Overflow and Gravity - Filling to a Level or Filling By Volume
Overflow filling machines and gravity fillers are two of the most manufactured pieces of machinery at Liquid Packaging Solutions. While they are similar in that they are normally used for thin and free-flowing products, the differ greatly in how they get the liquid in to the containers. This difference is one that LPS likes to revisit about once a year, as the fill principles will work better for certain products, industries or projects.
Gravity filling machines are one of several liquid fillers that fill by volume. In other words, a specific amount of product, or liquid, will go in to each container. For these bottle fillers, product will be held in an overhead tank, and the fill is, in essence, a timed fill. Nozzles will open for a preset amount of time, and gravity will force the liquid from the tank in to the waiting containers. Each nozzle can be timed individually to ensure an accurate volume for those machines with multiple fill heads. While the volume will be the same in each bottle, the levels may vary slightly if the interior volume of the containers varies. For many products, this may not be an issue, but for packagers using clear containers, different levels may create an odd appearance on the shelf and even leave some consumers questioning if they are getting all of the product that they deserve.
The overflow filler can handle many of the same products that can be run on a gravity filling machine. However, the overflow filler does not fill by volume. Instead, this liquid filler uses a unique nozzle to ensure that each and every container is filled to the same level, regardless of interior volume. For packagers with clear bottles, this can increase aesthetic value when the bottles are lined up on the shelf for consumers, solving the issue noted above. Overflow nozzles descend to create a seal on the bottle opening. Once the seal is created, liquid flows in to the bottle until it reaches the desired level. Any additional liquid is typically recirculated back to the holding tank, eliminating product waste while also creating the level fill.
Of course, some industries need to be highly accurate on their volumes, such as distilled spirits. But even those industries will usually have a range that will be met. So even if specific volumes must be met, the overflow filler can still be a solution. In working with a number of industries, products and bottles, LPS has found that most of the time the bottle manufacturers are consistent in the production of containers. However, if volume is a concern and an overflow filler is used, a packager will want to ensure that the interior volume of the containers being used is consistent enough to hit target volumes.
Of course, other factors may come in to play when deciding between a gravity filling machine and an overflow filler, including the product itself, the container sizes, the container types and more. To learn more about these and other liquid fillers, or for assistance identifying the best filling machine for a project, simply contact LPS to discuss specific project details!