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Misalignment Detection Using Operational Shape Deflection

Lin Liu & Suri Ganeriwala
SpectraQuest Inc., 8227 Hermitage Road, Richmond, VA 23228
Published: October, 01 2005


Misaligned rotating machinery is causing high cost to industry due to prematurely damaged machinery, lost production and excessive energy consumption. Therefore, a robust, accurate and convenient misalignment detection technique is needed. This work investigated the perspective of using operational deflection shape (ODS) to check the machinery alignment condition. It is expected the relative motion (amplitude and phase) among different components of machine, especially the components connected with the shaft, will be affected by misalignment. This work focuses on the influence of misalignment on the motion of machine during one rotation of the shaft. Two types of misalignment are studies, i.e., angular and parallel misalignments. The results suggest that ODS is a potential method to detect misalignment.

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The test is performed on a Machinery Fault SimulatorTM (MFS) made by SpectraQuest. Three tri-axial accelerometers are mounted on the MFS. The coupling is a rigid Ruland coupling. The nine channels acceleration data is collected simultaneously using a VibraQuest hardware/software system.

The acceleration data is exported to a ME'scope model to visualize the ODS of the machine and to determine the effect of misalignment on ODS.

Misalignment introduces synchronous force to the machine structure. It a three dimensional force and produces several harmonics of the running speed. In order to see the effect of misalignment on ODS, it is important to separate non-synchronous vibration from the synchronous components. The term synchronous is used to describe vibration at and the harmonics of the running speed. All other components are considered non-synchronous vibration.

The raw data is processed in ME'scope data block window to have the noise and other non-synchronized signal removed. Ten shaft harmonics data is extracted and used in the ODS animation. The ODS is animated in the time domain for the period of one shaft rotation.

Fig. 1: Machinery Fault Simulator