Pump Horsepower 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)

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 specified 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 (gallons per minute, GPM)
\( H \) — Total dynamic head (feet, ft)
\( SG \) — Specific gravity of the fluid (dimensionless, 1 for water)
\( \eta \) — Pump efficiency (decimal between 0 and 1)
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 the actual power needed.

3. Importance of Pump Horsepower Calculation

Details: Proper horsepower calculation ensures correct pump selection, prevents underpowered or oversized pumps, and helps optimize energy consumption in fluid systems.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1 for water), and pump efficiency as a decimal (e.g., 0.85 for 85%). 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 4°C. Water has SG=1, while heavier fluids have SG>1 and lighter ones have SG<1.

Q2: What is typical pump efficiency?
A: Centrifugal pumps typically range from 50-85% efficiency, with higher efficiency in larger, well-designed pumps operating near their best efficiency point.

Q3: How does head relate to pressure?
A: Head (in feet) can be converted to pressure (in psi) by multiplying by SG and dividing by 2.31 (for water: 100 ft head ≈ 43.3 psi).

Q4: What if my flow is in m³/h instead of GPM?
A: Convert m³/h to GPM by multiplying by 4.403. 1 m³/h ≈ 4.403 GPM.

Q5: Should I add a safety factor to the calculated HP?
A: Yes, it's common practice to add 10-20% safety margin to account for system uncertainties and future expansion.