Vibration analysis is used for maintenance and fault detection of vibrating machinery. The purpose is to analyse how well the machinery is operating within its target parameters, while fault detection is done to diagnose and locate a fault that might be developing on the machinery and causing higher operational expenditure for the producer.
In addition to determining the mechanical condition of the vibrating screen, the analysis collects data on parameters such as natural frequencies, revolutions per minute (RPM), stroke, amplitude and G-force. Armed with this critical information, one can pursue the ideal screening performance by optimising screen parameters in a way that means particles find as many opportunities as possible to pass screen openings.
{{image2-a:r-w:200}}Recent vibration testing at Australian quarry operations revealed 50 per cent of vibrating screens tested were in critical, serious or problematic condition, and required attention to prevent imminent breakdowns or rectify inefficient screening performance.
A common condition among most sites was inadequate acceleration on some screens and excessive acceleration on others, with G-forces ranging from 3.2G to more than 5G. The optimal range for maximum screening efficiency is about 3.6G to 4.2G, depending on the material and the type of screening machine (Figure 1).
When the G-force is too low, there is insufficient energy to launch pegged and near size particles out of the apertures. Damp sticky fines can cling to the screen media surface, resulting in loss of efficiency through blinding. When the G-force is too high, the material is thrown higher and further down the screen. Stratification is poor and there are far fewer opportunities for particles to pass through the screen openings. Power consumption and wear on components increases while screening efficiency decreases (Figure 2).
When optimum machine performance is achieved, the results are higher production capacities, greater product quality, reduced maintenance requirements and lower costs per tonne for material produced.
Nepean Rubber now provides the PULSE Vibration Analysis service together with Haver & Boecker. Vibration testing is preferably carried out as a stand-alone procedure or combined with a screening plant audit.
The vibration analysis system allows for easy “hook-up” of a tablet computer to your vibrating screen on-site by Haver & Boecker experts. The measuring system features up to eight accelerometers, allowing a full scale screen performance analysis.
{{image3-a:r-w:200}}The information allows for on-screen display of orbit plots, peak-to-peak and average accelerations and displacements, plus RPM computing and Fast Fourier Transform analysis.
Based on the data, the performance of vibrating screens can be evaluated in terms of proper speed stroke and amplitude. The determination of critical and developing faults such as bearing failures, spring problems and loose machine components is also possible.
The test results are put into a valuable and easy to understand customer report. This document not only outlines the analysed data, but also makes recommendations on how to improve screen performance based on different settings or new parts. PULSE Vibration Analysis can also provide data to implement proactive maintenance that will increase mean time between failures and reduce maintenance costs compared to the “fix it after it breaks” strategy.
The analysis will help producers better understand the interaction between feed material, screen media and vibrating screen – specific to their operation.
Source: Nepean Rubber