Millen & White
Method and system for detecting plate clashing in disc refiners
 A refiner plate clash detection system and method for plate clash detection is provided herein. The system includes a receiver for a first signal having a significant increase in level at at least one distinct predetermined frequency related to the clash and the characteristics of the discs of the refiner. A filter is provided having a passband matched to pass the distinct frequency of the signal to provide a filtered output signal in which the center frequency of the passband of the filter is determined by the formula EQU f.sub.o =n.SIGMA..sub.R wherein PA1 f.sub.o is the center frequency (expressed in Hertz) of said passband PA1 n=the number of segments at a given radius, per single disc and PA1 .SIGMA..sub.R =the sum of the rotational rates (expressed in Hertz) of the two discs enclosing a given refining volume. The filtered signal is then smoothed. A threshold level is established. A comparator is provided for receiving the smoothed signal and for comparing it with the threshold level, and for providing an output signal of predetermined form, when the smoothed signal exceeds the threshold level. A receiver is provided for receiving the output signal for generating an alarm operation signal in response thereto. Protection can be automatically initiated by the plate clash detection system; alternately, it can be done manually by an operator, using the detection system as a warning device. 
Pulp and Paper Research Institute of Canada
D B D B
D21D B02C D21D B02C
inventional inventional inventional inventional
James H. Donald J.
Rogers Butler