NPSH (Net Positive Suction Head)
Definition
The absolute pressure at the pump inlet above vapor pressure, expressed as head. NPSHa (available) must exceed NPSHr (required by pump) to prevent cavitation. NPSHa = Ha - Hvp - Hf - Hs.
Practical Note
Maintain NPSHa > NPSHr + 0.5-1.0m margin. Improve NPSH by: raising liquid level, reducing suction pipe friction, lowering liquid temperature, or increasing suction tank pressure.