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NPSH Available & Margin

Net Positive Suction Head your installation actually delivers — versus what the pump demands — plus the suction specific speed.

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m
Open tank at sea level ≈ 10.13 m of water.
°C
Sets the vapour pressure of water.
m
Surface level to pump centreline. Negative for a suction lift.
m
Pipe, valves and fittings combined.
rpm
m³/h
m
From the pump datasheet.

Result

Fill in the fields — the result appears as you type.

Method & assumptions
NPSHa = Pabs + Hs − Pvap(T) − Hf · Nss = N·√Q(m³/s) ÷ NPSHr0.75

Vapour pressure of water interpolated from the standard 0–100 °C table. Margin = NPSHa − NPSHr; a positive margin above ~0.5 m is the usual comfort band. Nss uses the SI convention (m³/s).

Engineering aid only — verify results against the applicable code edition and the equipment datasheet before committing to a design.

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