Case Study, Waste Water, Aquasystems
Underwater challenge by Aquasystems in Halle, Belgium.
Establishing the Root Cause of the Problem
After considerable time spent trying unsuccessfully to determine and mitigate the cause of a vibration issue, Aquasystems accepted that they lacked adequate in-house equipment and resource, and contracted Commtest partner, Condition Monitoring Systems bvba, to solve the problem. Condition Monitoring Systems introduced Aquasystems' engineers to the Commtest vb3000TM vibration analyzer.
The Aerator model was tested for vibration using the vb3000TM alongside complementary measurement techniques (including waveform analysis, phase measurements and bump tests). The results were outstanding, and accurately pinpointed the cause of the vibration. By connecting the vb3000TM to waterproof sensors and an underwater optical tachometer, a clear imbalance of harmonic readings was detected at specific running speeds.
Once the readings were plotted by Commtest's Ascent® software, it quickly became evident that resonance from the structural bending of the pump was the root cause of the problem. Aquasystems' engineers were elated with the results, and quickly fixed the problem by redesigning and reinforcing the housing of the modified Aquaturbo Aerator.
How the resonance problem was solved
To investigate the failure mechanism on this machine, a vb3000TM was used to gather more specific information about the vibration, together with other measurement techniques that included waveform analysis, run/up coast down measurements, phase measurements and bump testing. An additional run-out test was necessary to further analyze the problem.
With a Commtest vb3000TM analyzer connected to an optical tachometer and an accelerometer attached radial on the motor, quasi steady state amplitude and phase readings could be taken at every step. damped system (Fres = 2 Π* √k/m. m = mass, k = stiffness of the structure), it was clear that an increase in rigidity would shift the resonance frequency upwards.
Aquasystems Engineers created a new design to stiffen the pump structure with extra reinforcements. Four long strips of steel plate were cut and welded perpendicularly on the tube connecting the upper motor support with the bottom bearing support. This modification would make the structure much stiffer for the first bending mode shape.
Product Discussed
vbOnline
Flexible and modular, the vbOnline system is powered by intuitive Ascent software and permanently installed to remotely monitor the health of your critical assets 24/7, automatically alerting you to potential problems.
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