Averia excentricidad test motors

Project details

  • Date

     20/04/2017

INTRODUCTION

Test Motors, through its tool of predictive maintenance TestIM, allows to detect faults of the engine or of a component, in this case of a compressor of which the motor is in cantilever. It is a 430 Kw compressor driven by a static starter.

FAULT DETECTION

During the last months of motor operation, the bearing temperatures on the opposite side of the drive increase. The customer decides to install our TestIM SmartSoft fault detection system, and we started monitoring the machine at the beginning of the year.


As of March 7, vibrations of the engine increase from values ​​of 3 mm/s to 16 mm/s, on March 12 for vibrations on the horizontal axis, and even much higher values ​​on the vertical axis. (Limit of ISO10816 is 7.1 mm / s, for machines with rigid support). The TestIM SmartSoft system locates the source of the vibration, in the motor shaft, part 8, which can be dynamic/static unbalance/eccentricity of the machine.

By analyzing the magnetic flux generated by the machine this fault is confirmed and a significant increase of the frequencies characteristic of this mode of failure is detected.

GRAFICA EXCENTRICIDAD

 

 

MOTOR STATUS

 

The system displays the fault indication on the "Motor Status" screen.

Causes of the fault

The actual mounting of the motor, with flange, for such large powers, we believe is not recommended. Fatigue and sudden variations in temperature can cause dilations/contractions in the machine that alter the concentricity of the rotor relative to the stator. Providing increased vibration of the machine. In addition, the cantilever assembly clearly assists in the presence of imbalance in the machine. Alteration, which has also been detected, but less intense.

EXCENTRICIDADES

Confirmation of the fault

To confirm the fault and due to the impacts that were observed the first days of generation of the fault, it is recommended to open the motor and to observe in the stator and rotor the wear of the lamination.

 

ROTOR DESGASTADO

Detail of a rotor brushed by the stator

CORRECTIVE ACTION
The customer decides to replace the motor with one that has the sound rotor, and a base is installed that prevents the motor shaft from being deflected. It is recommended to eliminate this fault by means of an assembly with motor feet, on the opposite side of the drive (NDE), which also allows correct alignment with the load. In this way fatigue would not affect the concentricity of the machine.

Accion correctora excentricidad