Sammendrag
External leakage from hydraulic cylinders is of a major
concern for the offshore oil and gas industry. This occurs
mainly as a result of physical damage to the piston rod or due
to degradation of the piston rod seals. Numerous studies have
been conducted to diagnose leakage from hydraulic cylinders
due to seal failure using fluid, pressure, accelerometer or
acoustic emission-based condition monitoring techniques.
However, very few attempts have been made to diagnose
multiple faults in hydraulic cylinders at the same time.
Therefore, in this study, acoustic emission-based condition
monitoring technique is used to detect and separate acoustic
emission features due to different faults that are observed in
hydraulic cylinders. An experimental study was performed
on a test rig using water glycol as hydraulic fluid.
Experiments were performed with different combinations of
seals (unworn, semi worn and worn seals), and piston rods
(unworn and worn). Acoustic emission features such as root
mean square, peak, mean, kurtosis, skewness, mean
frequency, median frequency and bandpower were used to
identify seal and rod conditions. By using acoustic emission
median frequency and mean frequency features it was
possible to detect and separate leakage, and seal and rod
degradation in the test rig over a large range of hydraulic
working pressures. This study indicates that acoustic
emission monitoring can be a strong basis for future research
to identify and segregate other types of faults that are
observed in hydraulic cylinders.
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