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Bearing envelope analysisVibration analysis to detect and diagnose faults in bearings and gears

The Dewesoft Envelope Analysis solution combines top-tier data acquisition units with powerful software, offering an easy-to-use interface and quick configuration. It includes an integrated recorder, a comprehensive bearing database, customizable envelope settings, and adjustable signal bandwidth. For convenience, predefined bandwidth settings (Envelope 1-4) are also available, providing a cost-effective and efficient solution for bearing envelope analysis.

Bearing envelope analysis highlights

Dewesoft quality and 7-year warranty

Enjoy our industry-leading 7-year warranty. Our data acquisition systems are made in Europe, utilizing only the highest build quality standards. We offer free and customer-focused technical support. Your investment into the Dewesoft solutions is protected for years ahead.

Software included

Every Dewesoft data acquisition system is bundled with award-winning DewesoftX data acquisition software. The software is easy to use but very rich and deep in functionality. All software updates are free forever with no hidden licensing or yearly maintenance fees.

Bearing analysis introduction

In manufacturing or processing plants with rotating equipment, bearing failures are the most common machine fault. Vibration analysis is essential for diagnosing these issues, as it helps with condition monitoring and fault detection of rolling element bearings. Bearing Envelope Analysis (BEA) identifies and diagnoses bearing faults by extracting periodic impacts from a machine’s vibration signals.

Dewesoft’s Envelope Analysis provides a cost-effective solution by combining high-quality data acquisition units with powerful software. It offers an easy-to-use interface, fast configuration, and includes features like a recorder, bearing database, customizable envelope settings, adjustable signal bandwidth, and predefined bandwidth options (Envelope 1-4).

Envelope detection

Envelope detection is a signal processing technique used primarily in vibration analysis to detect and diagnose faults in rotating machinery, such as bearings and gears. It is also used to detect and diagnose faults in roller bearings.

It works by extracting the modulating signal (or envelope) from high-frequency vibration data. This helps to isolate and identify repetitive, impact-like events, such as those caused by a defect in a bearing or gear.

When bearing elements strike a local fault, an impact is generated. These impacts occur at different repeating frequencies, depending on the bearing’s geometry and rotational speed. The repetition rates, or bearing frequencies, are unique to each type of bearing and are calculated using specific mathematical formulas.​⬤

The impacts modulate the signal at specific bearing pass frequencies, including:

  • Cage Pass Frequency (CPF)

  • Ball Pass Frequency Outer Race (BPFO)

  • Ball Pass Frequency Inner Race (BPFI)

  • Ball Fault Frequency (BFF)

These frequencies are associated with the unique characteristics of the bearing’s operation.

Envelope Analysis is based on the FFT (Fast Fourier Transform) frequency spectrum of the modulating signal. When the original signal is amplitude-modulated, envelope analysis extracts the modulating signal through amplitude demodulation. The result is the time history of the modulating signal, which can either:

  • Be studied directly in the time domain

  • Be further analyzed in the frequency domain

This process allows for detailed insight into the behavior of the signal. Dewesoft offers advanced solution for envelope detection. Check our envelope detection SW manual for details.

Supported sensors

Dewesoft data acquisition support a wide range of industry-standard accelerometers including those with differential voltage, IEPE, and charge outputs. Our patented DualCoreADC® technology allows for the measurement of a broad range of signal amplitudes without needing to switch between ranges. Additionally, with an extra counter per channel (ACC+), you can measure both vibration and RPM in full synchronization, all in a compact format.

Key features:

  • Connector type: BNC, DB9 or LEMO connectors

  • Input options: Voltage, IEPE, Charge

  • Supported sensors: Single or multi-axial accelerometers

  • Speed and RPM acquisition options: Tacho, tape sensor, encoder, geartooth, or any RPM sensor with a 5V TTL signal output

  • Speed and RPM acquisition inputs: Counter, Analog in with Angle Math

This setup ensures versatile and accurate measurements for a variety of applications.

Additionally, our DAQ systems provide support for TEDS sensors, making sensor connection and configuration plug-and-play.

Applications of Envelope Analysis

Envelope analysis is widely used in industries that rely on rotating machinery, such as:

  • Paper manufacturing

  • Chemical processing

  • Textile production

  • Power generation

  • Mining

  • Steel production

Key uses include:

  • Non-intrusive monitoring of roller bearing health

  • Identification of cracks in both the inner and outer races of bearings

  • Detection of roller defects, wear, and poor lubrication

This technique provides crucial insights for maintaining and diagnosing the condition of rotating equipment.

Bearing and gear analysis

Envelope acceleration is a powerful technique used to demodulate high-frequency acceleration spikes into characteristic frequencies associated with bearing faults and gear mesh patterns. This allows for the detection of faults such as cracks, wear, and misalignments within rotating machinery components.

Dewesoft’s software includes a comprehensive bearing database that contains a wide range of bearing models, making it easy to analyze specific bearings. The database is fully customizable, allowing users to add new bearings as needed, ensuring flexibility for different applications.

The software automatically identifies critical frequencies in the spectrum, such as inner and outer race defects, cage pass frequencies, and gear mesh frequencies. These frequencies are highlighted for each part of the bearing or gear system, making it easier to pinpoint potential issues and ensure timely maintenance.

This advanced diagnostic capability helps improve machine reliability, reduce downtime, and extend the life of rotating components.

Bearing Fault Detection With Envelope Detection

Envelope detection is a standard procedure for the early detection of faults on ball bearings.

When a failure of the ball bearing occurs, it will produce ringing with a frequency that corresponds to its natural frequency. This ringing will repeat each time when a damaged part of the ball hits the ring or vice versa. In addition, the inner ring, outer ring, cage, and balls have different typical repeating frequencies depending on the geometry of the bearing and the rotational frequency. 

With DewesoftX data for bearing components are automatically managed by a bearing database. Using envelope detection and the bearing database simplifies pin-pointing critical frequency components related to specific bearing components and enables kinematic cursors to be used. 

Download Bearing Envelope Analysis brochure​​​​​​​.

Envelope Detection - Energy and Peak Available

The envelope detection algorithm is highly configurable and offers several key features:

  • No limit on high-pass filter frequency: Ideal for low-speed rotating machinery, especially when used with the Dewesoft ASI-1xVIB acceleration sensor, which has a flat frequency response from 0 Hz to 10 kHz.

  • Energy and peak detection: Both RMS and PEAK values can be calculated, with RMS representing the energy of the spikes, and PEAK capturing the maximum spike value.

The envelope signal can be visualized in various plot types, including:

  • Time waveform

  • Frequency spectrum (with Hz or RPM on the horizontal axis)

  • Order spectrum

This version improves readability with clear structure and highlights key points effectively.

FFT analysis (Fast Fourier transform)

FFT analyzer module provides all functions for spectral analysis with advanced averaging, selectable resolution (up to 64000 lines), or direct specification of the bandwidth (0.01 Hz). Multiple channels can be displayed in the same FFT visual display for easier comparison. FFT features:

  • Multiple cursors and markers: provide easy access to marked frequency values. Free, RMS, Max, Sideband, Harmonic, and Damping markers are available. 

  • Bearing cursor: used to identify the bearing frequencies

  • Envelope: envelope detection is a procedure for the early detection of faults on ball bearings

  • Auto and cross-correlation

  • Cepstrum

  • Short time FFT

Cursors and Markers Multipurpose Frequency Cursor Functions

The Dewesoft FFT analyzer allows setting multiple processing markers for automatic detection of different parameters. Our frequency analyzer offers the following markers:

  • Free marker: Free markers can be freely added. The marker shows us the axis position and the amplitude of the selected graph location.

  • Maximum marker: The maximum marker finds the highest amplitude in the spectrum.

  • RMS marker: RMS markers will sum up all the FFT lines in the selected band and calculate the RMS value.

  • Sideband marker: The sideband marker monitors the modulated frequencies to the left and right from the selected centerline.

  • Harmonic marker: Shows harmonics of the fundamental frequency, and can be used to investigate signal distortion and non-linearities. 

  • Damping marker: Damping markers are best to use in modal testing when we want to find out how our transfer curve is damped. We select it when we are interested in the quality factor, damping ratio, or attenuation rate of a selected peak.

  • Delta marker: shows the difference in channel values between two positions of the marker.

  • Kinematic marker: Advanced envelope detection is used to identify bearing frequencies and bearing faults. Kinematic markers simplify fault detection during measurement. Create your own bearing sets in the database. 

  • Zoom marker: Easily zoom in the selected region of the channel(s).

  • Vector cut marker: Outputs a user-defined region of a spectrum as a new channel.

  • Trigger marker: Outputs 0 or 1 depending on if the user-defined trigger level is exceeded by the related signal.

All processing markers work as derived math channels and will create new channels that can be stored and used for additional analysis.

Kinematic markers

Kinematic markers are used to identify the bearing frequencies and bearing faults. DewesoftX software offers a convenient way to add a new bearing go to the Kinematic cursor editor.

Each bearing database includes bearing data (what is the base of the component (cage, rolling element, outer race, and inner race) at 1 Hz and at which frequency has the component a peak in the frequency domain).

Kinematics marker properties:

  • Current value: Displays only the current value of the marker and can be interacted with while storing.

  • Full history: Stores calculated values in output channels and can be used as input in other modules.

  • Snap to data points: If selected, the marker’s position will snap to the FFT bin; otherwise, the marker can be placed at any frequency, with the value interpolated at that exact frequency.

  • Find peak in region: If selected, the marker will automatically search for the peak within the selected frequency band centered on the marker’s position.

  • Improve peak accuracy: If selected, the peak position and value are interpolated from the FFT data.

  • Kinematic cursor: Assign the appropriate marker from the Kinematic Cursor Editor.

  • Position source: The position source has two modes—Widget marker and Channel. If the widget marker is selected, the position is defined manually. In Channel mode, the position is defined by the current value of the selected channel.

  • Frequency of rotation: Determines the position of the kinematic markers. The frequency must be input manually and can be defined in Hz or RPM.

After setting up, user can see kinematic markers at frequencies defined in the kinematic cursor database. The table will also show which mechanical part each frequency is related to.

Kinematic markers can also be visible on the DewesoftX 3D graph.

Cross-spectrum and Auto Spectrum

The typically used results from FFT analysis are the Power spectra (Autospectra) determined from single individual input channels. If characteristics across multiple channels are required for analysis of correlation and phase relations, then cross power spectra are used.

With cross-spectra a reference channel is selected and cross-spectra is calculated for all channels relative to that reference channel.

Order Tracking Analysis

The order tracking module makes it extremely easy to take time-domain data and transform it into the angular (order) domain. It can extract any number of harmonics (amplitude and phase angles) which can be displayed in Bode, Nyquist, 3D FFT, real-time x-y, and orbit plot. The plane view FFT clearly shows the excitation forces, natural frequencies, and all the resonances to give a clear picture of the dynamic behavior of the machine.

Any input can be used: microphone, accelerometer, and even the output of the torsional vibration module (see below). The patented digital counters technology (Supercounter®) provides very accurate and repeatable measurements. Results are represented on a 3D color spectrogram and 2D graph for selected order and phase extraction over RPM.

Learn more about Order Tracking analysis:

  • Order Tracking Analysis solution page

  • Order Tracking online PRO training course

  • Order Tracking Online Manual​​​​​​​

  • Order Tracking Webinar

  • Rotating Machinery Analysis Webinar

Main features

Order tracking module features:

  • Simple and easy to setup

  • Dedicated re-sampling method for sharp order separation

  • Measurement in the time domain to keep all benefits

  • 2D, 3D waterfall in order or frequency domain

  • Amplitude, phase extraction

  • Recalculation in post-processing

  • Phase synchronous rpm input with 12.5 ns resolution

For more information please visit the Order Tracking PRO training online course.

Cepstrum Analysis Determine Vibration Signatures

The cepstrum analysis calculation can be used to determine characteristics in speech analysis, and to enhance the analysis of vibration signatures such as gearbox and bearing frequencies. Dewesoft provides mirror spectrum, low and high-frequency outputs.

Dewesoft Cepstrum math offers settings for:

  • Selectable block size

  • Windowing

  • Liftering

  • Overlap and averaging

The video on the right side shows Cepstrum math being used on a microphone input signal to determine the speaker's name.