The Technologies Behind Liquid Filling

First Published: May 20, 2024
Channel: Technology

In the world of packaging, filling liquids into bottles is a critical step that demands precision, efficiency, and flexibility. From beverages and pharmaceuticals to chemicals and cosmetics, the type of filler used can significantly impact the quality and speed of the production process. Let’s explore the various technologies used for filling liquids into bottles, focusing on the different types of liquid fillers, including linear and rotary models.

Types of Liquid Fillers

Liquid fillers are categorized based on their operation type and the kinds of liquid they handle, particularly concerning the viscosity and whether the liquid is carbonated. Here are the main types that are commonly in use:

Gravity Fillers

Pressure Fillers

Pump Fillers

Piston Fillers

Vacuum Fillers

Overflow Fillers

Linear vs. Rotary Fillers

Gravity Fillers

Gravity fillers use gravity to transfer liquid from a storage tank into bottles. When the valve is opened, the liquid flows through it and into the bottle. The amount of liquid filled is controlled by timing how long the valve is opened.

Gravity Fillers Include Simple Semi-Automatic Machines & Sophisticated Rotary Equipment (Fogg Filler)

In some cases, gravity fillers can be configured as net-weight fillers, where each container is weighed before filling, and the liquid is filled until the required weight is achieved.

Common Products Filled:

– Water: Still water and mineral water.

– Juices: Non-viscous fruit juices without pulp.

– Thin Sauces: Soy sauce, vinegar and similar.


– Simple and cost-effective.

– Suitable for non-viscous liquids.

– Gentle on the product, preserving its quality.


– Limited to low-viscosity liquids.

– Slower filling speeds compared to other methods – although this can be compensated for by adding more filling heads in either linear or rotary configurations.

Pressure Fillers

Pressure fillers use air pressure to push the liquid into the bottles, rather than it being free-flowing from a tank with gravity fillers. These fillers can be further divided into pure pressure fillers and counter-pressure fillers.

Here’s a comparison to help understand the differences:

Pressure Fillers

How They Work:

  • Pressure fillers use a pump to force the liquid into the container.
  • The liquid is pushed into the container at a pressure higher than atmospheric pressure.

Best For:

  • Non-carbonated liquids, such as water, juices, and dairy products.
  • Products that are not sensitive to foaming or carbonation loss.

Key Features:

  • Simple design and operation.
  • Cost-effective for non-carbonated products.
  • They are less sophisticated than counter-pressure fillers, making them easier to maintain and operate.

Counter-Pressure Fillers

How They Work:

  • Counter-pressure fillers use a two-step process to fill the container: The container is first pressurized with CO2 or another inert gas to match the pressure of the liquid being filled.
  • The liquid is then filled into the container under pressure, minimizing turbulence and foaming.

Best For:

  • Carbonated beverages, such as beer, soda, and sparkling water.
  • Products that are sensitive to carbonation loss and foaming.

Key Features:

  • More complex and precise filling process.
  • Ensures minimal loss of carbonation and reduces foaming.
  • Typically, counter-pressure fillers are more expensive and require more maintenance than pressure fillers.
  • Often, they have additional features like pre-evacuation and purging with inert gas to further protect the product’s quality.

Practical Example

Consider filling a bottle of soda versus filling a bottle of juice. For the juice, a pressure filler would efficiently fill the bottle without concern for carbonation. However, if you used a pressure filler for soda, the rapid filling and pressure difference would cause excessive foaming and carbonation loss, resulting in a flat beverage.

On the other hand, a counter-pressure filler would gently fill the soda bottle under controlled pressure, preserving its carbonization and ensuring a high-quality product.

Pump Fillers

Pump fillers utilize various types of pumps (gear, lobe, diaphragm, or peristaltic) to move the liquid into the bottles.

The product is filled into the container under carefully controlled pressure, allowing products with higher viscosities to be successfully filled.

Pump fillers can accurately dispense small volumes of high-value products and are often used for small packages of pharmaceuticals or cosmetics.

Common Products Filled:

– Cosmetics: Lotions, creams, shampoos.

– Pharmaceuticals: Medicinal syrups, ointments.

– Chemicals: Cleaning solutions, motor oils.


– Highly versatile, handling a wide range of viscosities.

– Precise control over fill volume.

– Suitable for both low and high-viscosity products.


– More expensive and complex than gravity and pressure fillers.

– Requires maintenance of pumps and associated components.

Piston Fillers

Piston fillers draw the liquid into a cylinder and push it into the bottle using a piston. They are ideal for highly viscous products.

Semiautomtic Piston Filler – Source: Allpack Process & Packaging

The amount of product filled into the container is determined by the volume of the cylinder, making these fillers very precise.

Common Products Filled:

– Food Products: Honey, peanut butter, jams, and jellies.

– Cosmetics: Heavy creams, gels.

– Industrial Products: Greases, adhesives.


– Excellent accuracy and consistency.

– Can handle very thick and particulate-filled products.

– Easy to clean and maintain.


– Slower than some other technologies because of the two-stage filling cycle.

– Not suitable for low-viscosity liquids.

Vacuum Fillers

Vacuum fillers create a vacuum in the bottle to pull the liquid in. This method is often used for filling glass bottles with liquids that are not prone to foaming.

How a Vaccum Filling Machine Works – Universal Filling Machine

Common Products Filled:

– Perfumes: Essential oils, fragrances.

– Alcoholic Beverages: Wines, spirits.

– Specialty Oils: Olive oil, gourmet oils.


– Precise fill levels.

– Suitable for delicate, high-value liquids.

– Minimal contact with air, preserving product quality.


– Limited to non-foaming, medium to low viscosity liquids.

– Higher initial cost and complexity.

Overflow Fillers

Overflow fillers ensure that each bottle is filled to the same level, which is particularly important for products in transparent bottles where consistent appearance matters.

Overflow Filler Operation – Source: Inline Filling Systems

Overflow fillers can utilize various filling technologies, such as gravity, pressure or vacuum and they compensate for changes in bottle volume by always filling to the exact level – the liquid is filled slightly higher than the required level and the excess is then removed from the bottle and recycled through the filling system.

Common Products Filled:

– Beverages Packed in. Clear Containers: Bottled water, juices.

– Liquid Soaps: Hand soap, dishwashing liquids.

– Household Chemicals: Cleaners, disinfectants.


– Consistent fill levels across all bottles.

– Suitable for both thin and moderately viscous liquids.

– Ideal for products where visual consistency is important.


– Not suitable for very high-viscosity products.

– May require adjustment for different bottle sizes.

Linear vs. Rotary Fillers

The operational configuration of liquid fillers can be broadly divided into linear and rotary models, each suited for different production volumes and complexities.

Linear Fillers

Linear fillers, as the name suggests, fill bottles arranged in a straight line. The bottles move along a conveyor, stopping at filling stations to receive the liquid. These systems are generally simpler and more flexible, making them suitable for smaller production runs or frequent product changeovers.

Linear 4-Head Filling System – Source: Universal Filling Machines

In operation, the flow of bottles is arrested, and a number of them (to coincide with the number of filling heads) is allowed to pass into the machine.

When the bottles are filled, they are released to the next station in the packaging line, and the process is repeated.

Advantages of Linear Fillers:

– Flexibility in handling different bottle shapes and sizes.

– Easier to set up and adjust – change parts are often not required.

– Lower initial investment and maintenance costs.

Ideal Applications:

– Small to medium-sized production lines.

– Facilities that require frequent product changeovers.

– Specialty products with unique bottle designs.

Rotary Fillers

Rotary fillers feature a rotating turret with multiple filling heads, allowing bottles to be filled continuously as they move through the system. This design is highly efficient and suitable for high-speed, large-volume production.

High-Speed KHS Filler for Beer Filling

Advantages of Rotary Fillers:

– High throughput and efficiency.

– Consistent fill levels and precise volume control.

– Suitable for large-scale production with minimal downtime.

Ideal Applications:

– Large-scale beverage, dairy, and pharmaceutical industries.

– High-speed production lines with minimal variation in bottle size and shape.

– Continuous, round-the-clock operations.

Choosing the Right Filler

Selecting the appropriate filling technology depends on several factors, including the type of liquid, production volume, bottle design, and budget. Here are some considerations to keep in mind:

Liquid Characteristics: Viscosity, foaming tendency, and the need for carbonation.

Production Volume: High-volume lines benefit from the speed of rotary fillers, while linear fillers are better for smaller batches.

Bottle Design: Unique shapes and sizes might require the flexibility of linear fillers.

Accuracy and Consistency: Products needing precise fill volumes or levels may dictate the choice of filler type.

Budget: Initial investment, maintenance costs, and the potential for future scalability should all be factored in.

Systems for in-place cleaning (CIP) that are needed when products need to be changed and at the end of production runs.

Environmental ingress (IP) protection for use in damp or dusty environments.


Understanding the various technologies for filling liquids into bottles is crucial for optimizing your production line. Whether opting for the flexibility of linear fillers or the high-speed efficiency of rotary fillers, choosing the right equipment can enhance productivity, maintain product quality, and ensure cost-effectiveness. As the packaging industry continues to evolve, staying informed about the latest advancements in filling technology will help you stay ahead in a competitive market.

Further Reading

Should you fill packages by level or volume? By John Henry for Packaging Digest

Liquid Filling in Focus – a video from PMMI’s Emerging Brands Alliance

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