A fault, in a bearing of a vibrating screen, was identified by the predictive maintenance team at Vale’s Carajás unit in Pará via Dynamox wireless sensors capable of continuously monitoring the asset’s condition.
In a mining process, this type of asset is considered critical and of vital importance, which is why predictive monitoring is so essential.
The Vibrating Screens of the Haver&Boker brand is composed of two drives, two internal and two external bearings, and has a nominal production capacity of 1400 tons per hour.
During the month of September, the monitoring system pointed out an alarm related to the evolution of vibration levels registered in the bands captured by a sensor that was installed in one of the internal bearings.
Check in the video at the end of this text some tools used to identify the root cause of the evolution of the problem.
Graphs focused on acceleration and envelope showed the evolution of the fault for specific bands and mainly at the rotational frequencies of the machine and subsequently also exciting the frequencies of the bearing, as can be seen below in the envelope cascade.
For Dynamox’s vibration specialist, Joel Nunes, the 3D graph brings very relevant information, because the analyst can work with the cascade visualization and see the spectra and envelope in the same graph, a factor that provides an indication of the failure, and can add information at the time of identification and even point out if the problem is located on the internal or external race.
Another graph used in assertive detection was the autocorrelation graph combined with the circular waveform plotting. This analysis allowed the identification of the number of impacts in each revolution of the shaft, which in this case points to the number of rolling elements of the bearing. In the video we approach the use of this tool in detail.
Through alerts generated due to the evolution of vibration and the tools used in detection, the maintenance team carried out the timely intervention before the asset went into operational failure.
During the intervention in the asset, the bearing that presented marks in the external race and rolling elements it was replaced. In addition, after disassembling the bearing it was identified that the bearing presented wear in the bearing housing.
Besides, corrosion marks that characterized an ovalization were also evidenced, factor that drastically reduces the useful life of the component. It is also noticed that the load distribution performed in the circumference of the bag and the bearing was compromised due to the irregular wear in the box circumference.
After the carried-out intervention, the predictive team performed new measurements in order to verify the levels of vibration energy and effectiveness of the intervention. According to the data collected, the components are in normal operating conditions.
Check in the video below the comparative graphics of the intervention on the equipment. The case presentation is made by our operations manager, Caroline Menegat and the vibration expert, Joel Nunes.
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