Diagnostics of Bolted Joints in Vibrating Screens Based on a Multi-Body Dynamical Model

Abstract

The condition-based maintenance of vibrating screens requires new methods of their elements’ diagnostics due to severe disturbances in measured signals from vibrators and falling pieces of material. The bolted joints of the sieving deck, when failed, require a lot of time and workforce for repair. In this research, the authors proposed the model-based diagnostic method based on modal analysis of the 2-DOF system, which accounts for the interaction of the screen body and the upper deck under conditions of bolted joint degradation. It is shown that the second natural mode with an out-of-phase motion of the upper deck against the main screen housing may coincide with the excitation frequency or its higher harmonics, which appear when vibrators’ bearings are in bad condition. This interaction speeds up bolt loosening and joint opening by the dynamical loading of higher amplitude. The proposed approach can be used to detune the system from resonance and anti-resonance to reduce maintenance costs and energy consumption. To prevent abrupt failures, such parameters as second natural mode frequency, damping factor, and phase space plot (PSP) distortion measures are proposed as bolt health indicators, and these are verified on the laboratory vibrating screen. Also, the robustness is tested by the impulsive non-Gaussian noise addition to the measurement data. A special diagram was proposed for the bolted joints’ strength capacity assessment and maintenance actions planning (tightening, replacement), depending on clearance in the joints.

Generating rectilinear, elliptical, and circular oscillations of a single-mass vibratory system equipped with an enhanced twin crank-type exciter

“…The improved (more accurate) mathematical model of a flip-flop vibratory screen loaded by the materials being processed is derived in [2]. The prospects of performing the diagnostical operations and predicting the service life of the vibrating screens are thoroughly studied in [3]. Considering the performance of the vibratory screening equipment, the authors of [4] investigated the influence of the external moisture content and the screen type on the efficiency of stratification and dewatering of different materials.…”

The Impact of Vibrating Screen Startup Time on Vibration Amplitude and Energy Consumption in Transient State

“…Using motors with excessive power reserves can adversely affect the power grid (significant reactive power) and increase the vibrating mass. In most cases, research on screens is limited to steady-state studies [15,18] and studies focused solely on the screening process using DEM simulations [19][20][21][22][23][24]. There are also attempts to develop vibration models that would consider the screened material's influence on the vibration parameters.…”

Optimal Vibration Fields in Problems of Modeling Dynamic States of Technical Objects

“…Еще одна обширная группа задач, требующих оценки динамических состояний элементов, -вибрационные процессы технологических машин [12]. Так, динамическое состояние машин вибрационного грохочения зависит от формирования динамических состояний нескольких корпусов, которые можно рассматривать как твердые тела с учетом характера упругих связей между ними [13]. Существенный фактор, определяющий динамические состояния объектов технологического назначения, -частота колебаний [14].…”