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What is the Impact of Viscosity on External Gear Pump and Internal Gear Pump Selection?
2026-05-09
Trustech
39
Gear pumps play a pivotal role in various industrial applications, ensuring the efficient transfer of fluids with precision and reliability. Among the various materials used in manufacturing gear pumps, aluminum stands out for its unique combination of strength, durability, and lightweight properties. This article explores the impact of viscosity on the selection between external gear pumps and internal gear pumps, helping you make informed decisions when choosing the right gear pump for your specific needs.
Understanding Gear Pumps
External Gear Pumps
Design and Working Principle:External gear pumps consist of two gearsa driving gear and a driven gearthat rotate in opposite directions. As the gears mesh, they create a sealed chamber between them, effectively transferring the fluid from the inlet to the outlet. This pump design is known for its simplicity and reliability in fluid transfer applications.
Advantages:- Stability and Consistency: External gear pumps are known for their consistent flow rate and stability, making them ideal for industries requiring precise fluid transfer.
- Low Maintenance: These pumps have fewer moving parts, reducing maintenance requirements.
- High Efficiency: They operate efficiently and can handle a wide range of fluids.
Disadvantages:- Limited Viscosity Range: External gear pumps are typically less effective with very high viscosity fluids due to increased power consumption and wear on the gears.
Common Applications:External gear pumps are widely used in industries where consistent and smooth fluid flow is crucial, such as hydraulic systems, lubrication systems, and chemical processing.
Internal Gear Pumps
Design and Working Principle:Internal gear pumps feature a unique design with an inner gear rotating within an outer gear, unlike the external gear pump design. This configuration draws fluid into the pump through the inlet and forces it through the pump to the outlet as the gears mesh.
Advantages:- Versatility: Internal gear pumps can handle a wide range of viscosities, making them suitable for applications in industries like food processing, pharmaceuticals, and petrochemicals.
- Uniform Shear Stress: These pumps provide uniform shear stress on the fluid, reducing degradation of sensitive fluids.
- Robust: They handle high viscous fluids better than external gear pumps due to their design.
Disadvantages:- Higher Maintenance: Internal gear pumps have more moving parts, which can require more frequent maintenance.
Common Applications:Internal gear pumps are suitable for applications where fluid viscosity can vary widely, such as in food processing, pharmaceuticals, and petrochemicals.
Impact of Viscosity on Gear Pumps
Viscosity and Performance
Viscosity Definition:Viscosity is a fluid's resistance to flow. Higher viscosity fluids are thicker and more resistant to flow, while lower viscosity fluids are thinner and more easily flowable.
Impact on Flow Rate and Efficiency:Higher viscosity fluids require more power to move through the pump, leading to higher power consumption and potential energy inefficiencies. Moreover, higher viscosity fluids can increase resistance within the pump, leading to reduced efficiency and wear on mechanical components.
External Gear Pumps
Viscosity Limits:External gear pumps are best suited for fluids with viscosities ranging from 2 to 1500 centistokes. For very high viscosity fluids (above 1500 centistokes), external gear pumps may experience higher power requirements and increased wear on gears.
Applications:- Hydraulic Systems: Suitable for fluids with moderate viscosity.
- Lubrication Systems: Commonly used for oils with medium viscosity.
- Chemical Processing: Used for transfer of chemical solutions with low to medium viscosity.
Internal Gear Pumps
Viscosity Limits:Internal gear pumps excel with higher viscosities, making them ideal for fluids with viscosities up to 2,000,000 centistokes. This range offers more versatility, especially in industries where the fluid's viscosity can vary significantly.
Applications:- Food Processing: Ideal for high viscosity fluids such as sauces, pastes, and creams.
- Pharmaceuticals: Suitable for handling viscous medications and suspensions.
- Petrochemicals: Effective for transferring oils and lubricants in automotive and industrial applications.
| Gear Pump Type | Viscosity Range (Centistokes) | Advantages | Common Applications |
|---|---|---|---|
| External Gear | 2 - 1500 | Stable flow rate, low maintenance | Hydraulic systems, lubrication systems, chemical processing |
| Internal Gear | 2 - 2,000,000 | High viscosity capability, uniform shear stress | Food processing, pharmaceuticals, petrochemicals |
How to Select the Right Gear Pump
Factors to Consider
Fluid Properties:- Viscosity: Higher viscosity fluids are better suited for internal gear pumps.
- Shear Sensitivity: Sensitive fluids require internal gear pumps to maintain consistency.
Pressure Requirements:- Operating Pressure: Ensure the pump can handle the required operating pressure.
Flow Rate:
- Capacity: Determine the required flow rate based on your application's needs.
Tips for Choosing Between External and Internal Gear Pumps
High Viscosity Oil:- High Viscosity: Internal gear pumps are better suited for high viscosity oils due to their design.
- Temperature: Consider the temperature range required for your application.
Membrane Production:- Consistency: Internal gear pumps provide better uniformity, making them ideal for applications requiring precise fluid control.
Conclusion
In summary, knowing the impact of viscosity on external and internal gear pump performance is crucial when selecting the right pump for your application. External gear pumps are excellent for low to medium viscosity fluids, while internal gear pumps excel with higher viscosity fluids.
For applications involving high viscosity fluids, such as food processing and petrochemicals, internal gear pumps offer greater versatility and efficiency. By considering the viscosity range, pressure requirements, and specific fluid properties, you can make an informed decision that matches your needs.
Shanghai Trustech, with over a decade of experience in fluid handling and pump applications, can provide expert advice and cutting-edge solutions to help you choose the right gear pump for your needs. If you have any questions or require further assistance, feel free to reach out to our team.
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