Pump Horsepower Calculation Formula

Pump Horsepower Formula:

\[ HP = \frac{GPM \times Head \times SG}{3960 \times Efficiency} \]

Flow Rate (GPM):

gallons/min

Head:

Specific Gravity (SG):

unitless

Efficiency:

decimal

Brake Horsepower (HP):

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1. What is Pump Horsepower Calculation?

The Pump Horsepower Calculation determines the brake horsepower required to drive a pump based on flow rate, head, specific gravity, and pump efficiency. This is essential for proper pump selection and motor sizing in fluid systems.

2. How Does the Calculator Work?

The calculator uses the pump horsepower formula:

\[ HP = \frac{GPM \times Head \times SG}{3960 \times Efficiency} \]

Where:

\( HP \) — Brake horsepower required
\( GPM \) — Flow rate in gallons per minute
\( Head \) — Total dynamic head in feet
\( SG \) — Specific gravity of the fluid (unitless)
\( Efficiency \) — Pump efficiency as a decimal (0.0 to 1.0)
\( 3960 \) — Conversion constant

Explanation: The formula calculates the actual power required at the pump shaft, accounting for the energy needed to move the fluid and the pump's mechanical efficiency.

3. Importance of Pump Horsepower Calculation

Details: Accurate horsepower calculation is crucial for selecting properly sized pumps and motors, ensuring energy efficiency, preventing motor overload, and maintaining system reliability.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1.0 for water), and pump efficiency as a decimal (typically 0.5-0.9). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between brake horsepower and water horsepower?
A: Water horsepower is the theoretical power to move the fluid, while brake horsepower includes pump inefficiencies and is the actual power required at the pump shaft.

Q2: What is a typical pump efficiency range?
A: Pump efficiency typically ranges from 50% to 90%, depending on pump type, size, and operating conditions.

Q3: Why is specific gravity important?
A: Specific gravity affects the fluid density. Heavier fluids (SG > 1) require more power to pump, while lighter fluids (SG < 1) require less power.

Q4: How do I account for motor efficiency?
A: Motor efficiency is separate from pump efficiency. To find electrical power input, divide brake horsepower by motor efficiency.

Q5: What safety factors should be applied?
A: Typically add 10-25% safety factor to the calculated horsepower to account for system variations and ensure reliable operation.