Internal Gear Pumps

Understanding the Working and Construction of Internal Gear Pumps

Internal gear pumps are the one of important components in various industries. Internal gear pumps are known for fluid handling applications, due to their efficiency and reliability.

Construction details of Internal Gear Pumps

Understanding the construction of internal gear pumps helps in increasing their durability and efficiency. Key construction features include:

  1. Gears: The external gear has more teeth than the internal gear, due to this internal gear rotates faster while maintaining engagement. This design ensures smooth operations and less wear and tear.
  2. Housing: The pump housing is carefully designed to ensure proper alignment of the gears and to minimize leakage. Housing is generally made from materials such as cast iron, stainless steel, or aluminum, depending on the application.
  3. Seals and Bearings: Seals and bearings are installed to prevent leakage and ensure smooth running, High-quality seals and bearings are important for maintaining efficiency and preventing contamination of the fluid.
  4. Mounting: This type of pump can be mounted in horizontal or vertical positions depending upon space and operational requirements.

Working Principles of Internal Gear Pumps:

Internal gear pumps are positive displacement pumps, it’s delivered a fixed amount of volumetric fluid with each revolution of the pump.

Hydraulic fluid enters the pump housing through an inlet port. As the gears rotate, fluid is drawn into the expanding cavities formed between the teeth of the gears due to low pressure. The crescent shape of the gear teeth divides the fluid and acts as a seal between the suction and discharge ports.

The rotating gears then carry the fluid from the inlet port to the outlet port of the pump. The meshing gears and the shape of the pump housing ensure that fluid is displaced positively without relying on centrifugal force.

This process is continuous as long as the gears are turning, providing a consistent flow rate and pressure.


Internal gear pumps offer several advantages that make them suitable for a wide range of applications:

  • High Efficiency: They operate efficiently across a range of viscosities, making them ideal for handling both thin and thick fluids.


  • Reliability: With fewer moving parts and positive displacement operation, internal gear pumps are known for their reliability and long service life.
  • Versatility: They are used in hydraulic systems, fuel transfer, lubrication systems, and other industrial applications where precise fluid handling is critical.
  • High-Viscosity:  Internal gear pump is excellent for high-viscous fluid.


There are a few disadvantages of Internal gear pumps:

  • Suitable for medium speeds.
  • Internal gear pump was used for medium pressure.
  • In the shaft bearing there is an overhung load.

Maintenance Tips

To ensure optimal performance and longer life of internal gear pumps, regular maintenance is essential. This includes:

  • Inspection of wear and tear: Scheduled inspections of wear and tear of gear teeth.
  • Seal Inspection: Ensuring seals are intact and not leaking.
  • Fluid Quality: Using clean fluids and filtering as necessary to prevent contamination.

In conclusion, internal gear pumps are versatile and reliable devices essential in various industrial processes. Understanding their working principles and construction details helps in appreciating their functionality and choosing the right pump for specific applications. For more detailed information, consult technical resources or speak with a pump specialist to ensure optimal pump selection and performance in your operations.

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