A study of hydraulic seal integrity

The work described in this paper involved on-line detection of seal defects in a water hydraulic cylinder. An obvious effect of seal defect is internal leakage. Therefore, the approach used was to detect the internal leakage using suitable technique. The technique used involved detecting the acoustic emission (AE) due to the internal leakage. This paper evaluated various parameters of AE signals in terms of their capability in estimating the internal leakage rate in a water hydraulic cylinder. Experiments were carried out to study the characteristics of AE parameters at different internal leakage rates, the parameters including the root-mean-square (rms) value, the count rate, the peak magnitude of power spectral density and the energy. The correlations between these parameters and the internal leakage rate were analysed carefully. The results show that energy-based AE parameters, especially the rms value, are more suitable to interpret AE signals generated by internal leakage.