MEASURING FORCES IN A REFINER PLATE GAP

In order to gain more understanding regarding the processes active in a refiner plate gap during refining, it is of interest to k818 mow how the total energy input to the refiner is distributed over the refiner plates. This distribution can easily be calculated provided the distribution of tangential forces is known. In this study is presented a force sensor by which it is possible to measure, in a sustainable way, the forces in the plate gap of a single disc refiner. The sensor is in the form of an instrumented, hollow radial bar where the instrumentation consists of strain gauges mounted pair-wise in eight radial positions on the inside of the bar. In this way, the strain gauges are protected from the harsh environment in the plate gap. Now, knowing the stiffness properties of the bar, it is possible to calculate the tangential forces from the difference (i.e. subtracted signal) of the measured strains in each position. Moreover, for reasons other than calculating the energy distribution, it might be of interest to know the normal forces on the sensor and these can be calculated from the summed strain values together with relevant stiffness properties. The sensor, the theory behind and the calibration procedure is presented and discussed.