Resolving High Vibration On a Vertical Pump
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Turbomachinery Laboratory, Texas A&M Engineering Experiment Station
Abstract
There is a single stage vertical pump installed in Acetic Acid area in a petrochemical plant. The unit is vertical high
pressure (HP) reactor feed pump (High speed single stage, 230 kW, 12338 rpm & 3.444 gear ratio) driven by induction
motor through a flexible shim pack coupling.
High vibration levels were observed on the motor, pump and structure for more than 2 years with 1X dominant
vibration (1X motor dominant frequency). Assuming that the issue is completely structural as this motor was running
well in the past, there were some structural modifications have been carried out at site with inadequate engineering
calculations. The modifications were welding a total mass of 100 kg onto the structure and the installation of braces
to the structure which did not yield any positive results. A systematic structural measurement along with the
Operating Deflection Shape carried out at site with the help of experts did not reveal a significant issue with the
structure itself except for the structural natural frequency being slightly closer to the running frequency of the motor.
The timely right decision by the experts to carry out an onsite balancing on the motor, which was intended to remove
the excitation force, yielded good results which exposed a mistake in the balancing activities carried out by a local
vendor at work shop.
This case study is designed to outline how the high vibration issue was successfully diagnosed using various tests on
site including the operating deflection shape, the root cause for the high vibration and finally how it was mitigated.
Description
Case Studies