EXPERIMENTAL STUDY TO ANALYZE VIBRATION RESPONSE OF A ROTOR BEARING SYSTEM

Abstract

High speed rotating machines are becoming more and more common in industries each day. They have a number of components including shaft, bearings, coupler and the motor. Defects in one of these or the assembly greatly reduces the performance of the system and increases the power requirement for same output. All rotary machines vibrate while operating, but the vibration in a system with defects is very different form a system without defects in terms of amplitude as well as frequencies. So, a comparison of vibration signature with and without defects can help us relate the cause. of the vibration to the effect observed. This cause effect relationship can help us a lot in diagnostics and prognostics of the machinery. An experimental set-up has been designed and fabricated to study the vibration response of typical high speed rotary machines, for speeds up-to 10000rpm, under varying conditions. The set-up has a shaft, supported on two rolling element bearings, driven by an electric motor connected through star coupling. The entire set-up rests on a concrete foundation. Piezoelectric sensors have been fixed on the bearing blocks to obtain the vibration response of the system under dynamic condition. These sensors are connected to a portable vibration analyzer which plots time domain vibration response as well the frequency domain response of the system. The Capabilities of the set-up include the variation of shaft length, flexibility in the amount of imbalance the can be introduced, flexibility in selection of bearing-and shaft diameter etc. Also, the motor in the set-up can easily be replaced by variable speed drive, or other motors to offer flexibility of speed.