Pump Horsepower Calculator

Pump Horsepower Formula:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Flow Rate (Q):

GPM

Head Pressure (H):

feet

Specific Gravity (SG):

(dimensionless)

Pump Efficiency (η):

(0-1 decimal)

Pump Horsepower (HP):

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1. What is Pump Horsepower?

Pump horsepower (HP) is the power required to move a fluid at a specified flow rate against a given head pressure, accounting for the fluid's specific gravity and the pump's efficiency. It's a crucial parameter in pump selection and system design.

2. How Does the Calculator Work?

The calculator uses the standard pump horsepower equation:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total head in feet
\( SG \) — Specific gravity of the fluid (dimensionless)
\( \eta \) — Pump efficiency (decimal between 0 and 1)
3960 — Conversion factor (foot-pounds per minute per horsepower)

Explanation: The equation calculates the theoretical power required to move the fluid, then divides by pump efficiency to get actual required horsepower.

3. Importance of Pump HP Calculation

Details: Accurate horsepower calculation ensures proper pump selection, prevents motor overload, and helps design efficient fluid systems. Undersizing can lead to pump failure, while oversizing wastes energy.

4. Using the Calculator

Tips:

For water at standard conditions, use SG = 1.0
Typical pump efficiencies range from 0.5 to 0.9 (50-90%)
Include all system losses in total head calculation
For viscous fluids, additional corrections may be needed

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between hydraulic HP and brake HP?
A: Hydraulic HP is the theoretical power needed to move the fluid, while brake HP includes pump efficiency and is the actual power required at the pump shaft.

Q2: How does viscosity affect horsepower?
A: Higher viscosity increases power requirements and may reduce pump efficiency. Special calculations are needed for highly viscous fluids.

Q3: What's a typical pump efficiency value?
A: Centrifugal pumps typically range from 50-85% efficiency, while positive displacement pumps can reach 90% or more.

Q4: Why is the 3960 factor used?
A: It converts (GPM × feet × lb/gal) to horsepower (1 HP = 33,000 ft-lb/min, and water weighs 8.34 lb/gal: 33,000/8.34 ≈ 3960).

Q5: Should I add a safety factor?
A: It's common practice to add 10-20% safety margin to the calculated HP to account for system variations and future needs.