External Gear Pumps

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


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 gear (driven) driving gear driving 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. Fluid trapped between the gears are transmitted from the inlet to 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 teeth has an identical helix angle (referenced to the axias of rotation) such that 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
- Medical
- Paints and Inks

Ideal also for lubrication, recirculation and metering applications.

Advantages and disadvantages of external gear pumps

The advantages of external gear pumps are

- stable fluid stream with low pressure pulsations
- high accuracy
- reversible
- excellent suction capability
- well suited to pumping hazardous or hygienic fluids
- compact size
- long life

The disadvantages of external gear pumps:

- the gears should not be run dry for prolonged periods
- less suited to handling abrasive fluids having four bearings in the pumped medium, and tight tolerances
- no solids allowed

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 partnerfor 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.
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.

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