Order Analysis
In rotating and reciprocating machines, varying load conditions and imperfections of the moving parts cause vibrations and associated sounds. The vibrations are shaped by the structural properties of the moving and stationary parts of the machine. Relating spectra and time histories to the RPM of the rotating parts, Order Analysis is the tool that reveals the vibration and sound mechanisms:
- Critical speeds
- Excited resonances (weaknesses)
- Instabilities
- Varying load
Brüel & Kjær offers a comprehensive selection of Order Analysis methods:
- Order Analysis, based on frequency spectra, FFT
- Order Analysis, based on order spectra, tracking
These methods, operating in real-time, provide spectra (waterfall, colour contour), individual order and structural slices versus RPM of one or more rotating parts.
- Vold-Kalman Order Tracking Filter
Based on captured time histories, this method extracts individual orders in terms of magnitude and phase; PAS or wave signal versus one or more RPM.
All methods support use of multiple tacho signals and voltage/RPM signals as references, and with the Autotracking™ functionality it is possible to extract the tacho signal directly from a measurement input, for example, in cases, where a tacho signal is not directly available. Dependent on configuration, related analysis are provided:
- 1/n-octave spectra versus RPM
- Weighted sound pressure level versus RPM
- Speed profile, RPM versus time
With PULSE Auxiliary Parameter Logging all data can be tagged with temperature, oil pressure, position, wind speed, etc., and all results can be shown versus auxiliary parameters.
Order Analysis Type 7702
Type 7702 provides PULSE, the Multi-analyzer System Type 3560 with tachometers and order analyzers, and related post-processing functions, as well as additional trigger types. The software includes PULSE Application Projects that cover the main uses of Type 7702. The system can be easily customised to suit other measurement tasks. Uses include:
- Separation of rotational and structural noise and vibration phenomena
- Identification of noise generated by rotational vibrations
- Determination of critical speeds and resonances
- Investigation of instabilities in rotating machinery
Vold-Kalman Order Tracking Filter Type 7703
Type 7703 allows high-performance tracking of harmonic responses, or orders, of periodic loads in mechanical and acoustical systems. This method allows the beat-free extraction of close and crossing orders in systems with multiple axles, and possesses a finer frequency and order resolution than conventional techniques. The tracking capabilities are independent of the rate of change of the rotational speed (slew rate).
