Pump Displacement (cm³/rev)
Displacement is the theoretical oil volume a pump sweeps in one full revolution, expressed in cm³/rev. To find flow rate, multiply displacement by speed and divide by 1000. On gear pumps in mobile equipment, typical values fall in the 4-40 cm³/rev range.
Displacement is a pump's identity; together with pressure rating it defines the pump. The math is simple: a 16 cm³/rev pump at 2000 rpm theoretically delivers 32 l/min. Actual flow falls below that by the volumetric efficiency; on a new gear pump typically around 90%, so about 29 l/min.
- Wear indicator: if measured flow at the same speed drops over time, internal leakage has increased. The drop becomes more pronounced as pressure rises.
- Wrong sizing: increasing displacement raises speed but raises the required drive power by the same proportion.
- Reservoir relation: tank volume should be at least half the per-minute flow rate.
This value continues to set the system's speed ceiling even after electronic lever control is added. Pushing the joystick all the way opens the lever fully; there is no speed beyond that, because the pump has already drawn the upper limit.
Where this term is used: What Is a Hydraulic Lever Retrofit Kit? Definition, Components, Operating Principle