Pioneering solution waterfall spectrum for maintenance

Meet the cascade of spectrum. Dynamox is one of the world’s pioneers in providing interactive 3D web graphics for visualizing the evolution of spectral analysis data obtained by wireless vibration and temperature sensors, DynaLoggers, over a period of time.

The graphics can be rotated, dragged and zoomed, allowing a thorough inspection of the spectral evolution. Besides this, different color scales and annotations are available to facilitate predictive maintenance teams with the elaboration of fault diagnosis reports.

The spectral waterfall allows the visualization of a series of spectra from the same monitoring point, collected at different moments, on a single graph.

This tool is fundamental for observing variations in spectra over time, and could provide evidence of an emerging failure or changes in the equipment operating condition in terms of frequency ranges.

Traditionally, this type of graph is static or allows little interaction, generated in offline platforms due to the computational complexity. This means that a software or platform needs to be installed on the computer beforehand.

Furthermore, it would be required to load the data from offline collectors one by one in order to obtain the spectral measurements. In this case, the limitations of the data usage can be large, with dozens of spectra being displayed at the same time.

For online software, the spectral waterfall is commonly presented in the form of bands, with smaller spectra (< 6400 lines), or with less spectra (< 10 collections) to aid performance. There may also be limitations with respect to markers, filters and the movement of the graphic.

Dynamox has created a solution with a differential, one which allows the graphic to be generated directly on the Dynamox Web Platform on the client’s browser, using data stored on the cloud and completely online, interactive and customizable.

Graphic manipulation is also simple and fast; a waterfall can be easily moved or rotated by clicking and dragging the mouse, as found in common 3D applications.

The main challenge behind this application is to make a large number of spectra available for analysis on one waterfall at the same time.

In terms of performance, the Dynamox Web Platform can generate a waterfall for 10 spectra with 16 thousand lines each in less than 5 seconds (depending on internet connection speed). Thus, generating graphics with more spectra can take relatively longer.

Acceleration, velocity and displacement spectra are all available for viewing with high-pass, low-pass and band-pass filters to ensure diagnosis and report generation.

The graphic also features innovative markers that move with the graph and a color scheme that highlights peaks and defect bands for each collection.

Spectral trend vs Spectral waterfall

Unlike spectral trend graphs, which allow the evolution of global metrics or frequency bands to be observed, the spectral waterfall displays spectra in the same form that they are viewed in individual spectral analyses.

This makes it possible to follow all of its nuances, such as the appearance of harmonics, the evolution of a specific band, or even variations in the fundamental operating frequency of a rotating machine, for example.

Figure 1 shows an example of a spectral waterfall view. In this case, the tool can be used to identify the evolution of a bearing defect in a conveyor belt bend pulley, characterized by the resonance in the 600 – 800 Hz frequency range.

How to access the spectrum

The spectral waterfall can be accessed from the Spot Viewer (Figure 2) or Spectral Viewer (Figure 3). It is then possible to select which spectra will be displayed (Figure 4)

Configurations

Only spectra with the same configuration can be shown in the waterfall format – maximum frequency, axis monitored and duration need to be the same for each spectrum in a waterfall.

Filtering by RMS Acceleration

It is common for spectral collections to be made when a machine is turned off. As such, the field “threshold RMS acceleration” only allows spectra with vibration levels above this value in each of the available axes to be shown to the user.

Resources

Once the spectrum waterfall screen is open, several tools are available to facilitate failure diagnosis.

Interaction

The user can interact with the graphic using only the mouse. The graphic can be rotated using the left button, dragged using the right button and zoomed in and out using the scroll. In addition, the amplitude, frequency and collection date can be shown by passing the mouse over the graphic.

Spectrum Parameters

As with the spectral viewer screens, it is possible to choose which parameter to show (acceleration, velocity, displacement) in the toolbar located above the graph. On the frequency axis, spectra can be viewed in Hz or CPM and linear or logarithmic scale for improved viewing.

Low-pass, high-pass and band-pass filters

The traditional frequency filters can be applied to all of the waterfall spectra. The minimum and maximum frequency limits to be viewed are automatically updated when a filter is applied.

Annotations

Annotations can be added to an individual spectrum waterfall or to all spectra simultaneously for reporting purposes. A typical example of an annotation can be seen in Figure 6. 

Figure 6: example of annotation on a spectral waterfall

Color scale of spectrum

Different color scales are available to highlight the information transmitted by the spectral waterfall. The current version has the options to scale colors by overall maximum (a), maximum per spectrum (b), one color each (c) and all with the same color for the selected axis (d), illustrated below.

In the case of a bearing defect, for example, view (a) allows the user to identify that the maximum amplitude values are concentrated in the last spectrum waterfall of the analyzed period and are significantly larger than those at the beginning.

On the other hand, view (b) reveals that, in all of the spectra, the largest amplitudes are concentrated in the same frequency range.

The combination of these two pieces of information results in the conclusion that the same resonance zone is present in all of the spectra and evolves over time, justifying an intervention plan to prevent the bearing from breaking.

Learn more about the Dynamox Solution, as well as the products and services that Dynamox offers to help industries in predictive maintenance.

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