Piping Analysis in Industrial Process and Power Generation Applications; a view into how our analyzers can be applied
In this article we examine virtually every aspect of rotating machinery analysis for systems used in industrial processes and power generation applications may be tackled effortlessly using SignalCalc Dynamic Signal Analyzers. Rotating machineries comes in various sizes, configurations, speed ranges, etc., but all are susceptible to vibration and if unchecked, this vibration can lead to catastrophic consequences.
Basic RPM based processing and Order Analysis
Any SignalCalc Dynamic Signal Analyzer is a remarkable tool with just the most basic time and frequency domain measurement capabilities. Add to these the ability to measure RPM from either a single or multi pulse per rev tachometer and you have an instrument with a virtually unlimited set of applications. This option uses the tachometer input of your system to measure machine speed concurrently with the normal acquisition of measurement signals. The Trigger front panel connections accept a periodic analog or TTL signal from a tachometer probe or shaft encoder monitoring the machine under test. The tachometer circuits trigger on this waveform to produce a conditioned pulse train with one or more pulses per revolution (PPR); the frequency of this pulse train is proportional to the machine’s shaft speed. In the example shown below, vibration data from a turbocharger run up and run down test is presented in a waterfall plot. The RPM axis shows the speed range for the test and order cursors conveniently relate measured vibration frequencies to multiples of the turbocharger shaft rotational frequency.
Advanced Order Tracking
SignalCalc analyzers offer advanced order analysis capabilities using either high performance tracking filters or through digital resampling. In the case of the latter, the analyzer synchronizes the sampling of input signals to the instantaneous angular position of the machine’s shaft. Rather than sampling a constant number of times per second, a constant number of samples per revolution are acquired. The technique allows modern dynamic signal analyzers using Sigma Delta ADCs that do not lend themselves to be driven by an external clock derived from a rotating machine, to still deliver high resolution order analysis over the machine speed range. This analysis provides revolution histories and order spectra.
The figure below shows the same turbocharger run up and run down test data processed using digital resampling based order tracking; the result is a color spectrogram with high resolution order spectra.
Synchronous averaging involves triggering the data acquisition by the analyzer using an external event, such as a 1/rev tachometer pulse, and performing linear averaging on the acquired data. Using this technique, users can determine the contribution of vibration to the overall, from multiple rotating components. The figure below shows a unique method of presenting time synchronous average data: a polar runout plot, where the time average data for one shaft revolution is shown in a 0-360 º circular format. The data resolution allows the user to see the contribution of the shaft coupling with the gear mesh frequency of the driving gear also clearly visible.
The SignalCalc analyzer family, using Hilbert transform based demodulation, performs Envelope analysis and more generally, both Amplitude and Phase/Frequency Demodulation. Useful for analysis of bearings, gears and drive speed variations, this tool may also be combined with synchronous averaging as discussed above to lock the analysis to a particular rotating shaft of interest.
Rotor Dynamics Analysis
SignalCalc Turbo is a portable data acquisition and analysis system for rotating machinery analysis, designed specifically for turbomachinery test users analyzing machines with journal or fluid film bearings. A comprehensive measurement suite offering both vector and waveform based sampling, automatic tachometer triggering and high voltage inputs for proximity probes combined with effective display and analysis tools makes this elegant and easy to use software package the ultimate solution for field engineers requiring mobility and flexibility.