Gravity vs. Overflow - Two Ways to Fill Free-Flowing Products

When looking for a filling machine for free-flowing products, a packager will likely come across a variety of different liquid fillers. Two of the most popular for low viscosity liquids are the gravity filler and the overflow filling machine. While handling the same product types, each machine offers a unique way of completing the fill.

Gravity filling machines offer a simple way to achieve an accurate volumetric fill. Product is held in a tank above the fill heads and, as the name suggests, gravity is used to move product into the waiting bottles. Valves will open and close according to pre-set times during which liquid will be released to allow each bottle to reach the desired volume. On LPS machines, the fill time (or time that the valve is open to allow product in) can be set for each individual head, allowing for added accuracy.

The overflow filler allows an alternative to a volumetric fill by filling each container to the same level, even if the internal volume of the bottles is slightly different. This type of fill is ideal for clear or nearly clear containers, allowing for a clean, aesthetically pleasing look when the product reaches the shelf. The overflow filler uses a unique filling nozzle that seals over the container opening. Product is then released into the container and will "overflow" back to the holding tank through a second port on the overflow nozzle when the desired level is reached. The recirculation of liquid also helps to reduce product waste.

While other filling machines may be used for free-flowing or low viscosity products, the gravity and overflow options will probably be seen more than any other fill principle. Both types of filling machines are available in semi-automatic and automatic models for packagers with low, medium or high demand. Automatic machinery uses an indexing system and a PLC to move bottles in and out of the fill area without the assistance of an operator for each cycle. Semi-automatic machinery will require an operator to move bottles and initiate the fill with each cycle. Gravity and overflow fillers both use multiple fill heads where needed for added efficiency in filling bottles.

Visit the Gravity Fillers or Overflow Fillers page of the Liquid Packaging Solutions website for more information on either type of filling machine, or call an LPS packaging specialist to learn about all filler options and discuss the best solution for your own project.