A Proven Approach to Condition Monitoring for Reciprocating Machinery

  • By Ken Keith
  • one year ago
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Traditional Vibration Analysis (VA) or Spectrum VA is widely utilized on rotating machinery in all types of industrial applications to diagnose and troubleshoot machinery issues. In conjunction with other technologies, VA allows predictive maintenance personnel to pinpoint machinery failures like unbalance, misalignment, bearing issues, etc. This diagnosis is completed by analyzing the vibration frequency spectrum of an event and its correlation to the machine and conditions. For reciprocating machinery, however, spectrum analysis is not the most effective tool for determining defects as the expected mechanical events and the failure modes are best identified in a time-based waveform and referenced to a known point on each cylinder such as Top Dead Center (TDC). In the reciprocating analysis world, this is known as crank angle-based data, which does not utilize the frequency spectrum, but rather examines events relative to crankshaft positions. By combining vibration in different frequency ranges with in-cylinder pressure data and utilizing basic thermodynamic and combustion principles, it is possible to determine defects in reciprocating machine equipment such as compressor cross head damage and cylinder leakage (valves, rings, and packing) as well as engine valve train and cylinder-related issues. This paper will provide an overview of engine and compressor analysis and explain how crank angle-based data can pinpoint issues as compared to traditional VA. A review of ISO Guidelines for reciprocating compressors will also be discussed.