technical article
Acceptance Vibration Testing: Paper Mill Vacuum Pump Nestor Enrique Niño Herrera Synapsis Ingenieria
ABSTRACT
KEYWORDS
This case history involves vibration analysis of a motor operating near its first natural frequency when installed and how it was solved. A basic model of the system was developed that predicted its behavior and led to the implemented solution. Results behaved as the expected predictions by showing a dramatic decrease of vibration levels.
resonance natural frequency phase bode coast down
bacKGRounD
A new group of three liquid ring vacuum pumps were installed in a paper mill as required by the machine upgrade. Each vacuum pump was installed on the same skid with an 1,800 rpm, 125 HP three phase induction motor by using belt transmissions. Abnormal vibration at the motors was reported during the pump running test. Dominant vibration was at 1x rpm of the motor (1,800 cpm) and out of the vibration limits established in the ISO 10816-3 standard. The vibration measured was not only high but directional, with horizontal measurements being dominant. tESt Data anD obSERVationS
It was determined that vibration at 1x (1,797 rpm) predominating in horizontal direction was in phase both inboard (1HM) and outboard (2HM) measurements points. As a system resonant condition was suspected, a coast down peak and phase test was conducted with the purpose of having the operational vibration excite the system natural frequencies and confirm resonance. A reflective tape installed on the motor shaft with an optical tachometer allowed the input reading from the shaft turning speed.
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Fig. 1: New installed vacuum pump and motor.
Winter 2019
3/22/19 12:13:39 PM