In a centrifugal pump system, "head" is far more than just a technical parameter—it directly determines whether the pump can deliver fluid to the target location and effectively overcome pipeline resistance. Errors in head calculation can lead to insufficient flow rate and increased energy consumption at best, and cavitation, motor overload, or even equipment damage at worst.
Whether you are designing a new system, replacing an old pump, or troubleshooting operational abnormalities, mastering accurate head calculation methods is key to achieving efficient, stable, and energy-saving operation. This article breaks down complex principles into clear steps, making it easy to grasp even without a deep background in fluid mechanics.
Head refers to the total mechanical energy provided by a centrifugal pump to a unit weight of fluid, with units of meters (m) or feet (ft).
Note: Head ≠ Pressure! Although they can be converted using formulas, their physical meanings are different:
Head consists of four components:
| Component | Description |
|---|---|
| Static Head | Vertical height difference between the suction liquid level and the discharge liquid level (Unit: m) |
| Pressure Head | Equivalent liquid column height required to overcome the pressure difference between the suction side and the discharge side |
| Velocity Head | Kinetic energy term generated by the fluid flow velocity (usually small, but needs to be considered in specific cases) |
| Friction Head | Energy loss caused by friction of fluid in pipes, valves, and elbows |
✅ Total Head Formula:Htotal = Hstatic + Hpressure + Hvelocity + Hfriction
Transporting room-temperature water from an open suction tank to a pressurized discharge tank with the following known conditions:
💡 Note: The pressure of an open tank is atmospheric pressure, with a gauge pressure of 0, so the suction side pressure head is 0.
Assuming the cross-sectional area of the suction tank is much larger than that of the pipe, the suction flow velocity ≈ 0, so only the discharge side velocity head needs to be calculated.
Pipe cross-sectional area:A = π(d/2)² = 3.1416 × (0.05)² ≈ 0.00785 m²
Flow velocity:v = Q/A = 0.0139 / 0.00785 ≈ 1.77 m/s
Velocity Head:Hvelocity = v²/(2g) = (1.77)²/(2×9.81) ≈ 3.13 / 19.62 ≈ 0.16 m
⚠️ Note: If the suction and discharge pipe diameters are different, the velocity difference should be calculated: (v₂² - v₁²)/(2g)
Using the Darcy-Weisbach formula:Hfriction = f × (L/d) × (v²/(2g))
Substitute the data:
Hfriction = 0.02 × (100/0.1) × 0.16 = 0.02 × 1000 × 0.16 = 3.2 m
✅ Important Reminder:The original text incorrectly calculated the result as 32 m; the actual value should be 3.2 m. This error will lead to a seriously oversized pump selection, resulting in waste!
🔧 Tip: The 100 m pipe length should include the "equivalent length" of valves and elbows (e.g., one 90° elbow ≈ 3 m of straight pipe).
Htotal = Hstatic + Hpressure + Hvelocity + Hfriction = 15 + 20.4 + 0.16 + 3.2 = 38.76 m
📌 Engineering Recommendation: Reserve a 5%~10% margin when selecting a pump. It is recommended to choose a centrifugal pump with a rated head ≥ 40~42 m.
| Tool | Purpose |
|---|---|
| Moody Chart | Accurately determine the friction factor f based on the Reynolds number and pipe wall roughness |
| Fitting Equivalent Length Table | Convert elbows, valves, etc., into straight pipe lengths for inclusion in Hf calculation |
| Online Calculators | Such as Engineering ToolBox, Pump-Flo, for quick result verification |
| On-Site Pressure Gauge Method | For existing systems, the head can be back-calculated using the formula:H = (Pd - Ps)/(ρg) + Δz + (vd² - vs²)/(2g) |
| Misconception | Correct Understanding |
|---|---|
| ❌ "Head is pressure" | ✅ Head is energy height (m), pressure is force (bar); Conversion formula: H = P/(ρg) |
| ❌ Ignoring friction loss | ✅ In long pipelines or small-diameter pipes, Hf can account for more than 20% of the total head |
| ❌ Omitting velocity head | ✅ Cannot be ignored in small-diameter, high-flow-rate systems (especially when suction/discharge pipe diameters are different) |
| ❌ Using the distance between pump inlet and outlet instead of liquid level height difference | ✅ Static head must be the vertical distance between liquid levels |
| ❌ Using water density when transporting oil products | ✅ For non-aqueous fluids, the calculation should be corrected according to the actual density ρ and viscosity ν |
Centrifugal pump head calculation is not an insurmountable challenge—as long as it is broken down into four parts: static head, pressure head, velocity head, and friction head, and parameters are substituted step by step, reliable results can be obtained. As a professional brand in the industrial fluid equipment field, Teffiko's centrifugal pump series products are designed based on rigorous fluid mechanics, accurately matching head requirements in different scenarios, and featuring high energy efficiency ratio and stable durability, perfectly meeting the selection and implementation needs after head calculation. For more details on Teffiko's centrifugal pump products suitable for different working conditions or to obtain customized selection solutions, please feel free to contact us!
