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As vibration isolation and reduction techniques have become an integral part of machine design,the need for accurate measurement and analysis of mechanical vibration has grown.
recommended vibration monitoring fo shaft speed / phase reference a keyphasor transducer should be supplied on each independent (non-mechanically coupled) shaft to provide a once-perturn reference signal for determining vibration phase and shaft rotative speed. It is generally recommended that the Keyphasor transducer be installed on the driver in a machine train, so that if the unit is run uncoupled, a phase reference signal will still be available. This is not possible when a Keyphasor transducer is only installed on the driven machine.
when frequency analyzing machine vibrations we normally find a number of prominent periodic frequency components which are directly related to the fundamental movements of various parts of the machine. With frequency analysis we are therefore able to track down the source of undesirable vibration.
In case of misalignment & bent shaft frequency of dominant vibration (Hz=rpm/60) Usually 1 x rpm often 2 x rpm Sometimes 3 & 4 x rpm