Which term defines the pressure head available at the pump suction to prevent cavitation?

• A. Flow head
• B. TDH
• C. NPSH available
• D. NPSH required

Answer: (C)

Cavitation risk in a pump is managed by keeping enough energy head at the suction to prevent the liquid from flashing into vapor. The term that describes the pressure head that is actually available at the pump suction to resist that vaporization is NPSH available. It represents the suction-side energy (in head units) that remains to keep the liquid from cavitating, considering static suction head, velocity head, and suction losses, relative to the liquid’s vapor pressure. If NPSH available is sufficient—specifically, if NPSHa is greater than the pump’s required NPSH (NPSHr)—cavitation is avoided.

The other terms don’t describe suction-head availability in the context of cavitation. TDH is the total head the pump must overcome in the system, not the head available at suction. NPSH required is the amount of head the pump itself needs to avoid cavitation, a property of the pump and operating point, not what’s available at suction. Flow head isn’t a standard measure used to describe suction head for cavitation control.