For more information about Order tracking take a look at the Order tracking manual.
Dewesoft order tracking method is used to extract the harmonic components related to a rotational frequency of the machine. With order extraction, we can see a specific harmonic component which relates to certain machine fault.
The mechanical vibration pattern is a mixture of excitation frequencies, usually related to rotational speed, such as unbalance, eccentricity, bearing faults and other and machine response function, which relates to machine natural frequencies based on the structure and mounting of that machine.
Machine vibration pattern - is a mixture of excitation frequencies, usually related to rotational speed, such as unbalance, eccentricity, bearing faults and other machine response functions, which relate to machine natural frequencies based on the structure and mounting of that machine.
Harmonic component - which relates to certain machine fault: - the first order (harmonic) usually relates to unbalance of the machine - the second harmonic often relates to eccentricity - if we have for example 9 rotor blades, 9th harmonic relates to errors on the blades - if we have for example 31 teeth on the gear, then the 31st harmonic will show the gear mesh frequency…
Final measured vibration - The ratio between excitation and system response is defined by the system transfer curve. So the final measured vibration of the system is a product of excitation force and system transfer curve. Since the transfer curve is fixed, we get different responses for excitations at different rotation speeds. When the excitation passes natural frequency, we get so-called resonance with increased vibration amplitudes which could be fatal to the machine.
NOTE: To measure Order tracking, we need at least one accelerometer for measuring the vibration and angle sensor for measuring RPM.
- Required hardware - Sirius, Dewe 43
- Required software - SE or higher + ORDTR option, DSA or EE
- Setup sample rate - At least 10 kHz
Add / New Order tracking module
For instructions on how to Add new module see -> Setup -> Add module.
When an order tracking module is added, we get the following window with the settings for order tracking.
This screen has the following main sections:
- Input channel selection
- Output channel settings
- Frequency channel setup
- Calculation criteria - frequency limits
- Order FFT setup
- Common properties
- Time FFT setup
Frequency channel settings
There are several possible sources of the frequency which can be selected from Frequency source drop-down list:
We can have the frequency source as Counters. In this case, the angle sensor should be an encoder or gear tooth. Then we select the sensor itself from Sensor drop-down list and the source where this sensor is connected to.
If we choose the encoder, then we need to connect the encoder to the counter input.
By selected encoder on this section, we have two additional settings. Input Filter defines the digital filter of the data to prevent double triggers (same function as in counters).
The second option is to select the Analog pulses as the source. In this case, the sensor should be connected to an analog input and the angle sensor math is used for getting the angle and the trigger from analog data. Please be careful that the sample rate is high enough to catch the pulses also at high frequencies.
Define the trigger levels by pressing the ” … ” button which appears on the left side of the Frequency channel field.
When the ” … ” button (on the right of Sensor field) is selected, we get Counter sensor editor window where angle sensor should be defined. see -> Counter sensor editor.
The third option is the RPM channel. In this case, the frequency source comes directly from an analog channel which measures the frequency.
The fourth option - Torsional vibration is available when we have torsional vibration. The source can come directly from torsional vibration.
Calculation criteria - frequency limits
In this section we need to define the lower (Lower RPM limit) and upper (Upper RPM limit) rotation speed which we would like to see and the difference (Delta RPM) in rotation speed. These three parameters are important for reserving memory of waterfall FFT based on the order tracking.
We can also define the Direction of triggering either to capture only Run-up, Coast-down or Both. This criterion will tell the order tracking module when to take the measurements.
Here can we also Skip missed RPMs with checking this box.
Order FFT setup
In this section, we define the order history FFT properties, but also the properties for order extraction.
First, we define the Order resolution, which reflects also the minimum number of revolutions acquired for a single calculation. If we set 1/16 order for the resolution, we need to acquire at least 16 cycles for a single data point.
The Maximum order defines how many orders (harmonics) we will get and can be selected from the drop-down list.
This value and the maximum RPM defines the sample rate needed for acquisition. If the sample rate is not high enough, this will be written as the error message in the caption.
Order extraction setup - We will see all the orders in the history FFT, but if we want to draw the Bode or Nyquist run-up plots (in the x-y recorder), we need to have the data available as the channels. In this section, we define the orders (or harmonics) which will be available as channels From the list (see right) or All.
If we have the frequency source with a reference point (tacho or encoder), we can also get the phase, real and imaginary component of each harmonic.
We set (select from drop-down list) the FFT window type for calculation of the history FFT.
In this section, we define the time Update criteria from the drop-down list for taking new samples. We can define to acquire the data Only at first time Run-up / Coast-down or Always when passing through some frequencies.
We can also define the Maximum time limit. If the frequency doesn’t change within a specific time, we will still get another point for harmonics and 3D history.
Time FFT setup
- Time domain harmonics - This creates a complex output channel showing the amplitude of harmonics in a time domain. In the harmonics list section, we define the harmonics that we want to extract. FFT waterfall vs. RPM - he resolution of the FFT waterfall vs. RPM can be defined by the number of lines (delta frequency is also shown). It can be also set to Auto - the resolution is calculated from the max. order, sample rate, and order FFT size.
- Update on RPM change (Delta RPM) - Delta RPM will define when a new update of the waterfall spectrum and also the extracted order domain harmonics are calculated.
- Update on - In case, the RPM is not changing only channels from Time FFT setup can be calculated according to the maximum time limit setting.
- Overall RMS vs. RPM - This option will create a channel that shows the overall RMS amplitude over the range of RPMs
Output channels settings
The lower-left area displays the output channel settings with fields like in the analog channel setup: Name, Units, Color, Minimum value and Maximum value, also a symbolic display of signal values.
For help with Output Channel list see -> Setup -> Output Channel list.
Order tracking can have more output channels according to the selection of Output extracted harmonics as channels.