Our customer informed us about failure of cage motor, that was recently repaired in our workshop (630 kW, 6 kV, 50 Hz, 1500 rpm, TEFC). D-end bearing failure happened after ca. 6 weeks of continuous motor operation and – since the user did not apply remote vibration- nor temperature monitoring (although Pt100 sensors are installed in the bearings) – it led to complete destruction of the bearing and adjacent parts, heavy damage of the shaft as well as seizure the rotor and stator cores.
Our client uses motors of this type (all ca. 20 years in operation), driving 3 blowers; two of them are coupled with the motor by means of shot-type coupling, one – by standard ‘rigid’ coupling. It was fourth identical failure (in respect of its course and consequences) of successive 4 motors during last 6 months. Prior to installation, these motors were inspected/repaired by different companies (all with long experience in service of el.machines). What is (in my opinion) important, all of the failures happened on the motors coupled by shot coupling. It seems to me, that the primary reason of the failures is operational problem of the shot couplings – but I have very little experience with this type of couplings (by the way, I don’t see the reason for using shot coupling in these drives, considering that motor&blower with standard coupling work without problems).
Is it possible, that after many years of operation, wear processes in the shot coupling could cause eg. rapidly occurred imbalance condition, leading to severe vibration and quick destruction of motor’s bearings? The user asserts, that the couplings are periodically inspected, but…
I would appreciate any help/suggestions in this matter.
Thanks in advance.
Our client uses motors of this type (all ca. 20 years in operation), driving 3 blowers; two of them are coupled with the motor by means of shot-type coupling, one – by standard ‘rigid’ coupling. It was fourth identical failure (in respect of its course and consequences) of successive 4 motors during last 6 months. Prior to installation, these motors were inspected/repaired by different companies (all with long experience in service of el.machines). What is (in my opinion) important, all of the failures happened on the motors coupled by shot coupling. It seems to me, that the primary reason of the failures is operational problem of the shot couplings – but I have very little experience with this type of couplings (by the way, I don’t see the reason for using shot coupling in these drives, considering that motor&blower with standard coupling work without problems).
Is it possible, that after many years of operation, wear processes in the shot coupling could cause eg. rapidly occurred imbalance condition, leading to severe vibration and quick destruction of motor’s bearings? The user asserts, that the couplings are periodically inspected, but…
I would appreciate any help/suggestions in this matter.
Thanks in advance.
