envelopeanalüüsi

Envelope analysis is a technique used in predictive maintenance to detect bearing and gear defects. It involves analyzing the high-frequency vibrations that are generated when a bearing or gear is damaged. These vibrations are often masked by lower-frequency vibrations from the machine itself, making them difficult to detect with conventional vibration analysis. Envelope analysis extracts these high-frequency signals by demodulating the vibration signal. This process effectively filters out the lower-frequency noise, leaving behind the characteristic impulses associated with impacts on the bearing or gear.

The process typically begins with the acquisition of vibration data from the machine using accelerometers. This raw data is then passed through a series of digital filters to isolate the frequency bands of interest where the defect signatures are expected to appear. A common approach is to use a band-pass filter followed by a squaring operation and then a low-pass filter. The squaring operation emphasizes the high-amplitude impulses, and the subsequent low-pass filter extracts the envelope of these impulses. The resulting signal, the envelope, can then be analyzed for the presence of specific frequencies that correspond to the rotational speeds of the bearing or gear components (e.g., inner race, outer race, ball, cage for bearings, or mesh frequencies for gears).

The effectiveness of envelope analysis lies in its ability to reveal subtle damage that might otherwise go unnoticed. By focusing on the high-frequency energy released during impact events, it can provide early warning of impending failure, allowing for planned maintenance and preventing costly breakdowns. This makes it a valuable tool for condition monitoring of rotating machinery in various industries.