to remain constant. Any changes, however, are an indication that in principle the entire system has to be checked. In the back layer, something quite conclusive was found: When the slice opening was changed from 20.6 to 21.2mm, the jet speed was perfectly constant – however, measuring values and the display consistently indicated a difference of just under 35m/min. It was therefore concluded that really only one single factor was responsible for the different readings. CLARITY ACHIEVED The next series of measurements were performed in the filler position. This is a crucial factor for achieving overall sheet strength and comprises more than 80% of the total sheet mass. The jet was permanently 28m/min slower than displayed. From past experience, the customer’s operators had suspected from the beginning that the display was incorrect. Together with the customer, the speeds were aligned (jet and fabric). After completion of the adjustments, the measured speeds matched. Finally Figure 3. Measurement results in the top layer.