What is NPSH and how do you prevent cavitation in pumps?

NPSH (Net Positive Suction Head) is the absolute pressure available at pump suction minus vapor pressure of the liquid. NPSH_available = (P_atm - P_vapor)/ρg + h_s - h_f, where h_s is suction head and h_f is friction loss. NPSH_required is specified by pump manufacturer. Cavitation occurs when NPSH_A < NPSH_R, causing vapor bubble formation and collapse, damaging impeller. Prevention methods: increase suction tank level, reduce suction pipe losses, use larger suction pipes, reduce liquid temperature, select pump with lower NPSH_R, or use a booster pump.