this about vertical pump which tripped due to high vibration. Pump speed 745 rpm. During the cost down the vibration cascaded spectrum was at 740 cpm at every speed till zero. What does this indicate ??? Is natural freq or something else.
Are you saying the pump in question was shut off and you monitored the vibration amplitude and frequency while coasting down and the vibration stayed at 740 cpm on the problem pump all the way until it stopped? Is motor controlled by variable speed drive?
Then you uncoupled the motor and the vibration started at 5 then increased to 10. Was the speed changed when vibration increased or did vibration increase while at full speed?