Surface pressure · suction head · losses · vapor head
NPSH-available head budget
Inputs
User-entered absolute pressure head at the liquid surface; atmospheric or tank pressure is not derived.
User-entered liquid-surface-to-pump elevation contribution; use positive for a stated flooded-suction contribution and negative for a stated lift.
User-entered total suction-side loss head; no pipe, valve, fitting, or flow model is solved.
User-entered vapor-pressure head at the stated fluid condition; fluid properties and temperature are not derived.
User-entered pump-data reference used only for a literal stated-head difference; it is not assessed for adequacy.
Results
Literal NPSH availableNPSHa
7.53
Declared NPSH-required reference
3
Literal NPSHa − declared NPSHr difference
4.53
Declared signed static suction head
-2
NPSHa = Hsurface + Hsuction − Hloss − Hvapor; stated difference = NPSHa − NPSHr
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Hydrostatic pressure · Flow continuity · Pipe mean velocity · Bernoulli equation
Method
Formula, when it applies, and when it does not
Sum suction-side head terms into a NPSH-available value and a NPSH-required reference difference without selecting a pump or deciding cavitation adequacy.
NPSHa = Hsurface + Hsuction − Hloss − Hvapor; stated difference = NPSHa − NPSHr
When
- Declared suction loss and vapor-pressure heads
Don’t
- This sums only user-declared surface-pressure, signed static-suction, suction-loss, and vapor-pressure heads, then subtracts a user-declared NPSH-required reference. It does not calculate properties, determine vapor pressure, derive losses, select a pump, determine cavitation risk, establish NPSH margin adequacy, capacity, safety, suitability, or approval.
Hydraulic Institute — NPSH definition