Pump Horsepower Calculator

Pump Horsepower Formula:

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

Flow Rate (Q):

GPM

Head (H):

Specific Gravity (SG):

(1 for water)

Efficiency (η):

decimal (0-1)

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, 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 pump horsepower equation:

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

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total dynamic head in feet (ft)
\( SG \) — Specific gravity of the fluid (dimensionless)
\( \eta \) — Pump efficiency as a decimal (0-1)
3960 — Conversion factor (ft·lb/min per HP)

Explanation: The equation calculates the power needed to move a fluid considering the work done against gravity (head) and the fluid's density (specific gravity), adjusted for the pump's efficiency.

3. Importance of Pump HP Calculation

Details: Accurate horsepower calculation ensures proper pump selection, prevents motor overload, optimizes energy consumption, and helps design efficient fluid systems.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1 for water), and pump efficiency (typically 0.7-0.9 for centrifugal pumps). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between brake HP and water HP?
A: Water HP is the theoretical power needed to move the fluid, while brake HP includes the pump's inefficiencies (what the motor must actually deliver).

Q2: How do I estimate pump efficiency?
A: Centrifugal pumps typically range from 50-85% efficiency. Check manufacturer curves for specific pumps at your operating point.

Q3: What if my fluid isn't water?
A: Use the specific gravity of your fluid (ratio of its density to water's density at 60°F).

Q4: How does viscosity affect pump HP?
A: Higher viscosity fluids generally require more HP due to increased friction losses (not accounted for in this basic formula).

Q5: Should I add a safety factor?
A: Engineers often add 10-20% to calculated HP to account for system uncertainties and future scaling.