Hidroteknik Calculators
Gear Pump Selection
To pick the right gear pump you need three things: the required flow, the motor speed, and the working pressure. From these the required displacement is found.
⚙ Open the Hydraulic Calculator →Required Displacement
Q: required flow (L/min), n: speed (rpm), ηv: volumetric efficiency (≈0.90–0.95), Vg: cc/rev
Units
| Quantity | Symbol | Unit |
|---|---|---|
| Flow | Q | L/min |
| Speed | n | rpm |
| Volumetric efficiency | ηv | – (0.90–0.95) |
| Displacement | Vg | cc/rev |
Worked Example
Given: Required flow Q = 40 L/min, motor speed n = 1450 rpm, volumetric efficiency ηv = 0.92.
1) Displacement: Vg = 40 × 1000 / (1450 × 0.92) = ≈ 30 cc/rev
2) Choose the nearest standard displacement (e.g. 30 cc/rev)
3) Verify the pump's pressure class covers the working pressure
Frequently Asked Questions
How is pump displacement selected?
From the required flow and speed via Vg = Q×1000/(n×ηv), then round up to the nearest standard displacement.
Why does the pressure class matter?
Every pump has a maximum continuous/intermittent working pressure. Your system pressure must stay below that limit.
How does speed affect the pump?
Flow is proportional to speed. The same displacement gives more flow at higher rpm, but you must respect the manufacturer's min/max speed limits.