Calculator Inputs
Formula Used
The calculator starts with the standard pump flow relationship:
Theoretical flow (L/min) = displacement (cc/rev) × speed (rpm) ÷ 1000
Actual flow = theoretical flow × volumetric efficiency
Hydraulic power (kW) = flow (L/min) × pressure (bar) ÷ 600
Input power = hydraulic power ÷ mechanical efficiency
For cylinder speed, flow is converted to cubic meters per second. Then speed equals flow divided by piston area. Retract speed uses annulus area, which is bore area minus rod area.
How to Use This Calculator
- Choose whether you want to solve flow, displacement, or speed.
- Enter the known pump values and select the correct units.
- Add volumetric efficiency to include internal leakage.
- Enter working pressure and mechanical efficiency for power estimates.
- Add cylinder and line details if speed and velocity checks are needed.
- Press Calculate. The result appears above the form.
- Use CSV or PDF buttons to save a report.
Example Data Table
| Displacement | Speed | Efficiency | Actual Flow | Pressure | Hydraulic Power |
|---|---|---|---|---|---|
| 25 cc/rev | 1450 rpm | 88% | 31.9 L/min | 120 bar | 6.38 kW |
| 45 cc/rev | 1500 rpm | 90% | 60.75 L/min | 160 bar | 16.2 kW |
| 80 cc/rev | 1800 rpm | 92% | 132.48 L/min | 210 bar | 46.37 kW |
Hydraulic Pump Flow Guide
Why flow matters
Hydraulic flow controls actuator speed. It also affects heat, noise, and energy use. A pump can have the right pressure rating and still miss the needed cycle time. Flow should be checked with displacement, speed, and volumetric efficiency together. This calculator keeps those values visible, so a designer can test a pump before ordering parts.
Useful design checks
The first check is theoretical flow. It assumes every pump chamber fills and empties perfectly. Real pumps leak internally. Wear, fluid temperature, viscosity, and pressure all change that loss. Volumetric efficiency adjusts the ideal value into a closer working estimate. A high efficiency value fits a healthy pump. A low value can show wear or difficult operating conditions.
Pressure and power
Flow alone does not tell the required drive size. Pressure must be included. Hydraulic power rises when either flow or pressure rises. Input power is higher again because the pump needs mechanical allowance. This is why a small change in pressure can affect motor selection. Always leave a service margin when the machine has long duty cycles, shock loads, or hot oil.
Cylinder speed planning
Many flow problems appear as slow cylinders. Bore size changes extension speed. Rod size changes retract speed. A larger bore creates more force, but it needs more oil for the same travel. The calculator estimates both directions when cylinder values are entered. This helps compare speed targets against pump capacity.
Line velocity and service use
Pipe and hose size should also be checked. High velocity can increase pressure loss and heat. Low velocity may create bulky lines and extra cost. The line velocity result gives a quick screening value. Field technicians can use the CSV or PDF report to record a test, compare a replacement pump, or document a maintenance recommendation. The values are estimates. Confirm final selections with manufacturer curves, fluid limits, and safety rules.
Good input habits
Use measured speed when possible, not only nameplate speed. Enter the expected working pressure, not the relief valve maximum, unless checking worst case power. Keep unit choices consistent. Recheck results after changing oil grade, pump series, motor speed, or cylinder diameter. Small input errors can create large sizing differences quickly.
FAQs
What is hydraulic pump flow?
Hydraulic pump flow is the oil volume moved by the pump over time. It is usually shown in liters per minute or gallons per minute. Flow mainly controls actuator speed.
What values are needed for pump flow?
You need pump displacement, pump speed, and volumetric efficiency. Displacement shows oil moved per revolution. Speed shows revolutions per minute. Efficiency adjusts for internal leakage.
Why is actual flow lower than theoretical flow?
Actual flow is lower because real pumps leak internally. Clearances, pressure, wear, oil temperature, and viscosity all affect leakage. Volumetric efficiency estimates this loss.
Can this calculator estimate motor power?
Yes. Enter working pressure and mechanical efficiency. The tool calculates hydraulic power and estimated input power, so motor sizing can be reviewed with a service margin.
How does safety factor affect the result?
The safety factor raises the design flow used for power checks. It helps allow for margin, heat, aging, and changing duty conditions. Use a realistic value.
What is a good volumetric efficiency?
Healthy hydraulic pumps often have high volumetric efficiency, but the value depends on pump type and pressure. Use manufacturer data when available for better accuracy.
Can I calculate cylinder speed?
Yes. Enter bore, rod, and stroke values. The calculator estimates extension and retract speeds. Retract speed uses annulus area, not full bore area.
Are the exports generated on the same page?
Yes. The CSV and PDF buttons use the same entered values. They create simple reports that can be saved for design notes or maintenance records.