Abstract: The sudden fault on the low speed and heavy duty equipments are very difficult to recognize and it can bring about great loss. Though the equipments can be maintained by the vibration monitoring technology, the fault information on the low speed shaft can’t be easily picked through the frequency spectrum analysis. The necessary information on the low frequency range can be obtained by wavelet analysis on the monitoring data. The sultation coefficient of wavelet decomposition on the vibration signal in some time range can be regarded as the characteristic value to judge the fault. Furthermore, the cofficients can capture the developing process of the fault. For the same series monitoring data, the refinable spectrum analysis and FFT analysis compounding wavelet decomposition are both used to complete the comparative research. The achievements show that the refinable spectrum method can’t predict the fault reason and location. On the other hand, after the composite signal processing through wavelet analysis and FFT technique, the vibration amplitudes variation of the characteristic fre-quency of the hidden fault are very intense. As a result, it is very helpful to precisely recognize the early fault on the low speed and heavy duty equipments.

Key words: Low-speed heavy-duty, Spectrum analysis, Wavelet analysis