I-care Predictive Maintenance department was called to help a chemical industry with a failure detection on its assets.
I-care experts had installed six Wi-care 240 modules with a central gateway on the motor and a gearbox on an extruder in October 2019. Four sensors on the motor and twenty on the gearbox. Input/output rpm: 1383/360. The RPM is measured via an active inductive tachometer near the coupling between motor and gearbox.
The client's internal predictive personnel measured this equipment for several years, but did not found any irregularities with this installation at the time of I-care's Wi-care 240 installation. So our client was quite confident they could keep this installation running until their large turn around in September 2020.
The very first -peak hold- measurement revealed a relatively high impacting level on the coupling side of the input shaft (figure 5). This could be an indication of a problem, specific to this location.
The corresponding spectrum contained asynchronous energy at 7.59xRPM which appears to be coming from the inner ring of the FAG QJ326-N2-MPA bearing. See figure 6. Also known as the BPFI (Ball Pass Frequency Inner race).
What is more worrying, is that this BPFI energy at 7.59x RPM is clearly visible in the low frequency area of the normal vibration measurement (see figure 9). These amplitudes are highest in axial direction, measured on the input shaft – non drive end. BPFI energy visible in the low frequency area indicates the -inner ring- fault is at an advanced stage, however not so critically high further operation would be dangerous. If we hypothetically were to open and clean the bearing now, we would expect to visually see a damaged inner ring.
The customer planned on producing with this extrusion line until their scheduled stop in September 2020, but since I-care detected this problem and judged the damage quite severe, they decided the risk of producing until September 2020 was too large and planned to overhaul the gearbox during a smaller stop in January 2020.
Figures below show the damage found on the input shaft FAG QJ326-N2-MPA bearing.
To conclude this case study, we can say that the bearing damage was easily detectable in both low and high frequency measurements.
I-care experts help sealing the deal to secure the entire predictive maintenance contract for the customer.
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