Condition Monitoring of Vibrating Sieving Screens—Design, Dynamics and Diagnostics

The diagnostics of sieving screens and other vibratory machines is the most complicated scientific and engineering task due to a permanent periodical (technological) excitation and stochastic impulsive (non-Gaussian) disturbances from the falling pieces of bulk materials, which directly influence the reliability of damage alarming in the condition monitoring systems. In the design of sieving screens, the most critical parts are supporting springs, inertial vibrators with special types of bearings, and bolted joints, which are subjected to severe cyclic fatigue and experience hardly detected loosening. All these elements require frequently scheduled inspections. To provide prevention of abrupt failures and reduction of maintenance costs with simultaneous energy saving and output product quality, a new approach is developed, which is based on multi-body nonlinear dynamical models and advanced methods of signal processing with an emphasis on transient periods of screen operation when the natural modes of vibration are excited. Models and diagnostic methods are verified on real case studies. Some new features are discovered in the screen dynamics. In addition, the new concept of double-frequency coaxial vibrators provides certain operational advantages compared to separate driving motors. Besides, multi-frequency regulated excitation of screens is generated with a wider spectrum of vibrations, which increases sieving process performance for fine-grained materials addicted to cohesion.