Misalignment

A condition where two coupled rotating shafts are not collinear (their rotational centerlines do not coincide), causing increased vibration, accelerated wear of bearings, seals, and couplings, higher energy consumption, and premature failure. Misalignment is the #2 cause of premature machinery failure after contamination/poor lubrication. Types: (1) Angular — shaft centerlines intersect at an angle; causes axial vibration at 1× and 2× RPM. (2) Parallel (offset) — shaft centerlines are parallel but not coincident; causes radial vibration at 2× RPM (dominant). (3) Combined — the most common real-world condition. Vibration signature: dominant at 2× RPM in the radial direction (parallel), high axial vibration (angular), and harmonic pattern at 1×, 2×, 3× RPM. Tolerances per ISO 10816 and coupling manufacturer specs: typically <0.05 mm offset and <0.05 mm/100 mm angular for general industrial machinery. Detection: vibration analysis (screening), laser alignment tools (precise measurement). Even 0.1 mm of offset misalignment can reduce bearing life by 50%. Causes: thermal growth (hot running changes alignment from cold), soft foot (uneven machine feet), piping strain, and foundation settlement. Per API 686 (machinery installation) and ISO 10816.