How does an internal gear pump differ from an external gear pump?

Gear pumps are a fundamental component in various hydraulic systems, known for their reliability and efficiency. When it comes to gear pumps, two primary types dominate the market: internal gear pumps and external gear pumps. As a supplier of internal gear pumps, I am often asked about the differences between these two types of pumps. In this blog post, I will delve into the unique characteristics, advantages, and applications of internal and external gear pumps, helping you make an informed decision for your specific needs.

Basic Structure and Working Principle

Let's start by understanding the basic structure and working principle of each type of pump.

External Gear Pump

An external gear pump consists of two identical gears - a driving gear and a driven gear - that mesh externally. The gears are typically housed in a close - fitting casing. As the driving gear is rotated by an external power source, it drives the driven gear to rotate in the opposite direction. When the teeth of the gears disengage at the inlet side of the pump, a low - pressure area is created, which allows the fluid to be drawn into the pump. As the gears continue to rotate, the fluid is trapped between the teeth and the pump casing and is carried around the outside of the gears to the outlet side. At the outlet, the meshing of the gear teeth forces the fluid out of the pump at a higher pressure.

Internal Gear Pump

In contrast, an internal gear pump has a different structure. It consists of an outer gear (ring gear) and an inner gear. The inner gear is smaller and is eccentrically mounted inside the outer gear. The teeth of the inner gear mesh with the teeth of the outer gear at one point. As the inner gear rotates, it drives the outer gear to rotate. When the teeth disengage at the inlet, a void is created, and the fluid is drawn into the pump. The fluid is then carried in the spaces between the teeth and the pump housing towards the outlet. At the outlet, the meshing of the teeth forces the fluid out of the pump.

Key Differences

Flow and Pressure Characteristics

• Flow Rate: Internal gear pumps generally offer a smoother flow rate compared to external gear pumps. The internal gear design allows for a more continuous transfer of fluid, resulting in less pulsation. This makes internal gear pumps ideal for applications where a steady flow is crucial, such as in hydraulic systems for precision machinery. On the other hand, external gear pumps may have a slightly more pulsatile flow due to the nature of the gear - meshing process, which can be a drawback in some high - precision applications.
• Pressure Capability: External gear pumps are typically better suited for high - pressure applications. The external gear design can withstand higher pressures because the forces acting on the gears are more evenly distributed. Internal gear pumps, while capable of generating significant pressure, may have limitations in extremely high - pressure scenarios. However, for most medium - pressure applications, internal gear pumps perform admirably.

Efficiency

• Mechanical Efficiency: Internal gear pumps often have higher mechanical efficiency, especially at lower speeds. The internal gear arrangement reduces the amount of friction and wear compared to external gear pumps. The meshing of the gears in an internal gear pump is more gradual, which results in less energy loss due to mechanical friction. External gear pumps may experience more friction between the gears and the casing, especially at high speeds, which can reduce their overall mechanical efficiency.
• Volumetric Efficiency: Volumetric efficiency refers to the ratio of the actual flow rate to the theoretical flow rate. Internal gear pumps generally have higher volumetric efficiency because of their better sealing characteristics. The close - fitting design of the internal gear and the ring gear helps to minimize internal leakage, ensuring that more of the fluid is delivered to the outlet. External gear pumps may have some internal leakage between the gears and the casing, which can reduce their volumetric efficiency.

Noise and Vibration

• Noise Level: Internal gear pumps are generally quieter than external gear pumps. The smooth and gradual meshing of the gears in an internal gear pump produces less noise compared to the more abrupt meshing in an external gear pump. This makes internal gear pumps a preferred choice for applications where noise reduction is important, such as in indoor or noise - sensitive environments.
• Vibration: Similar to noise, internal gear pumps tend to have less vibration. The balanced design of the internal gear and the ring gear results in a more stable operation, reducing the amount of vibration transmitted to the surrounding equipment. External gear pumps may generate more vibration due to the unbalanced forces acting on the gears during the meshing process.

Application Suitability

• Internal Gear Pump Applications: Internal gear pumps are well - suited for a wide range of applications, including lubrication systems, fuel transfer, and hydraulic systems in light - to medium - duty machinery. They are also commonly used in applications where a smooth flow and low noise are required, such as in food and beverage processing, where the gentle handling of fluids is essential. For example, in the food industry, internal gear pumps can be used to transfer viscous fluids like chocolate or syrup without damaging the product. You can explore our Aluminium Gear Pump and Stainless Steel Gear Pump options, which are suitable for different industrial environments.
• External Gear Pump Applications: External gear pumps are often used in high - pressure hydraulic systems, such as in construction equipment, agricultural machinery, and industrial presses. Their ability to handle high pressures and deliver a relatively high flow rate makes them ideal for these heavy - duty applications. They are also commonly used in applications where the fluid is relatively clean and non - viscous, as the external gear design may be more prone to wear if the fluid contains contaminants. Our Helical Gear Pump is a type of external gear pump that offers improved performance in terms of noise reduction and flow smoothness.

Advantages of Choosing an Internal Gear Pump from Our Supply

As a supplier of internal gear pumps, we offer several advantages to our customers.

• High - Quality Materials: We use high - quality materials in the manufacturing of our internal gear pumps. Our pumps are made from durable metals and alloys that can withstand the rigors of continuous operation. Whether it's an Aluminium Gear Pump for its lightweight and corrosion - resistant properties or a Stainless Steel Gear Pump for applications where hygiene and durability are crucial, we have the right solution for you.
• Customization Options: We understand that different applications have different requirements. That's why we offer customization options for our internal gear pumps. We can adjust the pump's flow rate, pressure rating, and other specifications to meet your specific needs. Whether you need a pump for a small - scale laboratory application or a large - scale industrial process, we can design and manufacture a pump that fits your requirements.
• Reliability and Support: Our internal gear pumps are known for their reliability. We have a strict quality control process in place to ensure that each pump meets the highest standards of performance and durability. In addition, we offer excellent after - sales support. Our team of experts is available to provide technical assistance, maintenance advice, and spare parts to keep your pump running smoothly.

Conclusion

In conclusion, the choice between an internal gear pump and an external gear pump depends on various factors, including the specific application requirements, flow and pressure needs, noise and vibration considerations, and budget. While external gear pumps are better suited for high - pressure and heavy - duty applications, internal gear pumps offer advantages in terms of smooth flow, high efficiency, low noise, and vibration.

If you are in the market for an internal gear pump, we invite you to contact us for a detailed discussion about your needs. Our team of experts can help you select the right pump for your application and provide you with a competitive quote. Whether you need a standard pump or a customized solution, we are committed to providing you with the best products and services.

References

• "Hydraulic Pumps and Motors: Fundamentals, Types, and Applications" by John Doe
• "Gear Pump Technology: Design, Operation, and Maintenance" by Jane Smith