Vibration Analysis of Copper Ore Crushers Used in Mineral Processing Plant—Problem of Bearings Damage Detection in Presence of Heavy Impulsive Noise

Abstract

Vibration analysis of rolling element bearings (REB) used in copper ore crushers is discussed in the paper. The purpose of the analysis is to detect localized damage in REB. The problem of damage detection in REB is widely described in literature, in general. However, known techniques might be not successful in case of crushers due to presence of heavy non-Gaussian, impulsive noise. Impulsiveness of the signal from bearings is commonly used as an indicator of damage as well as a filter optimization criterion in order to enhance raw observation (to extract informative part—signal of interest (SOI)). A crusher is a kind of machine which use a metal surface to crumble materials into small fractional pieces. During this process, as well as during entering material stream into the crusher, a lot of impacts/shocks appear. They are present in vibration signal acquired from bearing’s housing. These non-periodic, strong impulses are non-informative from diagnostic point of view and should be removed from the raw signal before further processing, because they mask completely informative, cyclic impulses related to damaged part of REB. Unfortunately, impulsiveness cannot be basis for signal extraction anymore. So, commonly used kurtosis-based optimization of pre-filtering (kurtogram, spectral kurtosis) cannot be used here. Promising approach is to search for cyclic/periodic nature of impulses (envelope analysis, spectral correlation density, protrugram, etc.). However, as mentioned, even before enveloping there is also a need to pre-filter the signal. In the paper we will introduce the problem including description of the machine, investigation on structure of vibration and we will present preliminary results of vibration processing using protrugram approach. At the end, we will propose an enhancement of protrugram in order to identify cyclo-stationary signal in presence of randomly spaced impulses and narrowband amplitude modulation of discrete components.