ThermoFluidCalc Engineering Report

Centrifugal Pump NPSHa & Cavitation Safety Analysis — 2026-08-23 20:57:04
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🌀 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.

⚡ Fortran 90 Engine Double Precision (IEEE 754) ✓ ISO / ASME Validated
📊 Solver Telemetry ● ACTIVE
👁️ Consultations 35
⚡ Calculs faits 28
💾 Téléchargements 133 📦 Code Fortran 4.5 KB
📅 Mise en service Jun 2026
⏱️ Latence < 1 ms
⚡ Outils & Rapports :
💾 Télécharger Fortran 90

🌀 Centrifugal Pump Suction Hydraulics & Impeller Eye Cavitation Zone

Real-time visual simulation: Suction tank liquid level, line losses, and vapor bubble collapse in impeller eye

📝 Configuration & Presets

💧 Flooded Suction Water (Safe) ⚠️ River Suction Lift (-4m) 🔥 Boiler Feed Deaerator (130°C) ⛽ Volatile Gasoline Solvent
🧪 Fluid Selection & Vessel State
📏 Suction Piping & Static Level
+ Flooded, - Suction Lift
Elbows, valves, strainer, inlet
⚙️ Pump Required Performance
From pump manufacturer curve (3% head drop)
Hydraulic Institute (HI 9.6.1) NPSH Formulation:
• NPSH Available: NPSHa = (Pvessel − Pv(T)) / (ρ g) + zs − hloss [m]
• Cavitation Margin: ΔNPSH = NPSHa − NPSHr ≥ 0.6 m (or CMR ≥ 1.2 - 1.5)
• Thoma Cavitation Number: σ = NPSHa / Hpump
• Velocity Limit: Suction velocity V should remain between 1.0 - 2.5 m/s.

📊 NPSH & Cavitation Results

📊 Output Summary
💾 Fortran Source

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: ≥ +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 °C
Suction Piping Head Loss 4.13 m Friction + Minor losses

📈 NPSHa & NPSHr (m) vs Flow Rate Q (m³/h)

📉 NPSHa (m) vs Fluid Temperature T (°C)

=================================================================
 THERMOFLUIDCALC — 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)
=================================================================

📘 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.