Submersible Pump Horsepower Calculator

Pump Horsepower Formula:

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

Flow Rate (Q):

GPM

Head (H):

feet

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 for selecting and sizing pumps.

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
\( SG \) — Specific gravity of the fluid (1.0 for water)
\( \eta \) — Pump efficiency as a decimal (0.0 to 1.0)
3960 — Conversion factor to horsepower

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

3. Importance of Horsepower Calculation

Details: Proper horsepower calculation ensures you select a pump with adequate power for your application while avoiding oversized, inefficient pumps. It's essential for energy efficiency and system longevity.

4. Using the Calculator

Tips:

For water applications, use SG = 1.0
Typical pump efficiency ranges from 0.5 to 0.9 (50-90%)
Total head includes static head, friction losses, and pressure differences
Always round up to the nearest standard motor size

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. Brake HP is the actual power required by the pump (including inefficiencies).

Q2: How do I determine pump efficiency?
A: Efficiency is typically provided by the manufacturer. For estimation, centrifugal pumps are often 50-85% efficient, while positive displacement pumps can be 80-90% efficient.

Q3: Why is specific gravity important?
A: Heavier fluids (SG > 1) require more power to pump than water. Lighter fluids (SG < 1) require less power.

Q4: What safety factor should I add?
A: Common practice is to add 10-20% to the calculated HP to account for system variations and future needs.

Q5: How does viscosity affect horsepower?
A: High viscosity fluids increase friction losses and may require special pump designs. The standard formula works best for water-like viscosities.