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Gearbox Fault Diagnosis Methods

Release date:

2022-05-23

A gearbox is a unified mechanical assembly that houses both gears and bearings. Any gearbox failure—whether caused by manufacturing defects or operational stress—deserves careful attention. Generally, the following methods are commonly used to diagnose gearbox issues.

Gearbox It is a unified mechanical body where gears and bearings coexist. Various faults caused by processing defects or pressure deserve attention. Gearbox Generally speaking, the following methods are usually used to diagnose gearbox faults.

1. Cepstrum Analysis Method

Cepstrum analysis, also known as secondary spectrum analysis, is a new technology in modern signal processing science. When multiple modulation sidebands that are difficult to identify appear in the mechanical signal spectrum, cepstrum can decompose and identify fault frequencies and analyze the causes of faults.

For the vibration spectrum of several pairs of meshing gears, Gearbox since each pair of gears produces sidebands during meshing, when these sidebands intertwine and concentrate, merely refining frequency identification and analysis is far from enough. This is because cepstrum transforms harmonics in the power spectrum into single spectral lines in the cepstrum, whose positions also imply the frequency ranges of the corresponding harmonics in the power spectrum.

Another significant advantage of cepstrum is its insensitivity to the signal transmission path of sensors or the orientation reflection of measurement points, as well as its insensitivity to the correlation between frequency adjustment and amplitude. This, in turn, helps monitor the magnitude of fault signals without needing to measure the specific amplitude value at a certain point.

2. Sideband Analysis Method

Generally, sidebands are analyzed from two aspects: one is comparing the range of sideband amplitudes during each measurement; the other is using the symmetrical characteristics of sideband frequencies to check specific frequency relationships and determine whether they belong to the same group of sidebands. If so, the modulation signal frequency and Gearbox the meshing frequency can be obtained.

It should be noted that individual faults such as gear tooth loss, root cracks, or broken teeth will show obvious transient modulation, and a series of sidebands will appear in the meshing direction and on both sides, mainly manifested as dense orders and scattered spectral lines. Due to the overlap of high-order frequency converters, the shape of sidebands varies. If there are obvious local faults, they can also promote the increase of harmonic components and their rotational frequencies.

Here, the sideband components contain rich Gearbox fault information resources. To obtain this information, sufficient frequency resolution is required in spectral analysis to facilitate precise measurement of distances between sidebands.

3. Power Spectrum Analysis Method

The power spectrum is a concept of statistical averaging of random processes; the power spectrum of a stationary random process is a deterministic function. This method can determine Gearbox the frequency composition of vibration signals and the distribution of vibration energy across frequencies. Because the power spectrum relates to amplitude squared, compared to amplitude spectrum, the power spectrum can highlight linear spectral components of harmonics and meshing frequencies, reducing a series of "spikes" caused by vibration signals.

Besides the chemical industry, Gearbox it is also widely used in other fields. After a failure occurs, one should not rush to take many measures to correct it. Instead, the root cause of the fault should be analyzed first, identifying where it occurs, finding safety hazards, and choosing appropriate strategies and methods for handling and diagnosis. This approach can achieve twice the result with half the effort.

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