MONITORING JAW CRUSHING PARAMETERS VIA VIBRATION SIGNAL MEASUREMENT

Fine crushing tests were performed on a laboratory scale jaw crusher with dry, monosize dolomite. The source vibration signal was picked up by an accelerometer, the acceleration signal was amplified by a vibrometer, and then stored on a DAT recorder during whole testing period. For each crushing test, three vibration signal samples were taken and converted into an IBM PC accessible data format using a digital oscilloscope. The digitised vibration signal was analysed with the aid of digital signal processing technique. Through spectral inspection and principal component analysis, it was found that two major frequency bands, 250-400 and 700-900 Hz, were strongly related with the variation of the operating parameters. The first four principal components account for 91% of the total variation of the vibration signal. It was found that the inter-particle collision and attrition without breakage mainly affects the energy of the 250-400 Hz frequency band, and the variation of the frequency band of 700-900 Hz characterises the breakage events of dolomite. With the aid of the multivariate data analysis, the relationship was established between the power spectral density and the operating parameters such as the feed rate to the crusher, the close side crusher setting and the charge volume of dolomite in the crusher chamber. The product size distribution described by Gaudin equation was also related to the vibration signal. Thus, an alternative method for monitoring the operating state can therefore be developed through measuring and processing the vibration signal from crushing.