Displacement is a geometric volume per revolution. It helps estimate pump delivery, but it is not the same as a guaranteed operating flow at every pressure, speed and temperature.
Calculate theoretical delivery
With displacement in cubic centimetres per revolution and speed in revolutions per minute, theoretical flow in litres per minute is displacement multiplied by speed, divided by 1,000. A 10 cm3/rev pump at 1,500 rpm gives 15 L/min theoretically.
Allow for volumetric losses
Actual outlet flow is lower because some fluid leaks internally. The difference depends on operating pressure, viscosity, speed and condition. Use the manufacturer's performance information for selection rather than assigning an arbitrary efficiency to every pump.
Check the full duty
The drive must provide sufficient torque and power, while the inlet must support the required flow. Minimum and maximum speed limits matter as well as displacement. A larger pump may overload the drive or increase idle heat if the circuit cannot use or unload the added delivery.
Practical checklist
- State displacement and speed rather than flow alone.
- Request delivery data at the expected pressure and fluid condition.
- Check drive capacity and inlet requirements together.
Discuss your application
Explore related hydraulic products, or send JIUDING your model code and application details. Include the circuit drawing and the operating conditions relevant to the checks above so the required configuration can be reviewed.
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