External Gear Pumps - Precision Pumping Technology for High Pressures and Defined Flow Rates
External gear pumps convey lubricable fluids using a volumetrically defined principle with high repeatability. Two externally toothed gears rotate within a housing with tight tolerances, transporting the fluid in the spaces between the teeth and separating the suction and discharge sides via meshing and clearance geometry.
Harton Anlagentechnik GmbH consistently designs external gear pumps based on the fluid, viscosity, differential pressure, lubricity, and sealing concept. This results in robust solutions for pumping, supply, and metering tasks where pressure stability, reproducible flow rate, and controlled leakage are critical.
Harton Anlagentechnik GmbH consistently designs external gear pumps based on the fluid, viscosity, differential pressure, lubricity, and sealing concept. This results in robust solutions for pumping, supply, and metering tasks where pressure stability, reproducible flow rate, and controlled leakage are critical.
Types, Variants, and Distinctions
Depending on the task at hand, different variants are used:
For standard pumping applications involving oil-containing and lubricating fluids under stable operating conditions.
For applications with high differential pressures, in which the bearings, housing design, and clearance configuration must be rated for high mechanical loads.
For small, precise flow rates with high repeatability and controllable speed.
For applications with increased requirements for emission control, media purity, or leak-free operation.
Technical Specifications:
Technical Specifications:
- Compared to internal gear pumps, external gear pumps are often more compact and capable of withstanding higher pressures.
- Compared to screw pumps, they achieve high pressures with a compact design, but their operation is slightly more pulsating due to their design.
- Compared to other positive-displacement pumps, the lubricity of the fluid is a key design factor.
External gear pumps are ideal wherever a compact design, high pressure, and clean volumetric delivery are required. Our in-house engineers consider not only the target flow rate but also the actual operating point, taking into account slip, temperature, viscosity, and system losses.
What matters in practice:
Especially when dealing with low-viscosity media, high differential pressures, or critical emission requirements, the correct design is crucial for efficiency, service life, and process reliability.
What matters in practice:
- defined flow rate based on the positive displacement principle
- High pressure capacity in a compact design
- Stable supply of lubricating fluids
- Precise control via speed or frequency converters
- Project-specific sealing strategy, ranging from shaft seals to magnetic couplings
Especially when dealing with low-viscosity media, high differential pressures, or critical emission requirements, the correct design is crucial for efficiency, service life, and process reliability.
External gear pumps are typically used in systems where lubricating fluids must be moved at a defined pressure and with a reproducible flow rate.
Typical applications:
Typical industries:
For high-viscosity fluids, we also test suction behavior, startup torque, and temperature control. For low-viscosity fluids, we evaluate volumetric efficiency with particular care, as slip increases as viscosity decreases.
Typical applications:
- Hydraulic systems
- Lubricating oil systems
- Process oil supply
- Fuel delivery
- Metering Applications
- Supplying Units with Oil-Containing Fluids
Typical industries:
- Machinery and Plant Engineering
- Energy and utility engineering
- Test bench technology
- Lubricant and Fuel Technology
- Industrial Dosing and Supply Systems
For high-viscosity fluids, we also test suction behavior, startup torque, and temperature control. For low-viscosity fluids, we evaluate volumetric efficiency with particular care, as slip increases as viscosity decreases.
Our external gear pumps are designed based on actual process data. The following ranges serve as a technical guide:
More Than Just Displacement Volume
It is essential to understand in practice that the actual flow rate does not depend solely on the geometric displacement volume. Internal leakage increases with differential pressure and decreases as viscosity increases. For this reason, our employees always consider the overall interplay of the fluid, gap size, temperature, and pressure level.
| Flow Rate Q | 0.1 to 200 m³/h |
| Differential Pressure Δp | 10 to 200 bar |
| Viscosity | 1 to 25,000 mPa·s |
| Temperature range | -20 °C to +200 °C |
| Particle boundary | typically up to 50 µm |
| Gas content | 0 to 10 vol.% |
| Regulation | FU operation is possible, depending on the application and speed range |
The service life of an external gear pump depends heavily on the material, bearing design, and thermally clean clearance.
Typical housing materials:
Gear materials:
Seal materials:
Typical housing materials:
- Cast steel
- Ductile iron
- Stainless steel, e.g., 1.4404 or 1.4571
Gear materials:
- quenched and tempered steels
- hardened steels with defined surface hardness and roughness
- Bearing arrangement:
- sliding bearings and medium-lubricated
- Rolling bearings
- External lubrication system for critical media or marginal lubrication
Seal materials:
- NBR
- FKM
- EPDM
- FFKM
We select materials based on their suitability for the conveyed medium and on our experience with customers. In addition, we evaluate thermal expansion under cyclic loading to ensure that neither impermissibly large gaps nor critical contact occurs. In cases of boundary lubrication, wear, or corrosion risk, coatings such as DLC, hard chrome, or thermal spray systems may be appropriate.
Challenging media? This is exactly where standard and engineering diverge
Not every fluid is equally suitable for external gear pumps. The key factors are not only chemical resistance but also lubricating performance under actual operating conditions.
Particularly well-suited:
To be evaluated critically:
Solids are generally a concern for external gear pumps, as particles can damage gear flanks and bearing surfaces. Therefore, a suitable filter or fine-filter system is often not just an option, but a requirement.
Particularly well-suited:
- Hydraulic oils
- Lubricating oils
- Heating oils
- Fuels
- Other lubricating process media
To be evaluated critically:
- Low-viscosity media with increased slip
- High-viscosity media with challenging suction characteristics
- Media containing solids
- media that outgas or carry gas
- Chemically aggressive fluids with increased demands on materials and leak tightness
Solids are generally a concern for external gear pumps, as particles can damage gear flanks and bearing surfaces. Therefore, a suitable filter or fine-filter system is often not just an option, but a requirement.
Seals, Safety, and Interfaces
For external gear pumps, the sealing design is a key selection criterion. Depending on the fluid and operating standards, we offer the following configurations:
Additional safety-related points:
- single shaft seal
- double shaft seal
- magnetic coupling for seal-less operation
- For positive displacement pumps, the following also applies: Overpressure protection is absolutely essential. If the discharge side is shut off, the pressure continues to rise. For this reason, safety valves or bypass solutions must be included in the design.
Additional safety-related points:
- Shut-off or flushing systems for high-pressure or high-temperature applications
- DIN or ANSI flanges with a defined pressure rating
- Permissible piping loads
- Grounding and equipotential bonding for flammable media
- Project-specific ATEX assessment based on zone, gas group, and temperature class
Drives, Control, and Energy
The drive is typically provided by an electric motor with a coupling or gearbox. The permissible speed range is not set as a flat rate, but is determined by the medium, viscosity, suction conditions, and bearing load.
Key engineering considerations:
Cold start behavior is often more critical than steady-state operation, especially with high-viscosity fluids. Our engineers therefore take into account both continuous operation and real-world start-up conditions.
Key engineering considerations:
- Frequency converter (FU) operation for stable metering and pressure control
- Minimum speed to ensure adequate lubrication
- Start-up torque for highly viscous media
- Preheating or temperature control concept for cold starts
- Evaluation of power consumption based on load profile and operating hours
Cold start behavior is often more critical than steady-state operation, especially with high-viscosity fluids. Our engineers therefore take into account both continuous operation and real-world start-up conditions.
Integration, Installation, and Peripherals
An external gear pump will only operate stably over the long term if the surrounding environment is properly designed.
Key integration points:
Customer requests are taken into account whenever possible. However, it remains crucial that the peripheral equipment is technically compatible with the fluid and the load conditions.
Key integration points:
- a short and generously sized suction line
- Filter or fine filter appropriate for the particle size limit
- Bypass and check valves
- Pressure and temperature measurement
- Optional flow measurement
- Heating jacket, tracing, or insulation for viscous or solidifying media
- Precise alignment of the pump and drive to reduce stress on bearings and seals
Customer requests are taken into account whenever possible. However, it remains crucial that the peripheral equipment is technically compatible with the fluid and the load conditions.
Monitoring, Maintenance, and Operational Safety
External gear pumps benefit from clearly defined monitoring parameters. This allows deviations to be detected early, before seals, bearings, or gear flanks are damaged.
Useful monitoring parameters:
The maintenance strategy is defined as either scheduled or condition-based. The primary TCO drivers in this context are typically the seal, filter management, the lubricity of the medium, and the quality of the installation environment.
Useful monitoring parameters:
- Pressure to detect blockages, filter clogging, or shut-off conditions
- Temperature at bearings, seals, and the housing
- Current or power consumption as an indication of changes in viscosity or wear
- Vibrations in larger units
- Alarm and shutdown logic in the plant control system
The maintenance strategy is defined as either scheduled or condition-based. The primary TCO drivers in this context are typically the seal, filter management, the lubricity of the medium, and the quality of the installation environment.
Quality, Testing, and Documentation
Before delivery, we define the scope of testing to suit the application. Typical elements include:
In the standard configuration, we provide the project-specific documentation in accordance with the agreed scope. FAT and, optionally, SAT can be defined additionally.
- Functional test
- Pressure and leak testing
- Performance test for Q/Δp
- Material certificates in accordance with EN 10204 2.2 or 3.1, as required
- Data Sheet
- General Arrangement Drawing
- Spare Parts List
- Operating instructions
- CE or ATEX compliance
- Test Reports
In the standard configuration, we provide the project-specific documentation in accordance with the agreed scope. FAT and, optionally, SAT can be defined additionally.
Advantages of Harton External Gear Pumps
- Volumetrically controlled flow
- High pressures in a compact design
- Stable delivery of lubricating fluids
- Reproducible metering operation with a frequency converter
- Customizable material, clearance, and bearing design
- Optionally seal-less via magnetic coupling
- Technical design based on medium, pressure, and operating standard
Types and Variants of Our External Gear Pumps
We develop and manufacture external gear pumps for a wide variety of pumping tasks and process requirements. Whether you need a standard model, a heatable, magnetically coupled, chemical-resistant, high-pressure, or precision metering gear pump—we offer the right solution for your fluid and your application. We customize each pump to your specific technical requirements as needed and support you every step of the way, from design through commissioning.
Media that solidify when cooled require intelligent thermal management. Our technicians integrate heating jackets for steam or thermal oil directly into the pump body. Our many years of experience show that uniform heating of the pump is crucial for the service life of the seals. Therefore, our project engineers develop control concepts that only authorize operation once the exact melting temperature has been reached.
| Gas content | ＜ 3 % |
| NPSH | 3 - 6 m |
| Seal | Packing / HT Mechanical Seal |
| Volume flow rate Q | 5 - 1.500 l/min |
| Materials | Cast steel, HT stainless steel |
| Pressure | up to 40 bar |
| ATEX | Yes |
| Efficiency | 75 - 85 % |
| Performance | 2 - 75 kW |
| Rotational speed | 100 - 1.500 min⁻¹ |
| Temperature | up to +450 °C |
| Viscosity | up to 200,000 mPas |
| Solids | minimal |
For highly corrosive media, our project engineers develop customized plant designs based on 1.4404 stainless steel or special alloys. Our second-generation expertise enables us to precisely account for thermal expansion coefficients in the design. This prevents the gears from seizing up under fluctuating temperatures and ensures long-term process stability. Our technicians validate each sealing unit to ensure compliance with strict environmental regulations.
| Solids | minimal (＜ 20 µm) |
| Gas content | ＜ 2 % |
| NPSH | Optimized for low inflows |
| Seal | Double GLRD / Magnetic Coupling |
| Volume flow rate Q | 0,1 - 600 l/min |
| Materials | 1.4404, Hastelloy, Titanium |
| Pressure | up to 40 bar |
| ATEX | Ja |
| Efficiency | 70 - 85 % |
| Performance | 0,25 - 45 kW |
| Rotational speed | 200 - 1.800 min⁻¹ |
| Temperature | -50 °C to +300 °C |
| Viscosity | 0,5 - 500.000 mPas |
In polymer processing, extreme pressures are the norm. Our project engineers design reinforced housing configurations made of hardened tool steels for these applications. Thanks to over 40 years of experience in machine and plant engineering, our technicians know exactly how to stabilize the lubrication of the plain bearings using the process medium itself, thereby minimizing wear at pressures up to 350 bar.
| Efficiency | ＞ 90 % |
| Performance | up to 250 kW |
| Rotational speed | 10 - 500 min⁻¹ |
| Temperature | up to +350 °C |
| Viscosity | up to 10,000,000 mPas |
| Solids | none |
| Gas content | 0 % |
| NPSH | High inlet pressure required |
| Seal | Return thread / cooled |
| Volume flow rate Q | 0,5 - 1.000 l/min |
| Materials | Tool steel, hardened |
| Pressure | up to 350 bar |
| ATEX | Yes |
Wherever toxic or environmentally hazardous substances are transported, our specialists rely on hermetically sealed magnetic couplings. Our engineers use state-of-the-art engineering expertise to cool eddy current losses in the stator shell through optimized partial current routing. For our customers, this means a maintenance-free solution with no risk of leakage at the shaft passage, which safely expands the operating limits of your plant.
| Temperature | -100 °C to +250 °C |
| Viscosity | up to 10,000 mPas |
| Solids | completely free of solids |
| Gas content | 0 % |
| NPSH | critical (vapor pressure test) |
| Seal | Magnetic coupling |
| Volume flow rate Q | 0,05 - 300 l/min |
| Materials | Stainless steel, ceramic bearings |
| Pressure | up to 100 bar |
| ATEX | Yes |
| Efficiency | 65 - 80 % |
| Performance | up to 30 kW |
| Rotational speed | up to 3,000 min⁻¹ |
When every drop counts, our customers rely on the dosing expertise of Harton Anlagentechnik GmbH. Our specialists manufacture these pumps with extremely tight tolerances to ensure virtually pulsation-free flow. Our engineers support you with system integration into automated production lines so that your validation processes deliver reproducible results at all times.
| Volume flow rate Q | 0,01 - 20 l/min |
| Materials | Stainless steel, ceramic, DLC |
| Pressure | up to 80 bar |
| ATEX | Zone 1 |
| Efficiency | ＞ 95 % |
| Performance | 0,1 - 3 kW |
| Rotational speed | 10 - 200 min⁻¹ |
| Temperature | -20 °C bis +150 °C |
| Viscosity | 1 - 100.000 mPas |
| Solids | not permitted |
| Gas content | 0 % |
| NPSH | ca. 2 m |
| Seal | GLRD / Magnetic Coupling |
This variant forms the backbone of many lubricating oil and hydraulic systems. When designing these systems, our engineers draw on many years of experience dating back to 1984 to calculate the optimal flank clearance for your specific operating viscosity. Our specialists pay particular attention to the material pairing of the housing and gears to ensure high process reliability at the customer’s facility, even under load cycling conditions. Through precise technical validation, we minimize internal leakage and maximize volumetric efficiency.
| NPSH | 3 - 5 m |
| Seal | Mechanical Seal / Packing |
| Volume flow rate Q | 1 - 2.500 l/min |
| Materials | GG25, GGG40, steel |
| Pressure | up to 120 bar |
| ATEX | Zones 1 & 2 are possible |
| Efficiency | 75 - 92 % |
| Performance | 0,5 - 150 kW |
| Rotational speed | 500 - 3.500 min⁻¹ |
| Temperature | -20 °C to +200 °C |
| Viscosity | 10 - 100.000 mPas |
| Solids | not permitted |
| Gas content | up to 5% for a short period |
Relevance for Engineers and Technical Buyers
The design is based on flow rate, differential pressure, viscosity, temperature, lubricity, rotational speed, and the permissible leakage and efficiency requirements of the entire system.
For technical procurement, the following must be clearly specified: flow rate parameters, materials, sealing and bearing designs, connection dimensions, temperature and pressure limits, as well as requirements for ATEX compliance, magnetic couplings, or variable-frequency drive operation.
Depending on the application, external gear pumps are designed and documented in accordance with relevant pressure equipment directives, ATEX requirements, material certifications, and project-specific functional, leak, and pressure tests.
FAQs by Industry
Select an industry
External Gear Pumps in Hydraulic Control Systems
Plastics Industry: Conveying Viscous Fluids
Transmission Technology: Handling of Lubricating Oils
Plastics Industry: Extrusion and Metering Technology
Chemical Industry: Production of Additives
Energy and Power Generation Industry: Process Safety
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