Introduction

When a large vertical motor was due for inspection it was sent by the client to a specialist motor overhaul contractor for cleaning, inspection and re-certifying.

Standard procedure by the contractor was to remove the rotor, clean and inspect and then rebuild with new bearings and seals.

After overhaul the motor was dispatched directly back to site.

Description of the machine

The motor is a 3.3kV three phase device that is used to drive a high speed single stage compressor via a speed increasing planetary gearbox assembly.

The unit is vertical with the compressor stage at the bottom, the gearbox installed above the compressor and the motor above the gearbox.

Due to fretting of the lubricated gear coupling previously used between the motor and the gearbox, I had earlier advised the plant to take the opportunity of the outage to change the coupling out to a flexible membrane type coupling.

This was done during the installation of the motor and the motor to gearbox alignment was set accurately using optical alignment equipment.