Few components in the hydraulic world have stood the test of time the way internal and external gear pump have. Even with the rise of energy-efficient servo systems, digital control valves, and high-precision motion technologies, gear pumps continue to be the trusted choice for industries ranging from construction machinery to manufacturing to mobile hydraulics.

There’s a simple reason for that:
They are reliable, efficient, cost-effective, and versatile—a combination that’s becoming rare in today’s increasingly complex fluid-power world.

If you are an engineer, machine designer, maintenance technician, or simply studying hydraulic systems, understanding the strengths of both internal gear pumps and external gear pumps will help you select better systems, improve energy efficiency, and reduce downtime.

This blog gives you a complete, human-friendly, real-world explanation of both pump types, how they differ, where each one fits, and how newer technologies like hydraulic motor pump systems and small servo motors and drives pair with them in modern equipment.

Grab a coffee, and let’s dive in.

Understanding the Basics: What Makes Gear Pumps So Reliable?

All hydraulic pumps work by creating a vacuum at the inlet so oil is drawn in, and then pushing that oil into the hydraulic system under pressure.

Gear pumps—whether internal or external—do this using rotating gears.

Even when other pump types like vane, axial piston, and radial piston pumps entered the market, gear pumps remained widely used because they are:

• Mechanically simple

• Low in cost compared to variable-displacement pumps

• Durable in harsh environments

• Capable of handling different viscosity fluids

• Easy to maintain and repair

They have fewer moving parts, which means fewer things that can go wrong.

But internal and external gear pumps are not identical—they solve different problems.

External Gear Pumps: The Workhorse of Industrial Hydraulics

An external gear pump uses two identical gears that rotate against each other—one is driven by the motor, the other rotates freely (idles). Oil is trapped between the gear teeth and pumped to the outlet.

Where External Gear Pumps Shine

External gear pumps are known for:

High durability: They are built to withstand dirtier oils and tough operating environments.
High-pressure capability: Many can operate up to 250–300 bar depending on design.
Compact construction: Their small footprint allows them to fit into tight spaces in mobile equipment.
Affordability: Their simple design makes them cheaper to produce and maintain.
Ideal for hydraulic motor pump systems: Because they can handle high-speed rotations, they pair well with motor-driven hydraulic systems.

Common Applications

• Forklifts

• Tractors and agricultural machinery

• Mobile hydraulic equipment

• Lubrication systems

• Chemical processing

• Hydraulic power packs

The robust power-to-size ratio of external gear pumps makes them perfect for applications where equipment must be compact but powerful.

Internal Gear Pumps: The Smooth, Quiet, High-Precision Alternative

If external gear pumps are the “workhorse,” internal gear pumps are the “smooth operator.”

They consist of an internal gear (the rotor) that meshes with a larger external gear (the idler). This offset arrangement creates chambers that transport hydraulic fluid.

Advantages of Internal Gear Pumps

Internal gear pumps offer several benefits that make them ideal for precision hydraulics:

 Extremely quiet operation: Their meshing design naturally reduces noise and vibration.
Wide fluid compatibility: They work well with thick fluids, low-viscosity oils, and even  some chemicals.
Excellent suction capability: Perfect for low-speed, high-torque environments.
Smooth flow: They deliver consistent flow with minimal pulsation—great for sensitive systems.
Easy maintenance: Fewer components and slower internal speeds result in long service life.

Industries That Rely on Internal Gear Pumps

• Plastic molding machines

• Hydraulic presses

• Food processing (for pumping oils & syrups)

• Chemical plants

• Mobile machinery needing low noise

• Energy-efficient servo hydraulic systems

Whenever a machine requires quiet operation, stable flow, and long-term reliability, internal gear pumps often become the top choice.

Internal vs External Gear Pumps: Choosing the Right One

Most engineers eventually face this choice: internal or external?

Here’s a more human, real-world way to think about it.

Pick an internal gear pump when:

• You need quiet operation

• Flow precision matters

• The fluid is thick, sticky, or abrasive

• Long operating hours are expected

• The system is servo-controlled or uses proportional valves

• You need low noise for indoor or operator-friendly environments

Pick an external gear pump when:

• You need high pressure in a compact package

• The budget is tight

• The environment is harsh

• You work with standard hydraulic oils

• The equipment is mobile and exposed to vibration

• You want a low-cost hydraulic motor pump solution

Both pump types are excellent—but each solves a different engineering challenge.

Where Modern Technology Fits In: Servo Motors, Drives & Pump-Motor Units

The hydraulic industry is rapidly shifting toward energy-efficient systems. This is where small servo motors and drives come into the picture.

Traditional hydraulic pumps run continuously at a fixed speed, even when demand is low. But servo-driven hydraulic systems solve this wastefulness.

How Servo Technology Transforms Gear Pump Performance

A servo motor + drive + gear pump combination creates a highly efficient, intelligent hydraulic power unit.

This setup gives you:

1. Variable speed on demand
The servo motor adjusts speed to match hydraulic load. During idle, it slows down, saving energy.

2. Higher system precision
Flow rate changes are instant and accurate—perfect for injection molding, CNC machinery, and press systems.

3. Low noise operation
Internal gear pumps + servo drives = incredibly quiet hydraulics.

4. Extended pump life
Lower average operating speeds reduce wear and tear.

5. Energy savings up to 70%
Real-world factories report major electricity savings using servo-hydraulic pump systems.

Because of these advantages, internal gear pumps are widely used inside servo hydraulic systems, while external gear pumps often power high-speed, cost-efficient setups.

Hydraulic Motor Pump Systems: Why Gear Pumps Are Still a Favorite

Hydraulic motor pump units—where a hydraulic motor drives a pump—are used in industrial automation, mobile machinery, and generator systems.

Gear pumps fit perfectly here because they:

• Handle continuous high-speed rotation

• Run smoothly even in high-vibration environments

• Offer long service life with low maintenance

• Work with compact motors, including small servo motors and drives

• Provide stable output flow even at high RPM

Whether powered by electric motors, servos, or diesel-driven hydraulic motors, gear pumps maintain performance where more delicate pumps might fail.

Real-World Problem Solving: When a Gear Pump Becomes the Best Decision

Let’s consider a few real-world situations:

1. A factory struggling with noise complaints

Switching from an external gear pump to an internal gear pump with a servo motor drastically reduces noise. Operators feel more comfortable, and machines comply with noise regulations.

2. A construction machine needing powerful hydraulics in a cramped space

An external gear pump can deliver high pressure in a compact design without overheating or requiring large motors.

3. A plastic molding machine needing precise, consistent injection pressure

Internal gear pumps deliver smooth, low-pulsation flow—critical for product quality.

4. A plant facing high electricity bills due to constantly running pumps

Servo drives paired with internal gear pumps reduce energy consumption during idle cycles.

5. A mobile hydraulic system needing maintenance-free performance

External gear pumps are rugged enough to handle unpredictable outdoor conditions.

In every case, understanding the strengths of internal and external gear pumps makes system design more efficient and cost-effective.

Tips for Getting the Most Out of Any Gear Pump

Here’s a set of practical, experience-based suggestions to extend pump life and improve reliability:

Choose the correct viscosity: Gear pumps perform best when the oil matches manufacturer recommendations.
Avoid cavitation: Ensure proper inlet conditions—adequate piping size, minimal restrictions, and clean filters.
Keep the oil clean: Contaminants are the biggest enemy of all hydraulic components.
Don’t overspeed the pump: Gear pumps can handle high RPM, but staying within limits avoids early wear.
Monitor noise changes: A sudden increase in noise is often the first sign of wear.
Pair pumps with modern drives when possible: small servo motors and drives significantly reduce operating cost.

Simple steps, but they add years to your system.

Conclusion: Gear Pumps Remain Essential—And Their Future Is Even More Promising

Even as hydraulic technology advances rapidly, internal and external gear pumps remain indispensable due to their simplicity, affordability, reliability, and adaptability.

Internal gear pumps provide quiet, smooth, and precise flow for demanding industrial applications.
External gear pumps deliver rugged, compact, and cost-efficient power for mobile and general-purpose systems.

Combined with small servo motors and drives, gear pumps have become more efficient and intelligent than ever. And as sustainable, energy-saving hydraulic solutions continue to grow, gear pumps will remain at the heart of the most innovative systems.

If you’re designing or upgrading hydraulic equipment, selecting the right gear pump can dramatically improve performance, reliability, and energy efficiency. And with proper pairing and maintenance, these pumps can serve your machinery for years with minimal downtime.

FAQs

1. What is the main difference between internal and external gear pumps?

Internal gear pumps are quieter and provide smoother flow, while external gear pumps are more rugged and suitable for high-pressure applications.

2. Are internal gear pumps better for servo-driven hydraulic systems?

Yes. Their smooth flow and quiet operation make them ideal for pairing with servo motors and drives.

3. Where are external gear pumps typically used?

They are commonly used in mobile machinery, forklifts, tractors, hydraulic power packs, and general industrial systems.

4. Do gear pumps handle thick fluids well?

Internal gear pumps perform exceptionally well with high-viscosity fluids, making them suitable for oils, resins, syrups, and certain chemicals.

5. Can gear pumps be used in hydraulic motor pump units?

Absolutely. Their durability and high-speed capability make them perfect for hydraulic motor-driven systems.

6. Are gear pumps easy to maintain?

Yes. Their simple design means fewer components, less wear, and easier repairs.

7. How do servo motors improve hydraulic pump performance?

Servo motors adjust speed based on load demand, lowering noise, reducing energy consumption, and extending pump life.