Defining acoustic emission-based condition monitoring indicators for monitoring piston rod seal and bearing wear in hydraulic cylinders

Abstract

Fluid leakage from hydraulic cylinders is a major concern for the offshore industries as it directly affects hydraulic cylinder energy efficiency and causes environmental contamination. There have been attempts made in literature to develop robust condition monitoring techniques for hydraulic cylinders. However, most of these studies were performed to identify degradation of single components. Therefore, in this study, the aim is to monitor degradation of multiple components simultaneously in hydraulic cylinders using acoustic emissions. Experiments performed consist of three test phases and were performed using a hydraulic test rig. In the first test phase, the study is performed to identify acoustic emission features that can be used to monitor piston rod seal wear. In the second test phase, acoustic emission features are identified that can be used to understand bearing wear when unworn, semi-worn or worn piston rod seals are used in hydraulic test rig. In the third test phase, a run-to-failure test is conducted to identify acoustic emission features that can indicate fluid leakage initiation due to piston rod seal wear. The median frequency feature showed good repeatability in all the three test phases to identify piston rod seal wear, bearing wear and fluid leakage initiation during the initial stages in the hydraulic test rig. The proposed acoustic emission-based condition monitoring technique is robust and can be used for the hydraulic cylinders in the industries, as it identifies acoustic emission features based on particular frequency bands associated to specific components, making it less susceptible to noise from other components.

Acoustic Emission-Based Condition Monitoring and Remaining Useful Life Prediction of Hydraulic Cylinder Rod Seals

“…From the frequency domain analysis, the frequency band between 60 and 80 kHz was identified as the frequency band in which the seal wear is most prominent for the experiments conducted in this study. Thus, the identified frequency bands for seal wear of both the experiments of Shanbhag et al [23] and the current experiments in this paper occur in an overlapping frequency region. In Figure 13, the bandpass filtered RMS series from all tests show that the initial decreasing trend is removed from the RMS series.…”

“…In Figure 13, the bandpass filtered RMS series from all tests show that the initial decreasing trend is removed from the RMS series. This implies that the run-in period could not be identified in the experiments of Shanbhag et al [23] due to the bandpass filter. However, because the frequency band in the experiments of Shanbhag et al [23] increased to 100 kHz, whereas in the current research it was only shown up to 80 kHz, it cannot be excluded that the run-in period may be identified if the same bandpass filter were applied.…”

“…A similar theory is examined in other research that investigates the relationship between friction and wear [14,21,22]. Shanbhag et al [23] performed a similar RTF test with a similar experimental setup. This RTF test was run continuously for approximately 17 h using all unworn seals.…”

“…Shanbhag et al [23] performed a similar RTF test with a similar experimental setup. This RTF test was run continuously for approximately 17 h using all unworn seals.…”

“…However, in their experiment, the authors did not experience a similar initial large decrease in RMS energy. Shanbhag et al [23] utilized a bandpass filter from 50 to 100 kHz in their experimental tests, because the authors previously identified this frequency band to correspond to the seal wear process. It should be noted that, in this previous study, the type of AE sensor, and its placement directly on the rod, was the same as that used in the RTF tests 1 and 3 in the present research.…”