Gerotor pump work on the principle of internal gear pump by using gear shaped rotor elements meshing internally.

A gerotor pump is a type of positive displacement pump that uses the interaction of rotating gears to pump fluid. It consists of an outer gear (rotor) and an inner gear (idler) that mesh together to create chambers. As the gears rotate, the fluid is trapped in the chambers and carried from the suction side to the discharge side of the pump.


Gerotor pump  is a positive displacement pump. The name gerotor is derived from “generated rotor”. A gerotor unit have an inner and outer rotor. The inner rotor has n teeth, while the outer rotor has n+1 teeth.The axis of the inner rotor is offset from the axis of the outer rotor. These both rotors rotate on their respective axes.

It consists of following parts :
1) Outer ring : The outer ring is a casing in which gerotor pair is mounted.
2) Outer gerotor : Outer gerotor is idler and it has always one tooth more than inner gerotor.
3) Inner gerotor : The inner gerotor is the driver. The number of teeth of the outer and inner gerotor vary. The axis of inner gerotor is offset from the axis of the outer gerotor.
4) Suction and discharge port : The suction and discharge ports are provided to suck and deliver oil respectively.
gerotor pump


  • When inner gerotor rotates with the help of motor, it creates partial vaccum near the suction portwhen mesh with the outer gerotor. The oil enters through the suction port.
  • If the number of teeth for the inner and outer gerotor are  four and five respectively, then while the inner gerotor makes one revolution, the outer one makes only 4/5 revolution.
  • Due to offset movement between inner and outer gerotor, the volume near the delivery port decreases and oil is forced out through delivery port.
  • The care should be taken as gerotor are to be manufactured with high precision otherwise internal leakage becomes excessive.
  • It can operate at the pressure of 125bar, maximum speed of 2000-3600 rpm with maximum discharge of 200 lit/min.


  • General mechanical and plant engineering
  • Shipbuilding and offshore industry
  • Paper, printing, and pulp industries
  • Heavy  industry

Materials used for pump Construction

  • Externals (head, casing) – Cast iron
  • Internals (rotor, idler) – Steel
  • Bushing – Carbon graphite, bronze, and other materials as needed
  • Shaft Seal – Lip seals, component mechanical seals


  • Constant and even discharge
  • Operates well in either direction
  • Quiet operation

The gerotor pump design offers several advantages and characteristics:

  1. Compact Size: Gerotor pumps are known for their compact size, making them suitable for applications where space is limited. Their small footprint allows for easy integration into various systems.
  2. High Efficiency: Gerotor pumps are highly efficient due to the tight clearances between the gears. This design minimizes internal leakage, resulting in improved volumetric efficiency and reduced energy consumption.
  3. Self-Priming Capability: Gerotor pumps have excellent self-priming capabilities, meaning they can draw fluid into the pump without the need for external priming. This feature is beneficial for starting the pump and ensuring continuous operation.
  4. Versatile Fluid Compatibility: Gerotor pumps can handle a wide range of fluids, including liquids with low to moderate viscosities. They are commonly used for pumping oils, fuels, lubricants, hydraulic fluids, and other industrial fluids.
  5. Smooth Flow and Low Pulsation: Gerotor pumps provide a steady and uniform flow of fluid, minimizing pulsations and pressure variations. This makes them suitable for applications that require precise flow control and consistent fluid delivery.
  6. Relatively Low Noise and Vibration: Gerotor pumps operate at relatively low noise and vibration levels due to the meshing action of the gears and the close tolerances maintained between them. This characteristic is beneficial in noise-sensitive environments.

Despite their advantages, gerotor pumps also have some limitations:

  1. Limited Operating Speed Range: Gerotor pumps typically have a limited range of operating speeds. High rotational speeds can generate heat, increase wear, and reduce the pump’s overall efficiency and lifespan.
  2. Sensitivity to Contaminants: Gerotor pumps can be sensitive to particulate contaminants present in the fluid being pumped. Abrasive particles can cause wear on the gear surfaces, leading to reduced performance and potential damage.
  3. Limited Pressure Capability: Gerotor pumps may have limitations in terms of the maximum pressure they can handle. Operating at excessively high pressures can cause increased leakage and potential failure.
  4. Maintenance and Service Requirements: Gerotor pumps require proper maintenance, including regular inspection and lubrication. The tight clearances between gears make it important to ensure clean and adequate lubrication to minimize wear and maintain optimal performance.
  5. Cost: Depending on the design and quality, gerotor pumps can be relatively more expensive compared to other types of pumps. The complex gear profiles and tight tolerances involved in their manufacturing contribute to their higher cost.


  • What is the principle of gerotor pump?
  • It work on the principle of internal gear pump by using gear shaped rotor elements meshing internally.
  • What is the advantages of gerotor pump?
  • Constant and even discharge.    Operates well in either direction.     It has quiet operation.
  • What type of pump is Gerotor pump?
  • Gerotor pump is a positive displacement pump.
  • What is the pressure of gerotor pump?
  • It can operate at the pressure of 125bar, maximum speed of 2000-3600 rpm with maximum discharge of 200 lit/min.
  • Are gerotor pumps self priming?
  • It’s depend on pump manufacturer. Some gerotor pump like SKF product series 143 are self-priming, positive-displacement pumps with fixed displacement and high efficiency.
  • What is the application of gerotor pump?
  • It is suitable for General mechanical and plant engineering, heavy industries, etc.
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By Aditya

Hi, I’m Aditya Sharma, a professional blogger from Gurgaon, India and I launched this blog called aadityacademy on July 2021. is a mechanical Project-oriented platform run by Aditya sharma and I got the motivation to start aadityacademy blog after seeing less technical education information available on google.

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