Pulp Paper & Logistics
HEIMBACH 21
Jet speed (back layer)
Fabric speed (back layer)
Figure 2: Both fixed measuring points in the filler position
For this test it is essential that all control parameters – including the adjusted ratio – are maintained. If then 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 was found quite conclusively: When the slice opening was changed from 20.6 to 21.2mm the jet speed was perfectly constant – however, measuring values and display consistently indicated a difference of just under 35 m/ min.
Therefore it was concluded
that there was really only one single factor responsible for the different readings.
Clarity achieved The next series of measurements was performed in the filler. This is a crucial factor for achieving overall sheet strength and comprises more than 80 per cent of the total sheet mass. The jet was permanently 28 m/min slower than displayed. From experience the customer’s
Figure 3: Measurement results in the top layer
papermakers 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 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 trouble shooting 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 will make another visit to the customer to test the jet speeds once more.
March/April 2017
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