Gerotor Pump Advantages and Disadvantages

Consistency, efficiency, and versatility. 

When asked what sets gerotor pumps apart from other pumps, these are the answers. 

Gerotor pumps have been around for more than a century as a preferred method of pumping fluids. In this blog, we’ll discuss the gerotor pumps advantages and disadvantages, as well as when gerotor pumps are best.

What Are Gerotor Pumps?

Before diving into the advantages and disadvantages of gerotor pumps, understanding what gerotor pumps are and how they work is essential. 

We’ll start with the basics. What are gerotor pumps?

They’re positive displacement pumps used to pump fluids of nearly any viscosity. Broken down, gerotor pumps consist of rotating inner and outer gears.

As the inner and outer gears rotate, the space between the inner and outer gear profile increases creating suction and drawing fluid into the pumping chambers. As rotation continues, the space between the inner and outer gear profile decreases and the fluid is pushed out.

Advantages of Gerotor Pumps

There are several positive displacement pumps to choose from. What are the advantages of gerotor pumps?

1. Consistent, constant fluid distribution
2. Simple operation & functionality
3. High efficiency
4. Extreme versatility from gerotors

1. Consistent, Constant Fluid Distribution

Regardless of viscosity, a gerotor pump maintains a constant and consistent fluid distribution. Gerotor pumps pump oil, water, or even fuels with minimal leakage, maintaining a near-

constant volume of fluid displacement per revolution across a broad range of outlet pressure.

2. Simple Operation & Functionality

While gerotors are complex structures, the functionality is pretty straightforward. Gerotor pumps function in either direction and are relatively quiet. With only two moving parts, the chance of parts breaking or malfunctioning is much less than other pumps – resulting in low maintenance and repair costs.

As a low-cost, quiet way to pump fluid, gerotor pumps are highly sought after in applications for vehicles and aircraft.

3. High Efficiency

Due to their design, gerotor pumps are highly efficient. With large teeth that allow fluid to flow smoothly, there is low vibration during the process – resulting in minimal wear and tear as well as lower energy consumption.

The overall compact size of the gerotor pump also ensures efficiency. These pumps only hold a specific amount of fluid, so the energy to operate is much less than in larger pumps.

4. Extreme Versatility from Gerotors

The versatility of gerotors is one of the main advantages of gerotor pumps. Gerotors have the ability to be mounted directly on an existing shaft or be driven via the outer rotor. 

They can be packaged easily into a large system, such as an engine or a transmission. Due to their ability to build suction pressure, they need not be submerged in a fluid sump – in fact, gerotors are an excellent choice for lifting liquids from a tank and pulling it through hoses or internal channels.

On the other hand, internally, a single gerotor set can accommodate multiple inlet flow streams operating at different pressures.

Disadvantages of Gerotor Pumps

Although gerotor pumps are ideal for several applications, there are three main disadvantages to the process: 

1. Unable to process solid inputs
2. Limited scalability
3. Fixed clearances

1. Unable to Process Solid Inputs

While gerotor pumps handle fluids of nearly any viscosity, they can’t process solid inputs. The gears of gerotor pumps are meant to rotate smoothly and quickly. If a solid is inputted, the gears can get stuck or shift, resulting in potential damage, wear and tear, and inefficient processes.

2. Limited Scalability

All pumps have size limitations. No matter the size of the pump, the amount of fluid can’t exceed the pump cavity’s volume capacity.

How does this affect the flow rate? 

For any application, the maximum flow rate that the pump can supply is its RPM

multiplied by its displacement. A pump that is spinning too slow will be extremely

inefficient, or fail to support its internal journal bearings. 

Speeding the pump up, a limit will be reached when the tip speed of the gear set is so high that fluid does not fill the inlet. It is crucial to identify the optimal speed for a gerotor pump – or conversely, the optimal gerotor pump for a given application.

3. Fixed Clearances

In gerotor pumps, the distance between the inner and outer rotor and the fixed surfaces on

either side is known as axial clearance. Inner and outer rotors also have a radial clearance. These clearances are defined when a gerotor pumping element is designed into a pocket in a

pump housing.

When the clearance is too large, a significant quantity of fluid can leak from high pressure regions to low-pressure regions, resulting in decreased volumetric efficiency. When the clearance is too small, especially in relation to the pumped fluid’s viscosity, much of the torque input to the gear set is used for simply overcoming the fluid drag, resulting in decreased mechanical efficiency.

Pro Tip! In pumps, the chance of decreased efficiency and increased leaks is high. Regularly keeping up with pump maintenance is important to avoid leaks and decreases in efficiency.

When Gerotor Pumps Are Best

When choosing a pump for an application, it’s usually based on ease of packaging and optimizing efficiency.

Since gerotor pumps are compact to package, energy efficient, and quiet, they are the preferred pump choice in many industries, most notably aerospace and automotive. 

For applications in both, fuel and oil need to be pumped through engine systems with minimal environmental impact, and high efficiency.

Gerotor Pumps Moving Forward

As a consistent, efficient way to pump fluids for over a century, gerotor pumps will remain a viable option in many industries for years to come. 

With its efficiency and other advantages, gerotor pumps bring a new level of optimization to an application.

Ready to Choose a Pump? 

Weighing your options when selecting a pump is difficult. Consult with one of our specialists to ensure you’re making the correct decision.