Understanding the Construction and Working Mechanism of Internal Gear Pumps

Internal gear pumps are widely used in various industries for their ability to handle thick and viscous fluids efficiently. This article delves into the intricate construction and working mechanism of internal gear pumps, providing a comprehensive understanding of their components and operational principles.

Introduction

An internal gear pump is a type of pump that uses the rotary displacement mechanism to move fluids reliably. These pumps are essential in many industrial applications due to their efficiency, reliability, and ability to handle different types of fluids, including thick and viscous substances such as oil, syrup, and asphalt. Understanding the construction and working of internal gear pumps is crucial for engineers and technicians working across various industries.

Basic Components of Internal Gear Pumps

To comprehend the internal gear pump's mechanism, it is essential to understand its basic components:

Rotor and Idler Gears

• Rotor (Outer Gear): The larger gear that is driven by a motor.
• Idler (Inner Gear): The smaller gear that meshes with the rotor.

Together, these gears create a vacuum at the inlet, drawing fluid into the pump, and then compressing it to force it out of the discharge port. The rotor and idler gears are precision machined to ensure proper meshing and minimal fluid leakage.

Crescent Seal

In some designs, a crescent-shaped seal (or divider) fits between the rotor and idler gears. This seal separates the suction and discharge areas, guiding the fluid and preventing it from flowing back into the inlet. This design is crucial for maintaining a smooth and continuous flow of fluid.

Pump Casing

The pump casing houses and protects all the internal components. The casing can be made of durable materials such as cast iron, stainless steel, or aluminum, depending on the specific application and the fluid being pumped. The casing must be robust enough to withstand the pressure and temperature generated during operation while ensuring a long service life.

Bearings and Seals

• Bearings: These support the rotation of the gears and prevent excessive wear. Precision bearings are used to ensure smooth and efficient operation.
• Seals: Various types of seals, such as lip seals or O-rings, prevent leakage between the components. High-quality seals are necessary to maintain the pump's efficiency and prevent contamination.

Construction Details

The construction of internal gear pumps involves several key components:

Materials Used

• Stainless Steel: Often used in highly corrosive environments due to its resistance to rust and corrosion. Stainless steel provides longevity and durability.
• Cast Iron: A common material for pump casings due to its strength and cost-effectiveness. Cast iron can withstand high pressures and temperatures.
• Ceramic or Carbon: Used in advanced applications where wear resistance is crucial. These materials offer excellent wear resistance and operational reliability.

Customization options are available to tailor the pump to specific requirements. For example, Shanghai Trustech Technology can provide pumps with custom materials like PTFE seals for handling corrosive fluids, ensuring a longer service life and reliable operation.

Customization Services

Trusted manufacturers like Shanghai Trustech Technology offer customization services, allowing users to select specific flow rates, pressures, and materials. Customization options ensure that the pump meets the exact needs of the application, providing a tailored solution for each use case.

Working Principle

The working principle of an internal gear pump involves a rotary positive displacement mechanism, which ensures a steady and continuous flow of fluid.

Positive Displacement Mechanism

The internal gear pump operates based on the positive displacement principle. As the rotor turns, it creates a vacuum at the inlet, pulling fluid into the pump. The meshing of the rotor and idler gears traps the fluid between the teeth, compressing it and pushing it out of the discharge port.

Operation Cycle

1. Suction Phase:
2. As the rotor and idler mesh apart, they create a vacuum that draws fluid into the suction port.

3. The crescent seal (if present) helps guide the fluid and prevent backflow.

4. Compression Phase:

5. As the gears mesh back together, the spaces between the teeth reduce, compressing the captured fluid and pushing it toward the discharge port.

6. The fluid is forced out of the discharge port under pressure.

7. Discharge Phase:

   
   
8. The fluid exits the pump through the discharge port, ready to be transferred to the next stage of the process.
9. This cycle repeats continuously with each rotation of the gears, ensuring a consistent flow rate.

Types of Internal Gear Pumps

There are two main types of internal gear pumps, each with unique characteristics and applications:

Involute Gear Pumps

• Crescent Seal: These pumps have a crescent-shaped seal that separates the suction and discharge areas. This design ensures precise control over the flow of fluid, providing a smooth and continuous output.
• Applications: Suitable for handling fluids that require precise control, such as viscous liquids in the food and chemical industries.

Cycloidal Gear Pumps

• Meshing Design: Cycloidal gear pumps do not require a crescent seal. The gears mesh directly, touching at one point, which makes them ideal for applications that require high precision and steady flow.
• Applications: Commonly used in applications requiring a steady and consistent flow, such as hydraulic systems in automotive and manufacturing.

Advantages and Limitations

Advantages

• Efficient for Thick Liquids: Internal gear pumps excel at handling thick and viscous fluids, which are often difficult for centrifugal pumps to manage. This makes them vital in industries such as chemicals, food processing, and manufacturing.
• Self-Priming: These pumps can start pumping immediately because they are self-priming. This eliminates the need for priming during startup, saving time and reducing operational costs.
• Smooth Flow: The positive displacement mechanism ensures a steady and continuous flow rate, making internal gear pumps ideal for precise applications like beverage processing and pharmaceuticals.
• Low Noise: The internal design of gear pumps results in lower noise levels compared to some other types of pumps, making them suitable for applications where noise control is a priority.

Limitations and Solutions

• Flow Slip: Over time, the clearance between the gears and casing can increase, leading to fluid leakage (flow slip). This reduces the pump's efficiency. Shanghai Trustech Technology provides hydraulic gap designs to maintain efficiency and extend the pump's lifespan.
• Susceptibility to Solids: Internal gear pumps can be sensitive to large particulates, as these can cause damage to the gears. Implementing a filter system at the inlet can prevent solid contaminants from entering the pump, ensuring long-term operational reliability.

Applications Across Industries

Internal gear pumps find extensive use across various industries, each with its specific requirements and challenges.

Chemical and Petroleum Industry

• Molten Sulfur: In the chemical industry, internal gear pumps handle materials such as molten sulfur, which requires robust and reliable equipment capable of withstanding high temperatures and corrosive conditions.
• Lubricants and Solvents: These pumps are also essential for moving solvents, lubricants, and other chemicals that demand precise handling and control.

Food and Beverage Industry

• Chocolate and Syrups: Internal gear pumps are ideal for the food industry due to their ability to handle viscous liquids like chocolate and syrup. The pump's smooth operation and tolerance for high viscosity fluids make it a preferred choice for food processing applications.
• Edible Oils: For pumping edible oils and other thick liquids, internal gear pumps offer the precision and reliability needed to maintain product quality.

Automotive and Manufacturing

• Hydraulic Systems: In the automotive industry, internal gear pumps are crucial for hydraulic systems and lubrication processes. These pumps provide the necessary fluid flow for precise and continuous control.
• Fuel Transfer: They are also used in fuel transfer applications, ensuring consistent and reliable performance in various engine systems.

Conclusion

Internal gear pumps are sophisticated and efficient machines that play a critical role in many industrial processes. Understanding their construction and operational principles is crucial for ensuring proper maintenance and management.
At Shanghai Trustech Technology, we are committed to providing high-quality internal gear pumps designed to meet the exact needs of our customers. Our customization services, combined with our expertise in materials and design, enable us to offer reliable solutions for diverse applications.

Whether you need a pump for handling molten sulfur, transferring chocolate in a processing facility, or ensuring smooth operation in a hydraulic system, Shanghai Trustech Technology's internal gear pumps are the perfect choice. Trust our expertise to deliver robust, efficient, and reliable solutions that meet the highest standards.