The external gear pump technology is a type of positive displacement pump. External gear pumps simply use the actions of gears to transfer different types of fluids. In this article, we will illustrate the main features of external and internal gear pumps, the way they work, and other technical information. Finally, we will briefly introduce the external gear pumps produced
by Fluid-o-Tech.
Here is a brief summary of the contents:
• Main features of external gear pumps and internal gear pumps
• How does an external gear pump work
• Design of gears and materials
• External Gear pumps applications
• Advantages and disadvantages of external gear pumps
• The external gear pumps by Fluid-o-Tech
• Technical Specifications & Performance Data of our external gear pumps
• How to Select the Right External Gear Pump for Your Application
There are two basic designs of gear pumps: external and internal.
• an external gear pump utilizes two identical gears meshed side by side, where one gear (driving) is driven by a motor, and it – in turn – drives the other one, the idle (driven) gear. Each gear is supported by a shaft with bearings on both sides of the gear. Fluid trapped between the gear teeth is transported from the inlet to outlet ports, with the gear mesh acting as a seal between the ports.
• an internal gear pump utilizes two meshing gears with the outer (ring) gear typically driving the inner (idler) gear. Fluids trapped between the gears are transmitted from the inlet to the outlet port due to the rotation of the meshing gears, with the gear mesh typically acting as a seal between the ports. An internal gear pump will often use a crescent component to assist in the internal sealing of the gears.
Read also: Micro Gear Pump
In the external gear pumps the two gears mesh with each other in a close fitting housing. As the gears rotate, fluid fills the space between corresponding gear teeth and is carried from the inlet side to the outlet around the external circumference of the gears. Where the teeth mesh together, fluid cannot pass and so it is ejected through the outlet.
External gear pump design might use three different types of gears:
• External spur gears: spur gears utilize straight gear teeth, with the teeth parallel to the axis of rotation.
• External helical gears: helical gears utilize “angled” gears, that is each gear tooth has an identical helix angle (referenced to the axis of rotation) such that the contact ratio of the gear mesh is always greater than 1. A higher contact ratio is beneficial in that two gears are often sharing the load during operation. Typically the helix angle for a pump gear is less than 5 degrees to maintain good hydraulic efficiency.
• External herringbone gears: a gearwheel having two sets of helical teeth, one set inclined at an acute angle to the other so that V-shaped teeth are formed.
External gear pumps can be constructed in a wide variety of materials, such as cast iron, stainless steel, technopolymer, and many others.
External gear pumps are extensively used in various industries where accurate dosing and control are essential. Here's a deeper look into their applications across different sectors:
• Automotive - in the automotive sector, external gear pumps play a crucial role in systems such as in lubrication systems of engines and gearboxes. They are also used for cooling systems and in the precise dosing of fuel and additives
• Food Service - the food service industry relies on external gear pumps for accurate dosing and handling of ingredients, especially in processes involving viscous fluids like oils and syrups. They are essential in applications requiring hygiene and precision, such as in beverage dispensing systems and food packaging processes.
• Health Tech - these pumps are vital also for their precision in dosing and transferring critical fluids. They are widely used in medical devices, such as dialysis machines, infusion pumps, and in laboratory equipment where precise measurement and control of fluids are paramount
• Paints and Inks - external gear pumps are ideal for the paints and inks industry due to their ability to handle viscous materials with high precision. They are used in color mixing systems, inkjet printing, and in the manufacturing processes of paints and coatings, where consistent and accurate dosing is required
• Lubrification and recirculation - these pumps are ideal for lubrication applications in industrial machinery and equipment, ensuring the smooth and efficient operation of moving parts. Additionally, they are used in recirculation systems, such as in heating and cooling applications, where their precise control ensures effective temperature regulation
• Disinfection and metering - in applications requiring disinfection, external gear pumps facilitate the accurate dosing of chemicals and cleaning agents. They are also widely used in water treatment plants and in chemical processing industries for metering applications, where their ability to handle a range of chemicals and fluids at precise rates is crucial.
Thanks to their versatility, resistance, and technical features, external gear pumps offer advantages that are renowned in all their application fields.
Specifically, the advantages we are referring to are:
• extremely stable fluid stream with low pressure pulsations
• high functioning accuracy
• reversibility, which is an advantage because it means that external gear pumps are bidirectional
• suitability to pumping hazardous or hygienic fluids
• excellent suction capability, to avoid air pockets hindering the functioning of external gear pumps
• resistance and long lasting performance
• excellent sealing even in complex applications
• compatibility with great temperature variations, thus they can work with high and low temperatures
• compact size and design that is suitable for different engines
• advantageous quality-price ratio compared to other external gear pumps on the market
Even if their versatility is high, external gear pumps might not be ideal in specific situations.
Specifically, their disadvantages concern:
• run dry processes – which means without using a fluid – for prolonged periods, because these gears are not suitable
• the handling of abrasive fluids having four bearings in the pumped medium and tight tolerances
• the pumping of liquids with suspended solids, because external gear pumps are not compatible with these fluids
Fluid-o-Tech is a market leader in the design and production of external gear pumps and internal gear pumps. At the core of our work, we have chosen to build long-lasting relationships of trust with our Customers, becoming their technology partner for the newest developments.
Fluid-o-Tech external gear pump technology has proven to be the most reliable, efficient, and robust pump technology over the years for use within different applications and industries. Among our product types that are worth mentioning, you should consider:
• magnet drive external gear pumps
• magnet drive external gear pumps
If you have a new project and you are considering this technology, Fluid-o-Tech is the ideal partner. We have experience in developing custom solutions that meet your specific needs.
The MG200–400 series is designed for precise, leak-free fluid management in demanding applications, offering stable flow, excellent chemical compatibility, and fully sealed magnetic drive.
The MG300 series provides enhanced delivery accuracy and temperature stability, making it ideal for applications requiring highly repeatable dosing and smooth, pulsation-free operation.
The PG300 series combines chemical resistance and mechanical robustness thanks to its PPS construction, delivering reliable performance with aggressive fluids.
The MK series is engineered with larger ports and internal passages to optimize flow of viscous fluids, ensuring smooth transfer without cavitation or flow restrictions.
The MGCF AC-driven units offer robust continuous-duty performance, combining magnetic drive pumps with reliable 220V AC motors for consistent flow and pressure control.
The MGCF DC-driven units provide flexible speed control and efficient intermittent-duty operation, combining magnetic drive pumps with versatile 12/24V DC brush motors.
The MKCS series pairs MK gear pumps with high-quality brush DC drives, capable of handling viscous-fluid thanks to larger ports and passages.
The FG100 series integrates a magnetic gear pump with a rotor-less brushless motor, creating an ultra-compact, energy-efficient pump-motor unit for advanced OEM applications.
The Fluid-o-Tech FG200-300-400 series is a compact, integrated pump-motor unit made of AISI 316L stainless steel and chemically resistant materials. It operates quietly and without pulsation, handling liquids up to 95°C, with pressures up to 12 bar and flow rates up to 210 l/h. Its rotor-less motor and electromagnetic drive ensure high reliability, leak-free performance, and energy efficiency. Built-in electronics enable external control, making it ideal for complex systems. NSF-certified versions for potable and food-grade applications are also available.
The DGD series offers a compact direct-drive solution for clean and moderately viscous fluids, providing reliable performance in cost-sensitive or space-constrained installations.
The DGD RS series extends the capabilities of the DGD platform with higher pressure and flow, using stainless steel and Peek components for superior hygiene and durability in food-grade applications.
The DGM series combines magnet drive with compact DC motors, providing a seal-less, maintenance-reduced solution for clean fluids and medium-temperature operating environments.
This section provides a complete technical overview of the Fluid-o-Tech external gear pumps portfolio, including flow ranges, pressure capabilities, materials, temperature limits, and drive options.
All performance values are shown using international (metric) and US customary (imperial) units to ensure full compatibility with global engineering requirements and to support search queries from US-based OEMs and technical buyers.
• 4 mm: 0,3 ml/rev
• 9 mm: 0,6 ml/rev
• 13 mm: 0,9 ml/rev
• 17 mm: 1,2 ml/rev
Selecting the most suitable external gear pump requires evaluating a combination of fluid characteristics, operating conditions, installation constraints, and performance requirements.
External gear pumps are highly versatile and reliable, but their efficiency and lifetime depend on a correct match between pump design and application parameters.
Below is a structured guide to help engineers and OEM designers choose the proper Fluid-o-Tech external gear pump.
Viscosity directly affects flow stability, volumetric efficiency, internal leakage, and required driving torque.
• Low-viscosity fluids (<10 cP): select tighter tolerances, harder materials (e.g., PEEK™), and higher speed capability
• Medium viscosity (10–200 cP): suitable for most MG / MG300 / PG / FG series
• High viscosity (>200 cP): prefer MK series with enlarged internal passageways to avoid friction and cavitation
• Extremely viscous or shear-sensitive fluids: reduce speed and consider magnet drive if chemical compatibility is required
Temperature influences material expansion, clearances, magnetic coupling torque, and seal performance.
• High-temperature applications (up to 120°C / 248°F): MG, MG300, MK series
• Medium temperatures (<95°C / 203°F): FG and DGM series
• Very low viscosity at high temperature: ensure stable magnet coupling and adjust speed accordingly
Ensure that housing, gears, bushings, magnets, and seals match the fluid chemistry.
• AISI 316L stainless steel: excellent corrosion resistance
• Gears/bushings: PEEK™ for mechanical strength, PTFE™ for chemical compatibility
• Elastomers: EPDM for water and detergents, Viton for oils and solvents, PTFE™ for aggressive chemicals
• For aggressive or unknown fluids, always request a compatibility assessment.
• Differential pressure defines required torque and energy consumption
• Static pressure (system pressure) determines mechanical stress and sealing performance
• Higher pressure applications (>10 bar) benefit from reduced clearances and stronger magnet coupling
• Gear pumps produce flow proportional to speed → set speed based on required precision and noise level
• For dosing applications, low pulsation models (MG / MG300 / FG) ensure best repeatability
• Internal leakage increases when:
• Viscosity decreases
• Temperature increases
• Clearances are too large for the application
• Pressure rises sharply
Choosing the right gear and bushing material reduces volumetric losses significantly.
• Keep suction lines short and wide
• Avoid sharp bends and restrictions
• Maintain proper inlet pressure to avoid vapor formation
• For viscous fluids, reduce speed to avoid cavitation
• Avoid prolonged dry-running
• For poor-lubricity fluids (e.g., water, solvents), use appropriate materials (PEEK™, PTFE™)
• When lubrication is critical, select magnet-drive versions to avoid leakage risks
• Magnet drive pumps: best for chemical compatibility, zero leakage, and safety
• Direct drive pumps: ideal for compact installations and cost-sensitive applications
• Brushless DC versions (FG, DGD PRO): allow speed control and integration into advanced devices
• Choose materials based on expected wear (PEEK™ for long life, PTFE™ for aggressive fluids)
• Install proper filtration upstream if the fluid may contain particles
• Check seals periodically when using elastomeric materials
• Magnet drives minimize maintenance by eliminating dynamic seals
• Install the pump as close as possible to the fluid source
• Ensure proper alignment if using direct drive shafts
• Minimize vibration transfer from the motor
• Avoid air pockets to guarantee priming and accurate dosing
• Use flexible tubing or couplings to reduce stress on the pump housing
• Consider thermal expansion when installing pumps that operate above 80–100°C
• Viscosity (cP or mm²/s)
• Temperature range
• Chemical compatibility (housing, gears, bushings, seals)
• Lubricity of the fluid
• Presence of particulates (should be avoided)
• Required flow rate (l/h or GPH)
• Required differential pressure (bar / psi)
• System static pressure
• Required dosing accuracy or repeatability
• Maximum allowable pulsation
• Maximum available motor torque
• Preferred drive type (magnet, direct, DC, brushless)
• Maximum temperature at pump location
• Noise requirements
• Space constraints and mounting orientation
• Suction conditions (NPSH margin)
• Filtration requirements
• Accessibility for maintenance
• Environmental exposure (corrosion, humidity, chemicals)
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