Envelope Analysis

Envelope Analysis is a well-known technique to extract periodic impacts from a machine’s vibration signal. The method is able to extract impacts with very low energy and even hidden by other vibration signals. This method is therefore a popular tool amongst maintenance personnel.

Bearing failures are one of the most common faults with industrial machines and the envelope analysis is primarily used to detect and diagnose REB (Rolling Element Bearing) faults. When a fault develops, the vibration becomes amplitude modulated due to periodic changes in the forces. The low frequency vibrations, including the REB fault symptoms, are filtered away in order only to extract the modulated periodic information from the more sensitive and pure envelope signal. The envelope spectrum has shown several major advantages over other methods in very early detection and fault symptom identification.

The popular amplitude demodulation method with the use of envelope spectra has many different names; ours are SED (Selective Envelope Detection) and BCS (Bearing Condition Signature).