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PII employs experts in the field of machinery vibration to identify and diagnose any problems that may effect equipment functionality or reliability.  Following are some examples of the types of vibration analysis techniques in use.     

FIELD VIBRATION STUDIES

The most common type of analysis is collection of time and frequency domain (spectrum analysis) data.  This data is analyzed vs. typical average machinery amplitudes and spectral shapes to identify any impending problems.  The best possible program is trending the shape and amplitude over time for a specific piece of equipment.  Even if you don't have this kind of historical data, PII can find the evidence that will tell us the problem and allow us to devise a solution.

OPERATING DEFLECTION SHAPES (ODS)

An Operating Deflection Shape test requires the collection of transfer function data in the X, Y, and Z dimensions for all points on a simplified geometry model.  The geometry model must be designed to represent the salient features of the structure’s vibration.  A data set is collected at the steady state operating condition of interest allowing the investigator sufficient time to collect all of the required information.  Then the shapes are extracted for those frequencies having a high coherence (usually the 1X and 2X operating frequencies).

The picture to the right shows the maximum (+) and maximum (-) deflection for an electric motor bolted to its support base. Notice the flexibility shown in the support feet of the motor (triangular sections), thereby allowing the motor body deflection, while the motor support base barely moving. This information is useful in the troubleshooting phase of a problem.

EXPERIMENTAL MODAL ANALYSIS STUDIES

The experimental determination of component modal properties such as impellers and shafts are usually employed in the early design stages of a new pump.  Alternatively, in the trouble shooting phases of an existing pump installation the bearing housings and support structures are usually the focus of investigation.

The picture on the right shows a Two Nodal Diameter vibration pattern for a BFP impeller mounted on the pump shaft suspended in V blocks.  Impact excitation and dual channel signal analysis was used to collect the Frequency Response Function data set.  For each resonant frequency the mode shape and modal properties were extracted.  Each impeller on the pump shaft can have several significantly responding modes and depending on the excitation sources present during pump operation this could result in a coincidence of excitation and response frequencies, which can be destructive to the pump.  This experimental information is usually employed to fine tune the pump manufacturer’s Finite Element Analysis (FEA) programs for predicting such responses.

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