Pumps and Compressors Troubleshooting — real-world interview & field troubleshooting questions with clear, practical answers. Tap any question to open its answer. Showing the first 70 questions free. The complete question bank is available as a PDF below. CENTRIFUGAL PUMP CAVITATION & NPSH PROBLEMS Q1 A centrifugal pump makes a loud gravel-cracking noise, vibrates, and head collapses. What is occurring? Answer Classical cavitation. Net Positive Suction Head Available (NPSHA) fell below NPSH Required (NPSHR). Fluid pressure dropped below vapor pressure at the impeller eye, forming vapor bubbles that collapse violently against the metal, eroding the impeller. Q2 How do you distinguish between classic suction cavitation and discharge recirculation cavitation? Answer Suction cavitation occurs under high flow and low suction head, pitting the visible front suction side of impeller vanes. Discharge recirculation occurs under low flow (throttled discharge), eroding the pres...