External Gear Pumps: Working Principle, Applications, and Practical Examples

External Gear Pumps: Working Principle, Applications, and Practical Examples

When it comes to rotary pumps, one of the most widely used designs is the external gear pump. Known for its simplicity, reliability, and efficiency, this pump plays a crucial role in industries ranging from hydraulics to chemical processing. In this Blog, we’ll explore how external gear pumps work, their advantages, practical examples, and why they remain a popular choice in engineering systems.

What is an External Gear Pump?

An external gear pump is a type of positive displacement pump that uses two gears rotating inside a casing to move fluid.  

- One gear is the power gear, driven by a motor.  

- The other is the idler gear, which rotates because of the power gear.  

- Fluid is trapped between the gear teeth and the pump casing, carried around, and discharged at the outlet.  

- The meshing of the gears prevents fluid from leaking back into the suction side.

How Does an External Gear Pump Work?

1. Suction Phase – Fluid enters the pump and is picked up by the rotating gear teeth.  

2. Trapping Phase – Fluid gets trapped in the cavities between the gear teeth and casing.  

3. Transfer Phase – As gears rotate, the trapped fluid is carried around the casing.  

4. Discharge Phase – The meshing of gears forces the fluid out through the discharge port, ensuring no backflow.

Practical Example

Imagine a hydraulic system in an excavator:  

- The external gear pump draws hydraulic oil from the reservoir.  

- It delivers pressurized oil to the hydraulic cylinders.  

- This enables the excavator arm to lift heavy loads smoothly.  

Another example is in lubrication systems of industrial machinery, where external gear pumps ensure a steady supply of oil to bearings and moving parts.

Advantages of External Gear Pumps

- High efficiency for handling viscous fluids.  

- Compact design with fewer moving parts.  

- Reliable sealing due to gear meshing.  

- Cost-effective compared to other pump types.  

- Versatile applications in hydraulics, lubrication, and chemical transfer.

Applications

- Hydraulic systems in construction equipment.  

- Lubrication pumps in engines and compressors.  

- Chemical transfer pumps for oils, solvents, and polymers.  

- Fuel pumps in automotive and aerospace industries.  

Conclusion

The external gear pump is a cornerstone of fluid handling technology. Its simple design, reliable operation, and wide range of applications make it indispensable in modern engineering. Whether in hydraulic excavators, lubrication systems, or chemical plants, external gear pumps continue to prove their value.