FT-07 · Equipos rotativos

Centrifugal pump selection

Scales the rated point and the characteristic curve for speed and impeller trim, estimates Ns and finds the intersection with a system curve.

Rated point and adjusted condition

Rated flow rate Q₁ · Carga nominal H₁ · Shaft power P₁ · Speed N₁ · rpmImpulsor D₁ · Shut-off ratio H₀/HnomNew speed N₂ · rpmNew impeller D₂ · System static head · System head at Q₂ · Sets the constant of the system curve

Adjusted flow rate Q₂

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Carga ajustada H₂

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Adjusted power P₂

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Specific speed Ns

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Hydraulic family

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Estimated operating point

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Pump and system curves

Combined affinity laws

\[\frac{Q_2}{Q_1}=\frac{N_2}{N_1}\frac{D_2}{D_1}\]

\[\frac{H_2}{H_1}=\left(\frac{N_2}{N_1}\frac{D_2}{D_1}\right)^2\qquad \frac{P_2}{P_1}=\left(\frac{N_2}{N_1}\frac{D_2}{D_1}\right)^3\]

\[N_s=\frac{N\sqrt{Q}}{H^{3/4}}\]

Pump affinity laws calculator

The affinity laws transfer an operating point when the rotational speed changes or, approximately, when the impeller diameter changes. Flow, head and power scale with exponents 1, 2 and 3.

Interpreting specific speed

Approximate metric Ns	Familia	Dominant geometry
<10	Slow radial	High head, low flow
10–35	Radial	Conventional centrifugal impeller
35–80	Mixto	Radial and axial components
>80	Axial	High flow, low head

System curve and operating point

The actual flow rate sits at the intersection of the pump H-Q curve and the head the system requires. Changing the speed shifts the curve and changes the power demand.

Preguntas frecuentes

Can I trim the impeller a lot?

Extrapolating large trims with the simple laws is not recommended; consult the manufacturer's curves.

Does efficiency stay constant?

The ideal law assumes so near the equivalent point, but real efficiency does change.

What else should I check before selecting?

Available NPSH, margin, preferred operating range, motor power, materials and transient conditions.