๐ Centrifugal Pump NPSH Available & Cavitation Sizer
Calculate centrifugal pump NPSH available (NPSHa), cavitation safety margin (NPSHa - NPSHr), vapor pressure, suction pipe friction losses, and Thoma cavitation parameter.
โก Fortran 90 Engine
Double Precision (IEEE 754)
โ ISO / ASME Validated
Fluid Mechanics
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Released
Jun 2026
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< 1 ms
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๐ Centrifugal Pump Suction Hydraulics & Impeller Eye Cavitation Zone
Real-time visual simulation: Suction tank liquid level, line losses, and vapor bubble collapse in impeller eye๐ Configuration & Presets
๐ง Flooded Suction Water (Safe)
โ ๏ธ River Suction Lift (-4m)
๐ฅ Boiler Feed Deaerator (130ยฐC)
โฝ Volatile Gasoline Solvent
Hydraulic Institute (HI 9.6.1) NPSH Formulation:
โข NPSH Available: NPSHa = (Pvessel โ Pv(T)) / (ฯ g) + zs โ hloss [m]
โข Cavitation Margin: ฮNPSH = NPSHa โ NPSHr โฅ 0.6 m (or CMR โฅ 1.2 - 1.5)
โข Thoma Cavitation Number: ฯ = NPSHa / Hpump
โข Velocity Limit: Suction velocity V should remain between 1.0 - 2.5 m/s.
โข NPSH Available: NPSHa = (Pvessel โ Pv(T)) / (ฯ g) + zs โ hloss [m]
โข Cavitation Margin: ฮNPSH = NPSHa โ NPSHr โฅ 0.6 m (or CMR โฅ 1.2 - 1.5)
โข Thoma Cavitation Number: ฯ = NPSHa / Hpump
โข Velocity Limit: Suction velocity V should remain between 1.0 - 2.5 m/s.
๐ NPSH & Cavitation Results
๐ Output Summary
Net Positive Suction Head Available (NPSHa)
1.83 meters
NPSHr: 2.50 m | Margin: -0.67 m (CMR = 0.73)
SEVERE CAVITATION (HEAD DROP & EROSION)
Cavitation Safety Margin
-0.67 m
HI Target: โฅ +0.60 m
Suction Line Flow Velocity
3.59 m/s
Recommended: 1.0 - 2.5 m/s
Fluid Vapor Pressure Pv
3.77 kPa
At 28 ยฐC
Suction Piping Head Loss
4.13 m
Friction + Minor losses
๐ NPSHa & NPSHr (m) vs Flow Rate Q (mยณ/h)
๐ NPSHa (m) vs Fluid Temperature T (ยฐC)
================================================================= THERMOFLUIDCALC โ PUMP NPSHa & CAVITATION ANALYSIS REPORT ================================================================= Case Title : River Intake Lift Pump (Negative Static Head) Fluid Medium : Water (Clean Potable / Industrial) Operating State : P_vessel = 1.013 bar abs, Temp = 28.0 C (Vapor Press Pv = 3.769 kPa) Suction Line Geometry : ID = 80.0 mm, Length = 12.0 m, sum K = 3.5, Static Head zs = -4.00 m Flow & Velocity : Q = 65.00 m3/h (18.06 L/s), Suction Velocity V = 3.59 m/s ----------------------------------------------------------------- NPSH AVAILABLE (NPSHa) : 1.831 meters (17.927 kPa) NPSH REQUIRED (NPSHr) : 2.500 meters (3% Head Drop Curve) CAVITATION SAFETY MARGIN : -0.669 meters (NPSHa - NPSHr) Cavitation Margin Ratio : 0.732 (NPSHa / NPSHr) Thoma Cavitation Number : 0.0610 (NPSHa / H_pump = 30.0 m) Total Suction Head Losses : 4.131 meters (Friction + Minor) CAVITATION RISK STATUS : SEVERE CAVITATION (HEAD DROP & EROSION) =================================================================
๐ Calculation Methodology & Hydraulic Institute Standards
Hydraulic Institute NPSH Margin (HI 9.6.1)
NPSH margin is the difference between $NPSH_a$ and $NPSH_r$. A margin of at least $0.6 - 1.5\,\text{m}$ (or $CMR \ge 1.3$) prevents vapor cavity collapse, impeller pitting erosion, and high-frequency vibration.
Vapor Pressure & Temperature Impact
As fluid temperature rises, vapor pressure $P_v(T)$ increases exponentially according to the Antoine equation, reducing $NPSH_a$ dramatically and demanding higher suction elevation or pressurization.
Key Engineering Assumptions
- Swamee-Jain / Darcy-Weisbach pipe friction model.
- Sum of minor losses $\sum K$ includes strainer, foot valve, elbows, and reducer.
- Applicable to water supply, chemical transfer, hydrocarbon pumps, and boiler feed deaerators.