Internal Gear Pumps: Efficiency for Industrial Applications

In industrial applications, efficient and reliable fluid transfer is crucial. Gear pumps, a positive displacement pump, are essential for this purpose. These pumps are known for their simplicity, durability, and ability to handle various fluids, making them vital in many industries. Among gear pumps, the internal gear pump stands out for its versatility and superior performance. This blog explores internal gear pumps’ features, applications, and benefits.

Internal gear pumps have an innovative design that offers exceptional efficiency and operational flexibility. Unlike an external gear pump, which uses two identical gears mounted off-centre, internal gear pumps have two gears of different sizes that engage internally. This design minimizes pulsation and allows for accurate flow control when handling high-viscosity liquids and a wide range of temperatures. Internal gear hydraulic pumps can maintain a steady flow regardless of pressure variations, emphasizing their importance in modern industrial applications.

This blog provides a comprehensive understanding of, and discusses how to best make an internal gear pump work. We will examine the basic principles and operation of gear pumps and then delve into the specifics of internal gear pumps. Key topics include their construction, working mechanism (including rotational speed), and the advantages they offer over other types of pumps. We will also explore the industrial applications of internal gear hydraulic pumps in sectors like chemical processing, food and beverage, and automotive manufacturing and how they effectively pump fluids. Finally, we will discuss the latest advancements and trends in internal gear pump technology.

Join us as we uncover the reasons behind internal gear pumps’ popularity and their crucial role in improving industrial efficiency.

What is an Internal Gear Pump?

Detailed Definition and Working Principle

An internal gear pump is a positive displacement pump that uses two gears of different sizes to move fluid. The pump consists of an inner rotor, also known as the driving gear, and an outer rotor, the larger gear with internal teeth. The inner rotor is offset within the outer rotor, and as they rotate, the gears create expanding and contracting cavities that move the fluid from the inlet to the outlet. The idler gear, a smaller gear nested inside the rotor gear, creates a low-pressure zone and draws liquid into the pump.

The working principle of an internal gear pump is based on the following steps:

Inlet Phase: As the inner rotor turns, its rotating gears mesh with the outer rotor’s, creating a void that draws fluid into the pump through the pump inlet.

Transfer Phase: The fluid is carried between the gear teeth of the inner and outer rotors as they continue to rotate. The expanding volume created by the separation of the gears pulls the fluid along as the gear teeth engage.

Outlet Phase: The teeth meshing on the discharge side reduces the volume between the gears, forcing the fluid out through the outlet. The rotor gear creates a liquid seal with the pump casing, ensuring efficient fluid transfer.

This process allows internal gear pumps to handle a wide range of viscosities and deliver a smooth, pulsation-free flow, which is especially beneficial for precise fluid transfer in various industrial applications. An internal gear pump operates using these components to create suction at the pump inlet, transfer fluid around the pump casing, and expel it at the discharge outlet.

Comparison with Other Types of Gear Pumps

Internal gear pumps differ from external gear pumps and other types of positive displacement pumps in several ways:

Internal Gear Pumps vs. External Gear Pumps:

Design: Internal gear pumps use two differently sized gears (one inside the other), while external gear pumps use two identical gears that rotate against each other.

Fluid Handling: Internal gear pumps are better suited for handling high-viscosity fluids and provide a smoother flow with less pulsation than external gear pumps.

Applications: Internal gear pumps are commonly used in applications requiring precise fluid control and the ability to handle various fluid viscosities, such as in chemical processing, food and beverage, and lubrication systems.

Efficiency: Internal gear pumps can experience ‘flow slip’ over time due to increased clearances, which can initially have a small effect on efficiency but worsen until a critical point is reached.

Internal Gear Pumps vs. Lobe Pumps:

Design: Lobe pumps use two rotors with lobes that rotate without touching, whereas internal gear pumps have intermeshing gears.

Efficiency: Internal gear pumps generally offer higher volumetric efficiency and better handling of high-viscosity fluids than lobe pumps.

Pulsation: Internal gear pumps provide smoother and less pulsating flow than lobe pumps, making them ideal for applications requiring precise flow control.

Mechanism: Internal gear pumps work using a positive displacement mechanism, where rotating interlocking gears handle high-viscosity fluids through filling, transfer, and delivery stages.

Historical Development and Technological Advancements

The concept of gear pumps dates back to ancient times, but the development of internal gear pumps began in the early 20th century. Jens Nielsen, who patented the design in 1910, is credited with inventing the internal gear pump. This innovation addressed the limitations of external gear pumps by providing a more efficient and versatile pumping solution.

Over the years, internal gear pumps have undergone significant technological advancements to enhance their performance and reliability. Key developments include:

Material Improvements: Advanced materials such as stainless steel, cast iron, and specialized alloys have increased the durability and corrosion resistance of internal gear pumps, making them suitable for a broader range of industrial applications.

Seal Technologies: Advancements in seal designs, including mechanical seals and magnetic couplings, have improved the leakage prevention and overall efficiency of internal gear hydraulic pumps.

Precision Manufacturing: Modern manufacturing techniques, such as computer numerical control (CNC) machining, have enabled the production of internal gear pumps with tighter tolerances and improved performance characteristics.

Variable Speed Drives: Integrating variable frequency drives (VFDs) with internal gear pumps has allowed for precise control of pump speed and flow rate, enhancing their adaptability to different process requirements.

DAE piston pump

Critical Components of Internal Gear Pumps

Description of the Main Components: Gears, Casing, and Shafts


The internal gear pump comprises two gears: the inner (driven) rotor and the outer (driven) rotor. The inner rotor has smaller external teeth, while the outer rotor has more prominent internal teeth.

The gears are designed to mesh internally, creating a chamber for fluid transfer. As the inner rotor rotates, it drives the outer rotor, causing the gears to engage and disengage, creating cavities that move the fluid from the inlet to the outlet.


An internal gear pump casing is a robust housing that encloses the gears and maintains the alignment and spacing necessary for efficient operation.

It provides structural support and ensures the fluid is contained and directed through the pump. The casing also helps minimize leaks and withstand pressure pumping various fluids. The fixed, crescent-shaped partition within the casing seals the liquid between the inlet and outlet ports, facilitating efficient fluid transfer.


The shafts in an internal gear pump connect the gears to the drive mechanism, which could be an electric motor or another power source.

The driving shaft rotates the inner rotor, while the driven shaft may be integral to the outer rotor or supported by bearings within the casing. The precise alignment of these shafts is critical for the smooth operation of the pump.

Material Considerations for Different Industrial Applications

Internal gear pumps are used in a wide range of industrial applications, each with specific material requirements to handle various fluids and operating conditions:

Stainless Steel:

Stainless steel is commonly used in internal gear pumps for corrosive fluids applications, such as chemical processing, pharmaceuticals, and food and beverage industries.

Its corrosion resistance, durability, and ease of cleaning make it ideal for maintaining the pumped fluid’s integrity and the pump’s longevity.

Cast Iron:

Cast iron is often used for internal gear pumps in general industrial applications where the fluids are less corrosive but may contain abrasive particles.

Its robustness and wear resistance make it suitable for handling oils, fuels, and other lubricating fluids in automotive and machinery applications.

Specialized Alloys and Coatings:

For extreme conditions, such as high temperatures or highly abrasive fluids, specialized alloys (e.g., Hastelloy, Inconel) or coatings (e.g., ceramic, PTFE) are employed.

These materials enhance performance and durability, ensuring reliable operation in demanding environments such as mining, power generation, and the petrochemical industries.

Importance of Precision Engineering in the Performance of Internal Gear Pumps

Precision engineering is paramount in the design and manufacture of internal gear pumps due to several critical factors:

Tight Tolerances:

The performance of internal gear pumps heavily relies on the precise fit and alignment of the gears, shafts, and casing. Tight tolerances ensure minimal internal leakage, optimal efficiency, and consistent flow rates.

Precision machining of these components prevents excessive wear, noise, and vibration, which can compromise the pump’s longevity and reliability.

Efficiency and Flow Control:

Precision engineering allows accurate control of the clearances between the gears and casing, directly affecting the pump’s volumetric efficiency.

Maintaining these clearances ensures that the internal gear hydraulic pump can deliver a smooth, pulsation-free flow, essential for applications requiring precise fluid handling.

Durability and Reliability:

High-quality materials and precision manufacturing techniques enhance the durability and reliability of internal gear pumps.

Precision-engineered pumps are less prone to failure, reducing downtime and maintenance costs. This reliability is crucial in critical industrial processes where pump failure can lead to significant production losses.


Advantages of Internal Gear Pumps

Efficiency and Energy-Saving Features

Internal gear pumps are renowned for their high efficiency and energy-saving capabilities. Their design ensures minimal fluid slippage and optimal volumetric efficiency, translating to more fluid pumped per rotation than other pump types. This efficiency reduces the energy required to achieve the desired flow rate, making internal gear pumps more cost-effective in the long run.

One primary reason for this efficiency is the close tolerances between the gears and the casing. These tight clearances minimize internal leakage, ensuring that most of the energy input is used to move the fluid rather than overcome friction or compensate for losses. Additionally, internal gear hydraulic pumps can operate efficiently across various speeds, making them adaptable to multiple process requirements without significant energy penalties.

Capability to Handle a Wide Range of Viscosities

Internal gear pumps are versatile and can handle fluids with various viscosities, from thin solvents to thick oils and even semi-solids. This capability makes them suitable for numerous industrial applications in the chemical, food and beverage, and lubrication industries.

The design of internal gear pumps allows them to maintain consistent performance regardless of the fluid’s viscosity. The positive displacement mechanism ensures a constant flow rate, while the internal meshing of the gears provides the necessary force to move even highly viscous fluids. This adaptability is particularly beneficial in applications where fluid properties vary significantly, ensuring reliable operation under all conditions.

Smooth and Low-Pulsation Flow Characteristics

One of the standout features of internal gear pumps is their ability to deliver a smooth and low-pulsation flow. The internal meshing of the gears creates a continuous and even fluid transfer, which reduces pulsations and vibrations. This characteristic is crucial in applications requiring precise flow control and minimal fluid disturbance, such as metering, dosing, and hydraulic systems.

The smooth flow of internal gear pumps improves process control and reduces the mechanical stress on the pump and associated piping. This reduction in stress leads to longer equipment life and decreased maintenance requirements, further enhancing the pump’s reliability and cost-effectiveness.

Reliability and Longevity in Various Operational Environments

Internal gear pumps are built to be highly reliable and durable, operating efficiently in diverse and demanding environments. Their robust construction and high-quality materials can withstand harsh conditions, including high pressures, extreme temperatures, and abrasive or corrosive fluids.

Several factors contribute to the reliability and longevity of internal gear hydraulic pumps:

  • Material Selection: Materials such as stainless steel, cast iron, and specialized alloys resist wear, corrosion, and chemical attack.

  • Precision Engineering: The precise manufacturing of components ensures tight tolerances, reducing wear and maintaining optimal performance over time.

  • Advanced Sealing Technologies: Modern seals prevent leaks and contamination, ensuring the pump remains efficient and reliable throughout its service life.

Combining these factors means that internal gear pumps can deliver consistent and dependable performance over extended periods, even in the most challenging industrial environments. This reliability reduces downtime and maintenance costs, making internal gear pumps a preferred choice for critical applications.

Applications in Various Industries

Chemical Processing: Handling of Corrosive and Viscous Fluids

Internal gear pumps are widely used in chemical processing because they handle both corrosive and highly viscous fluids. The materials used in these pumps, such as stainless steel and specialized alloys, provide excellent resistance to chemical attack, ensuring long-term durability and reliability. Their efficient design minimizes fluid slippage and internal leakage, making them ideal for transferring aggressive chemicals and maintaining process integrity.

Food and Beverage: Sanitary Design Options for Food-Grade Applications

In the food and beverage industry, internal gear pumps are favored for their sanitary design options, which ensure compliance with strict hygiene standards. These pumps can be made from food-grade materials and feature easy-to-clean designs to prevent contamination. Their ability to handle various viscosities makes them suitable for transferring multiple food products, from thin liquids to thick pastes, while maintaining a smooth, low-pulsation flow that preserves product quality.

Petrochemical: Pumping of Crude Oil, Lubricants, and Other Petroleum Products

Internal gear pumps are crucial in the petrochemical industry, where they pump crude oil, lubricants, and other petroleum products. Their robust construction and ability to handle high-viscosity fluids make them ideal for these demanding applications. These pumps are also used for handling materials like tar polyurethane foam, asphalt, and bitumen. The pumps’ efficiency and reliability ensure consistent performance in the transfer and processing of petroleum products, contributing to the overall efficiency of petrochemical operations.

Pharmaceutical: Precision Dosing and Handling of Sensitive Substances

In the pharmaceutical industry, precision and reliability are paramount. Internal gear pumps excel in these environments because they provide accurate dosing and gentle handling of sensitive substances. Their smooth, pulsation-free flow ensures that delicate pharmaceutical products are transferred without degradation or contamination. Additionally, using high-quality, inert materials prevents chemical reactions with the pumped substances, ensuring product purity.

Automotive: Role in Lubrication Systems and Hydraulic Applications

Internal gear pumps are integral to the automotive industry, particularly in lubrication systems and hydraulic applications. Their efficient design ensures consistent delivery of lubricants to engine components, reducing wear and extending the life of the machinery. In hydraulic systems, internal gear hydraulic pumps provide the necessary pressure and flow for various functions, from power steering to braking systems, enhancing vehicle performance and safety.


Internal Gear Hydraulic Pumps

Specific Focus on Hydraulic Applications

Internal gear hydraulic pumps are designed to excel in hydraulic applications where precise control and high-pressure capabilities are crucial. These pumps are integral components of hydraulic systems, efficiently converting mechanical power into hydraulic energy. Their design ensures consistent fluid flow, making them ideal for accurate and reliable fluid power applications.

Benefits in Hydraulic Systems: Precise Control and High-Pressure Capabilities

Precise Control:

Internal gear hydraulic pumps provide smooth and precise fluid flow, essential for maintaining the accurate operation of hydraulic systems. This precision enables fine control of hydraulic actuators, ensuring that machinery and equipment perform tasks accurately.

The minimal pulsation and steady flow characteristics of internal gear pumps contribute to the stability and responsiveness of hydraulic systems, enhancing overall performance.

High-Pressure Capabilities:

These pumps can handle high pressures, making them suitable for demanding hydraulic applications. Their robust construction and design allow them to operate efficiently under high-pressure conditions, delivering the necessary force for various hydraulic tasks. The same pump can be used for multiple hydraulic applications, highlighting its versatility.

The ability to maintain performance at high pressures ensures that internal gear hydraulic pumps can meet the rigorous demands of industrial and mobile hydraulic systems.

Examples of Use in Mobile and Industrial Hydraulic Equipment

Mobile Hydraulic Equipment:

Construction Machinery: Internal gear hydraulic pumps power hydraulic systems in construction equipment like excavators, bulldozers, and loaders, lifting, digging, and moving heavy loads.

Agricultural Machinery: In tractors and harvesters, these pumps provide the hydraulic power needed for various attachments and implements, facilitating efficient farming operations.

Transport Vehicles: Internal gear pumps are found in hydraulic systems of trucks and other transport vehicles, assisting in functions such as lifting, tipping, and steering.

Industrial Hydraulic Equipment:

Manufacturing Machinery: In industrial settings, internal gear hydraulic pumps are used in machinery for pressing, molding, and cutting operations, where precise control and high pressure are necessary for optimal performance.

Material Handling Equipment: Equipment such as forklifts and conveyors rely on these pumps for smooth and reliable hydraulic power, ensuring efficient material handling and movement.

Hydraulic Presses: Internal gear pumps are used in hydraulic presses for applications like metal forming, where high-pressure capabilities and precise control are critical for producing accurate and consistent results.

Internal gear hydraulic pumps are vital for mobile and industrial hydraulic equipment. Their precise control and high-pressure capabilities make them indispensable for reliable and efficient hydraulic power applications. Whether in construction, agriculture, manufacturing, or material handling, internal gear pumps deliver the performance and reliability needed to drive various hydraulic systems.

Selection Criteria for Internal Gear Pumps

Factors to Consider: Fluid Type, Viscosity, Temperature, and Pressure Requirements

Fluid Type: The chemical composition and properties of the pumped fluid are critical in selecting the right internal gear pump. Some fluids may be corrosive, abrasive, or reactive, necessitating specific materials and designs to ensure compatibility and longevity of the pump components.

Viscosity: Internal gear pumps are well-suited for handling various viscosities, from thin solvents to thick oils and semi-solids. The pump’s design must be chosen based on the fluid viscosity to ensure efficient operation without causing excessive wear or energy consumption.

Temperature: The fluid’s operating temperature affects the selection of materials and seals in the internal gear pump. High temperatures may require heat-resistant materials and unique sealing solutions to maintain pump integrity and performance.

Pressure Requirements: Understanding the system’s pressure requirements is essential for selecting an internal gear pump that can handle the maximum and continuous operating pressures without compromising efficiency or safety. The pump must deliver consistent performance under the specified pressure conditions.

Importance of Matching Pump Specifications to Application Needs

Matching the pump specifications to the application’s needs is crucial for ensuring optimal performance, efficiency, and reliability. An improperly selected pump can lead to issues such as insufficient flow rates, excessive wear, energy inefficiency, and potential system failures. Key considerations include:

  • Flow Rate: Ensure the pump can provide the required flow rate for the application without overworking or underperforming.

  • Compatibility: Select materials and designs compatible with the fluid type and operating environment to prevent corrosion, wear, and chemical reactions.

  • Operational Efficiency: Choose a pump that operates efficiently at the desired viscosity, temperature, and pressure ranges to minimize energy consumption and operational costs.

  • Longevity: Opt for pumps with features that enhance durability and reduce maintenance needs. This will extend the pump’s operational life and reduce downtime.

Customization Options Available from Manufacturers Like DAE Pumps

Manufacturers like DAE Pumps offer a range of customization options to meet specific application requirements. These customizations can include:

  • Material Selection: Options for different materials, such as stainless steel, cast iron, and specialized alloys, to match the fluid’s chemical properties and abrasiveness.

  • Seal Types: Various sealing solutions, including mechanical seals and magnetic couplings, to handle different temperatures and pressure conditions while preventing leaks.

  • Pump Configurations: Custom pump designs tailored to specific installation constraints and operational needs, ensuring a perfect fit for the system.

  • Variable Speed Drives: Integration with variable frequency drives (VFDs) to allow for precise control of pump speed and flow rate, enhancing adaptability to changing process conditions.

  • Special Coatings: Apply protective coatings to improve resistance to corrosion and wear, thereby extending the pump’s service life in harsh environments.



In conclusion, internal gear pumps are a versatile and efficient solution for various industrial applications. We’ve explored their unique features, including their ability to handle multiple viscosities, smooth and low-pulsation flow characteristics, and reliability and longevity in different operational environments. We also discussed the critical components of internal gear pumps, their advantages in hydraulic systems, and the essential factors to consider when selecting the right pump for specific needs.

Selecting the right internal gear pump ensures optimal application performance, efficiency, and reliability. Factors such as fluid type, viscosity, temperature, and pressure requirements must be considered to match the pump specifications to the application’s demands. Customization options available from manufacturers like DAE Pumps can further enhance the pump’s suitability and effectiveness for specific operational needs.

DAE Pumps offers extensive experience and expertise in providing high-quality internal gear hydraulic pumps for those seeking expert advice and tailored solutions. We encourage readers to contact DAE Pumps to discuss their specific requirements and benefit from our comprehensive range of products and customization options. Let us help you find the perfect internal gear pump solution for your industrial applications, ensuring efficiency, reliability, and long-term performance.

Contact DAE Pumps today for expert guidance and the best internal gear pump solutions tailored to your needs.