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, materials, and typical applications

• Advantages and disadvantages of external gear pumps

• The external gear pumps by Fluid-o-Tech

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Main features of external and internal gear pumps

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.

How does an external gear pump work?

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.

Design of gears, materials, and typical applications

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 commonly used in precision control and analytical applications where accurate dosing is required:
• Automotive
• Food Service
• Health Tech
• Paints and Inks

Ideal also for lubrication, recirculation, and metering applications.

Advantages and disadvantages of external gear pumps

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 talking about 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, in order 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

The external gear pumps by Fluid-o-Tech

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:

• direct 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.

Contact us to find out all our smart solutions