NPSH Calculator
Estimate NPSHa from suction-side conditions so you can screen for cavitation risk before pump selection is frozen.
Vapor pressure
0.042 bar
Suction pressure head
18.35 m
Vapor pressure head
0.43 m
Estimated NPSHa
16.42 m
Formula reference
NPSHa formula
NPSHa = Suction Pressure Head - Vapor Pressure Head - Line Loss
Pressure to head
Head (m) = Pressure (bar) x 10.197 / Specific Gravity
Vapor pressure is estimated with a water-based Antoine correlation. For hydrocarbons, solvents, or mixed chemicals, verify NPSHa with process-specific data.
Need help validating suction conditions?
Review our pump catalogue for centrifugal, submersible, chemical, and vacuum models used in demanding suction-side services.
View PumpsWhy NPSHa matters
NPSHa is the suction-side energy margin available to the liquid before vaporization begins. If the available NPSH falls too close to the pump's required NPSHr, cavitation can appear as noise, vibration, capacity loss, and premature seal or impeller damage.
What this estimate assumes
This calculator converts suction pressure to head, subtracts a water-based vapor pressure estimate, and then subtracts suction line loss. It is useful for screening atmospheric tanks, pressurized vessels, and simple suction headers before you move to detailed vendor-curve review.
Where extra review is required
Review the result carefully when the fluid is not water, when the line contains flashing liquids or dissolved gas, or when suction conditions change with tank level and process temperature. In those cases, process-specific vapor pressure data and a more complete suction model should replace this quick estimate.
よくある質問
What is a safe NPSH margin?
Many projects look for a margin above NPSHr rather than matching it directly. The right margin depends on service criticality and the vendor's guidance.
Why does temperature reduce NPSHa?
Higher liquid temperature raises vapor pressure. As vapor pressure rises, less suction-side energy remains available before flashing begins.
Does this result include tank level effects?
Only if the suction pressure input already reflects the actual condition at the source. For changing tank levels or vacuum service, update the suction pressure accordingly.
免責事項: This calculator uses a water-based vapor pressure estimate and should be verified for process-critical services.