Modal Analysis and Operating Deflection Shape Services:

The science and art of experimental modal and ODS techniques come together to provide a picture of equipment behavior identifying faulty operation. Experimental modal analysis provides a representation of equipment performance by graphically displaying the modal frequencies (resonances) and the associated shape of each mode. The results contain not only the mode shape but quantifies performance in terms of magnitude, direction, frequency and damping. Operating deflection shape (ODS) analysis provides a similar graphical result but differs in that the analysis data is acquired during normal machine operation and does not quantify the magnitude or damping of the motion. While theoretical analysis (FEA) can provide an excellent model of behavior, it is very difficult and time consuming to create a model that exactly depicts the true operating environment whereas experimental analysis depicts actual modal response.

Experimentally derived frequency response, damping factors, and mode shapes of a structure have successfully led to:

ETS maintains an inventory of state of the art test equipment such as five different size modal hammers, multichannel spectrum analyzers, a complete array of triaxial accelerometers and a complete set of support equipment such as proximity probes, shaft sticks, laser tachs, long cabling, and accelerometer mounting systems.

A typical approach to on-site testing consists of defining the test objectives and test protocol followed by model generation, and data acquisition. Test results are viewed on site to ensure data integrity and to add immediate insight into the problem at hand (not necessarily the solution!).


Modal analysis depiction of resonance of a large fan support structure.


Model analysis depiction of a vertical solids pump with a weak adapter causing resonance

Structural modal analysis

Structural modal analysis and operating deflection shape analysis.

Modal Analysis

Vertical pump reed frequency and shaft/impeller deflection as seen in the modal analysis