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NPSHa
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Status
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Equivalent pressure
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Recommended: rectangle / responsive unit
Recommended: rectangle / responsive unit
Formula
NPSHa = ((Pabs - Pvapor) × 10.197 / SG) + z - hf
Variable description:
- NPSHa = Net Positive Suction Head Available, unit: m
- Pabs = Absolute pressure at liquid surface or suction vessel, unit: bar(a)
- Pvapor = Vapor pressure of liquid at pumping temperature, unit: bar(a)
- SG = Specific gravity of liquid, dimensionless
- z = Static head, unit: m
- hf = Friction loss in suction line, unit: m
Sign convention for z:
- Use positive value when liquid level is above pump centerline
- Use negative value when pump centerline is above liquid level
Engineering note: This equation is valid when Pabs is the pressure at the liquid surface or inside the suction vessel, not the pump suction nozzle pressure.