Detection of a fault in a turbine by disuse

Project details:

Date:
20/04/2017

INTRODUCTION

Test Motors, through its predictive maintenance tool TestIM, allows to detect when the life of a component, in this case the one of the bearing of a turbine-compressor of a client of the chemical sector, has been terminated, and it allows to know when its substitution. It is a turbine-compressor driven by a 250 kW squirrel cage rotor induction motor that is started to be monitored at the end of 2015.

FAULT DETECTION

From April to July 2016, the motor remains stationary, and when restarting, between the end of July and August, (see the attached chart) the system detects an increase in the vibrations on the side of the turbine. When looking at the graphs, and analyzing the typical fault frequencies, it is observed that the increase of vibrations is due to a fault in a bearing of the turbine.

Causes of the fault

The reason for this failure is due to the fact that the machine has stopped for several months, and this has generated a "maintenance" defect in the bearing assembly. It is a machine of little use, and failing to perform the optimum operating conditions for which it has been designed, the components have ended up failing.

The graphs show us the increase of the vibrations during the development of the fault, and how they decrease when performing the replacement of the bearing.

CORRECTIVE ACTION

After commenting with the customer, it is decided to replace the bearing on the side of the turbine, and subsequently a decrease of the vibrations of the turbine is observed. To verify that the action performed has been correct, we observe in the attached graph, that the RMS vibration values return to their normal state, and the critical bearing frequency decreases.