ORBIT ANALYSIS

Orbit analysis is a necessary tool for vibration analysis of rotating machinery. The process is essentially an extension of time waveform analysis plotting time-domain data from a pair of orthogonal probes on an orbit graph with consideration for the physical location of the proximity probes.

Setup

In the channel setup section of the orbit analysis plugin different measurement parameters are set through a designated user interface. The settings are divided into four major sections:

  • Frequency channel setup
  • RPM Setup
  • Calculation Setup
  • Machine configuration

Frequency channel setup

Under frequency channel section of setup, frequency source is selected and the correct sensor is configured.

Frequency source: Counters, Analog pulses, RPM channel

Sensor: Tacho, Encoder, CDM, Geartooth, X-n sensors

Frequency channel: input channel with connected tacho/counter sensor

RPM setup

Under RPM setup section, lower and upper limits are defined as well as Delta RPM and the direction of the test.

Direction: Both, Runup, Coastdown

Delta RPM: user inputs the desired value, the lower the value the higher the resolution and more CPU power needed.

Upper & Lower RPM limit: user inputs desired values, they corresond to the values of the tested rotor.

Calculation setup

Calculation parameters are set up under the following section, such as: list of desired harmonics, type of FFT window, resolution and update settings.

Harmonic list: input desired harmonics for calculation (e.g. 0, 1, 2)

Order resolution: 1, 1/2 , 1/4 , 1/8 , 1/16, 1/32, 1/64

FFT window: Blackman, Rectangular, Hanning, Hamming, Flat top, Triangle

Update interval: user inputs desired values. Buffer duration is calculated according to the input value and is displayed as an output message in orange on top of the ch. setup screen.

Order waterfall: select the desired checkbox to output either order vs. RPM, FFT vs. time or both as waterfall.

Machine configuration

Machine configuration setup can be further broken down into for subsections:

1 - Quick settings: Pair/Mono, CW/CWW, input ch., Angle, Position

2 - Measure: measure DC gap button

3 - Setup: opens additional settings for the bearing, further explained below under Bearing setup

Bearing setup

When selecting Setup subsection, a pop up dialogue appears with advanced bearing setup options.

1 - Sensors: configure proximity probes and tacho position & angle.

2 - Runout compensation:: input runout compensation data into the designated table or simply paste it from elsewhere.

3 - Measurement: set shaft rotation direction, clearance circle size and shape, number of periods and averages taken into the average orbit calculation or manually input DC Gap.

Component name is a user input field for bearing name.

Measurement

Orbit analysis comes with a set of designated widgets needed for precise analysis and representation of results. These widgets can easily be configured to show standard parameter combinations used in orbit analysis. Different standard displays are further elaborated in the following section.

As with any other Dewesoft module, additional inputs can be easily added and shown on the same or different display. Below is an example of predefined Orbit Analysis display.

Order analysis widgets

Below is a list of typical displays used in orbit analysis that can easily be created using predefined display widgets within Dewesoft Orbit Analysis.

Raw orbit with clearance circle

Raw orbit is seen in orange on the graph with clearance circle in red.

X and Y mark the position of proximity probes, whereas T marks the tacho’s position.

Rotation direction is also shown on the graph with an arrow.

Shaft centerline

Shows shaft centerline movement in white vs. RPM inside the clearance circle.

Full motion graph

Full motion graph consists shows Shaft centerline, Clearance circle and Raw orbit on the same display widget.

Average orbit with clearance circle

Average orbit is seen in turquoise on the graph with clearance circle in blue.

X and Y mark the position of proximity probes, whereas T marks the tacho’s position.

Rotation direction is also shown on the graph with an arrow.

Nx/Filtered orbit

Above display widget shows example of filtered orbits in white, turquoise and orange. The particular orbits shown are: X(White), 2X(Orange) and 3X(Turquoise).

Polar plot

A single display in polar plane displaying phase and amplitude(displacement) at certain RPMs.

Bode plot

Display widget for complex channel with different available data to display: Phase, amplitude

Waterfall

Both order vs. RPM and FFT vs. time waterfalls are supported. Above image shows and example display of order waterfall vs. RPM with added digital display for speed.