How Do Gear Pump Fillers Work?

Once you know, you may specify gear pump fillers more often because of their simplicity and accuracy in filling liquids.

John R. Henry

May 2, 2024

2 Min Read
Filling line
Avatar_023 / iStock via Getty Images Plus

At a Glance

  • A gear pump's consistency provides high-precision liquid filling.
  • A gear pump's single valve simplifies its operation.

Volumetric fillers measure the amount of liquid filled into the container regardless of container size. Pistons are the most popular type. Gear pump fillers are probably second. Here’s how gear pump fillers work:


Gear pumps have long been used for transfer of liquids and semi-liquids, from non-viscous to heavy greases and the like. They are positive displacement, meaning that for every revolution, a consistent amount of liquid is moved. This consistency makes them ideal for high precision liquid filling. A pump, which will dispense 100 milliliters per revolution, will reliably dispense 50ml per half a revolution or 200ml for two revolutions.

Gear pumps consist of two intermeshing gears. As the gears rotate, they trap product between the teeth. As the gears mesh in the center of the pump, product is forced out the pump discharge. The amount of product discharged is determined by the size of the gap between the teeth and the amount of rotation.


When used in liquid filling applications, the pump is driven by a servo motor. The servo motor, with its controls, allows precise control of the total pump rotation. It also allows precise control of the filling speed and acceleration/deceleration independently of the rest of the filling machine. Dynamic, electronic, braking stops the pump precisely.

Piston pumps need to refill after every dispense. This limits their speed. Gear pumps only run in one direction. This allows them to cycle constantly with virtually no delay between fill cycles. One application dispensed a drop of fragrance into a bleach bottle at 200 parts per million. Piston pumps need two valves to control infeed and discharge. A gear pump only needs a single valve. This simplifies mechanisms and plumbing. 

A variation replaces the gear pump with a circumferential piston (Waukesha style) pump or with lobe pumps. This allows gentle handling of chunky products, such as cherry pie filling, without damaging the chunks.

When selecting a new filler, be sure to consider the gear pump alternative.

It’s easy when you know.

Find out more about packaging machinery and how it works in my Packaging Machinery Handbook. Chapters cover filling, flexible packaging, coding, and all commonly used packaging machinery. The complete table of contents and chapter samples can be found at

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About the Author(s)

John R. Henry

Known as the Changeover Wizard, John R. Henry is the owner of, a consulting firm that helps companies find and fix the causes of inefficiencies in their packaging operations. He has written the book, literally, on packaging machinery ( and is the face and personality behind packaging detective KC Boxbottom, the main character in popular articles on the Packaging Digest website. He can be contacted at [email protected].

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