Connecting Rod Bearing Impact Vibrations in High Speed Industrial Gas Engines Using Acceleration vs. Crank-Angle, Non-Phased Vibration Time Waveforms & FFT Spectral Analysis
Connecting rod bearing impact analysis can identify the early stages of crankshaft bearing failure before substantial damage occurs. Unfortunately, almost all beginning and most experienced equipment analysts are unwilling to make bearing condition calls. Portable reciprocating engine analyzers can provide vibration vs. crank-angle displays that show impacting of the bearing shell and crank throw in relation to normal engine events including top dead center (TDC) and bottom dead center (BDC) piston reversals. The use of non-phased high-density acceleration time waveforms and FFT plots will be explained to add confidence in the bearing failure diagnosis. Trending of overall acceleration levels will be examined to aid in determining the rate of change in the developing bearing failure. Typical engine types covered by this procedure include 300 to 8000 horsepower, high speed, spark-ignited gas engines. A brief discussion of the required instrumentation, setup and data acquisition process is included in the body of the paper. A complete description of the procedure used is presented with examples of real data and photos that show a damaged bearing identified by this method.