HD Enveloping


HD ENV® enables the detection of gear and bearing faults very early on in the damage process, making it possible to closely monitor the development throughout the stages.

HD Enveloping takes vibration enveloping to a whole new level and is an ideal complement to conventional vibration techniques. Capable of detecting, at a very early stage, such machine problems which are generally difficult to find in good time with conventional techniques - for example gear damage and bearing damages - the method utilises cleverly engineered algorithms for digital signal processing to obtain optimal data for trending purposes.

Signals buried in machine noise are revealed through high definition digital enveloping, extracting and enhancing the signals of interest from the overall machinery vibration signal while preserving the true highest peaks. HD Enveloping can be used to monitor applications in the 15 - 20,000 RPM range.

Input data

To perform general machine condition trending, a signal from a vibration transducer and an rpm measurement is needed. For analysis and symptom trending, gear and bearing data are also required.

Filters and other options

A number of predefined filters are available to detect damages or anomalies in different stages of development; two of which are specifically designed for bearing monitoring and the others for special applications, both bearing and non-bearing applications.

Random Impact Rejection: Randomly occurring high readings which may cause false alarms are filtered out by means of the random impact rejection algorithm.
RPM fluctuations are handled with HD Order Tracking, see below.

The Symptom enhancement algorithm looks for repetitive impacts in the time domain. As a result, random signals are suppressed and repetitive signals enhanced. The output is an HD Env Time signal, where relevant bearing and gear data can be displayed.

Output data

  • •      HD Real Peak
  • The unit of measurement is HD Real Peak, a scalar value expressed in decibels. Representing the true highest peak found in the enveloped signal, HD Real Peak is the primary value to use for determining the severity of a bearing or gear damage. It is also used for triggering alarms.
  • •      HD Env Time Signal
  • HD Env Time Signal is useful to analyse the vibration measurements; for example locating a possible gear or bearing damage. In some cases, it is also possible to determine the nature of the damage (a single crack or spalling all around etc.).
  • •      HD Env Spectrum
  • HD Env Spectrum is the result of applying FFT algorithms on the HD Env Time Signal. The HD Env spectrum is useful to determine (1) where in the bearing a possible damage is located, and (2) the severity of the damage. It is also useful for trending purposes (applying symptom and band values).


HD Order Tracking

On machinery operating under variable speed, analysis with High Definition Order Tracking provides reliable data and crystal clear measuring results even when RPM varies greatly during the course of measurement. Order Tracking is applicable in a very wide RPM range, from just a few to thousands of revolutions per minute.

HD Order Tracking is approximately ten times better than traditional order tracking algorithms when RPM is not perfectly stable.