Absolute pressure at pump suction above vapor pressure in meters. NPSHa must exceed NPSHr.

What causes cavitation?

When NPSHa<NPSHr, liquid vaporizes. Vapor bubbles collapse causing damage.

How much margin needed?

Minimum: NPSHa≥NPSHr+0.5m. Recommended: NPSHa≥1.3×NPSHr.

Higher temp=higher vapor pressure=less NPSHa. Water at 80°C: Pv=47.4kPa.

Raise tank, reduce friction, pressurize tank, cool fluid.

Free Engineering Tool — #156

Calculate NPSHa from suction conditions. Prevent cavitation.

NPSHaCavitation Check

NPSHa (Available)

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P_atm as Head

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Gauge as Head

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Vapor as Head

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