Pump Horsepower (HP) 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)

Pump 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 for pump selection and system design.

2. How Does the Calculator Work?

The calculator uses the standard pump horsepower formula:

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

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total dynamic head in feet (ft)
\( SG \) — Specific gravity of the fluid (1.0 for water)
\( \eta \) — Pump efficiency as a decimal (0.0-1.0)
3960 — Conversion factor (GPM·ft·lb/min per HP)

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

3. Importance of Pump HP Calculation

Details: Proper horsepower calculation ensures correct pump sizing, prevents motor overload, optimizes energy usage, and maintains system efficiency.

4. Using the Calculator

Tips:

For water systems, use SG = 1.0
Typical pump efficiencies range from 0.5 to 0.9 (50-90%)
Always add a safety factor (10-20%) to calculated HP
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 inefficiencies (what the motor must actually deliver).

Q2: How do I account for motor efficiency?
A: Divide the calculated HP by the motor efficiency to get required input power (wire-to-water efficiency).

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

Q4: How does viscosity affect HP requirements?
A: Higher viscosity increases power requirements and may reduce pump efficiency - specialized calculations are needed.

Q5: Should I round up the calculated HP?
A: Yes, always select the next standard motor size above your calculated requirement.