Hidroteknik Calculators
Hydraulic Pump Flow Rate Calculation
A hydraulic pump's flow rate depends on its displacement (volume per revolution) and its speed. Volumetric efficiency brings the actual flow slightly below the theoretical value.
⚙ Open the Hydraulic Calculator →Flow Formula
Theoretical flow
Vg: displacement (cc/rev), n: speed (rpm), Q: L/min
Actual flow
ηv: volumetric efficiency (typically 0.90–0.97)
Units
| Quantity | Symbol | Unit |
|---|---|---|
| Displacement | Vg | cc/rev |
| Speed | n | rpm |
| Flow | Q | L/min |
| Volumetric efficiency | ηv | – (0.90–0.97) |
Worked Example
Given: Displacement Vg = 32 cc/rev, speed n = 1450 rpm, volumetric efficiency ηv = 0.95.
1) Theoretical flow: Q = 32 × 1450 / 1000 = 46.4 L/min
2) Actual flow: Q = 46.4 × 0.95 = 44.1 L/min
Frequently Asked Questions
What is pump displacement?
Displacement (Vg) is the oil volume the pump delivers per full revolution (cc/rev). It is the primary driver of flow.
Why does volumetric efficiency matter?
Internal leakage makes actual flow lower than theoretical. Volumetric efficiency (0.90–0.97) accounts for this difference.
How does speed affect flow?
Flow is directly proportional to speed: doubling the rpm roughly doubles the flow.