A centrifugal pump exhibits high vibration. What are the possible causes and diagnostic approach?

Causes include: mechanical (imbalance, misalignment, bearing wear, loose components), hydraulic (cavitation, recirculation, operation away from BEP, air entrainment), and resonance (structural or acoustic). Diagnostic approach: vibration spectrum analysis - 1x rpm indicates imbalance/misalignment, 2x rpm indicates misalignment/looseness, vane pass frequency indicates hydraulic issues. Check operating point relative to BEP, verify NPSH margin, inspect bearings, check alignment, and verify foundation condition. Flow-induced vibration varies with flow rate; mechanical issues are relatively constant.