A centrifugal pump impeller size chart helps select the correct impeller diameter for desired flow rate, head (pressure), and efficiency. Since impeller sizing varies by pump model and manufacturer, here’s a general guide along with key considerations.
1. How Impeller Size Affects Pump Performance
Diameter (D) ↑ → Flow (Q) ↑, Head (H) ↑, Power (P) ↑
Trimming an impeller (reducing D) lowers performance but improves efficiency at partial loads.
Affinity Laws (for centrifugal pumps)
| Change | Flow (Q) | Head (H) | Power (P) |
|---|---|---|---|
| Speed (N) change | Q2=Q1×N1N2 | H2=H1×(N1N2)2 | P2=P1×(N1N2)3 |
| Impeller (D) change | Q2=Q1×D1D2 | H2=H1×(D1D2)2 | P2=P1×(D1D2)3 |
2. Typical Impeller Diameter Ranges by Pump Type
| Pump Type | Impeller Size Range (Diameter) | Common Applications |
|---|---|---|
| End-Suction Pumps | 2" – 16" (50mm – 400mm) | Water supply, HVAC, irrigation |
| Multistage Pumps | 4" – 12" (100mm – 300mm) per stage | High-pressure boosting, boiler feed |
| Submersible Pumps | 3" – 14" (75mm – 350mm) | Drainage, sewage, wells |
| API Process Pumps | 6" – 20" (150mm – 500mm) | Oil & gas, chemical processing |
| Self-Priming Pumps | 5" – 12" (125mm – 300mm) | Construction, dewatering |
3. Example: Performance Chart for a 6x4 End-Suction Pump
(Flow in GPM, Head in ft, Impeller in inches)
| Impeller Ø (in) | Max Flow (GPM) | Max Head (ft) | HP Required |
|---|---|---|---|
| 10.0" | 800 | 150 | 15 HP |
| 9.5" | 700 | 135 | 12 HP |
| 9.0" | 650 | 120 | 10 HP |
| 8.5" | 600 | 105 | 7.5 HP |
| 8.0" | 550 | 90 | 5 HP |
*(Note: Exact values depend on pump model & speed [1750/3500 RPM])*
4. How to Select the Right Impeller Size?
Check the pump curve (provided by the manufacturer).
Determine required flow (Q) & head (H) for your system.
Match performance – Find where Q & H intersect on the curve.
Trim impeller if needed (max 75% of original diameter).
Impeller Trimming Rules:
Do not exceed manufacturer’s max trim limit (usually 15-25% reduction).
Avoid trimming below minimum size (causes cavitation & inefficiency).
Re-balance impeller if trimmed significantly.
5. Common Impeller Sizing Mistakes
❌ Oversizing → Wasted energy, cavitation risk.
❌ Undersizing → Inadequate flow/pressure.
❌ Ignoring NPSH requirements → Cavitation damage.
6. Where to Find Manufacturer-Specific Charts?
Goulds, Grundfos, ITT, Sulzer, KSB – Check technical manuals.
Hydraulic Institute (HI) Standards – General guidelines.
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