Pump Selection & System Curve Calculator — NPSH

CAPCO

FEL-3 Pump Selection & System Curve Engine — Centrifugal Pumps

PUMP CURVE SYSTEM CURVE NPSH ANALYSIS

Fluid Properties

Fluid description

Density (ρ)

kg/m³

Viscosity (μ)

Vapour pressure (Pv)

kPa abs

Liquid temperature

°C

System Curve Inputs

Static head (elevation + pressure diff.)

Suction-side pipe ID

Discharge-side pipe ID

Suction pipe length

Discharge pipe length

Pipe roughness (ε)

Total K — fittings (suction)

—

Total K — fittings (discharge)

—

Design flow rate

m³/h

Pump Curve — Polynomial Coefficients

H = A − B·Q − C·Q² | Enter from pump datasheet or catalogue. Default = typical end-suction centrifugal.

A — shutoff head

B — linear coeff.

m·h/m³

C — quadratic coeff.

m·h²/m⁶

Pump efficiency at BEP (%)

BEP flow rate

m³/h

Rated speed (N)

rpm

Motor efficiency

NPSHr at BEP

NPSHr margin factor

m (add)

NPSH Available — Suction System

Suction vessel pressure (Ps)

kPa abs

Suction static head (Zs)

m (+ above pump)

NPSHa = (Ps − Pv)/(ρg) + Zs − hf_suction

Affinity Laws — Speed Variation

Speed 1

rpm

Speed 2

rpm

Speed 3 (rated)

rpm

H-Q Pump & System Curves

Pump curve (rated) System curve Speed variants NPSHa / NPSHr

Efficiency & Shaft Power vs. Flow

Efficiency (%) Shaft power (kW)