Pump Horsepower Calculation

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)

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 in pump selection and system design.

2. How Does the Calculator Work?

The calculator uses the 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 (foot-pounds per minute per horsepower)

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 Horsepower Calculation

Details: Proper horsepower calculation ensures correct pump selection, prevents motor overload, and optimizes energy consumption. Undersized pumps won't meet system demands, while oversized pumps waste energy and may cause operational issues.

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%). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is specific gravity?
A: Specific gravity is the ratio of a fluid's density to water's density at 60°F. Water has SG=1.0, while heavier fluids have SG>1.0.

Q2: How do I determine pump efficiency?
A: Pump efficiency is typically provided by the manufacturer. Common values range from 0.5 to 0.85 for centrifugal pumps.

Q3: What is total dynamic head?
A: Total dynamic head is the total equivalent height that a fluid is to be pumped, accounting for static head, friction losses, and pressure differences.

Q4: Can I use this for viscous fluids?
A: This calculator is best for water-like fluids. For viscous fluids, additional correction factors are needed.

Q5: How do I select a motor size?
A: Motors are typically sized 10-25% larger than calculated HP to account for startup loads and safety factors.