Diagnosing shaft vibration signals has been a proven method for assessing sleeve bearings in rotating machinery for decades. A refinery operates a turbo compressor within the speed range of 7,000–8,700 rpm, exhibiting unusual vibration behavior. In the HD stage bearing, there were sudden changes in the peak-to-peak value between 8,130–8,185 rpm. KÖTTER Consulting Engineers conducted measurements and identified a vibration component at half the rotational frequency, indicating incorrect bearing clearance. After correction, the compressor operated flawlessly.