Application of Wavelet Packet Transform and Envelope Analysis to Non-stationary Vibration Signals For Fault Diagnosis of a Reciprocating Compressor

摘要

Reciprocating compressors play a major role in manufacturing industries such as oil and gas refineries, petrochemical industrial plants, etc. Therefore, it is necessary to implement online condition monitoring for early and accurate detection of faults which if not fixed can lead to machine inefficiency, damage, or total system shutdown. This paper presents the application of wavelet packet transform (WPT) and envelope analysis to non-stationary vibration signal from a two-stage reciprocating compressor for fault diagnostics. Vibration signals measured on the reciprocating compressor consist of a series of impulsive events with non-stationary and random characteristics, which result mostly from mechanical impacts of the valves and impulsive fluid excitation of high-pressure turbulent flows. To characterise such vibration signals, WPT is employed to decompose them into the time-frequency domain for reliable extraction of diagnostic information. With the help of statistical based analysis, the most optimal terminal node of the wavelet packet is selected for envelope analysis. The first and the third harmonics of the envelope spectrum are found to be reliable for the classification of three common faults including intercooler leakage, second-stage discharge valve leakage and a combined fault under the wide range operating pressures of a reciprocating compressor.