Horsepower Formula for Pumps

Pump Brake Horsepower Formula:

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

Flow Rate (GPM):

gpm

Head:

Specific Gravity (SG):

unitless

Efficiency (Eff):

decimal

Pump Brake Horsepower (HP):

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1. What is the Horsepower Formula for Pumps?

The Horsepower Formula for Pumps calculates 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:

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

Where:

\( HP \) — Pump brake horsepower (hp)
\( GPM \) — Flow rate in gallons per minute (gpm)
\( Head \) — Total dynamic head in feet (ft)
\( SG \) — Specific gravity of the fluid (unitless)
\( Eff \) — 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 fluid properties and pump efficiency.

3. Importance of Pump Horsepower Calculation

Details: Accurate horsepower calculation ensures proper motor selection, prevents underloading or overloading, optimizes energy consumption, and extends equipment life in pumping systems.

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 (e.g., 0.75 for 75% efficiency). 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: Why is specific gravity important in the calculation?
A: Specific gravity accounts for fluid density differences. Heavier fluids require more power to pump than lighter fluids at the same flow rate and head.

Q3: What is a typical pump efficiency range?
A: Pump efficiencies typically range from 50% to 85%, depending on pump type, size, and operating conditions.

Q4: How does head affect horsepower requirements?
A: Higher head requires more horsepower. Horsepower is directly proportional to head for a given flow rate and specific gravity.

Q5: Should I add a safety factor to the calculated horsepower?
A: Yes, it's common practice to add a 10-20% safety factor to account for system variations, wear, and future requirements.