How do you achieve an accurate volumetric fill?
One definition of the word volume is amount. So, to put it simply, when a packager desires a volumetric fill, that packager is looking to put the same amount in to each container that is filled. This differs from other filling principles such as the overflow filler that will fill each bottle to the same level or a net weight filler that will fill based each container until a target weight has been met. There are several different ways to achieve an accurate volumetric fill with the best choice often depending on the product or products involved in the packaging process.
Gravity Filling Machines
As the name suggests, these liquid fillers take advantage of a resource available to everyone, namely gravity. When using a gravity filler, product will be held in a tank above the fill heads. Once the bottles are in place, valves will open to allow product to flow from the tank in to the waiting containers. The valves remain open for a specific amount of time each cycle to ensure consistent volume in each bottle. On LPS models, each individual head can be set using a timer to ensure a higher accuracy and reliability on these fills. Given that gravity is the only force in play on such bottle fillers, this solution is usually limited to lower viscosity, free-flowing liquids.
Pump Filling Machines
Pump filling machines allow for a volumetric fill for higher viscosity products by using a pump to assist in the movement of the product. Much like the gravity filler, valves or fill heads may open for a set amount of time to allow product to flow in to waiting containers, but rather than rely just on the force of gravity, the pumps will push the product in to the containers, with pumps being matched to each specific product to achieve the best results. However, in some cases pump filling machines may rely on the movement of a component of the pump rather than a specific time. For instance, a gear pump will collect a specific amount, or volume, or product between its cogs or gears. The fill may be based on the turning of these gears, also known as a pulse, to reach the desired volumetric output of product. A pulse may be a half turn, full turn or other repeated movement of the gears in the pump depending on the amount of product needed to be dispersed.
Piston Filling Machines
Finally, piston fillers also provide highly accurate fills by volume for products both thick and thin. With this type of filler, a cylinder is filled with product before being displaced by a piston and pushed in to the containers to be filled. As the internal volume of the cylinder never changes, the volume of product dropped in to the containers will also never change. The openness of the cylinder (versus tubing on other machines) makes the piston filler ideal for thick products also, as well as products that may have significant particulates such as fruits or vegetables found in some jams and sauces.
Each of these volumetric filling machines has advantages and disadvantages depending on the product, containers, speed desired and other factors. But for packagers desiring a volumetric fill, there will almost always exist an ideal solution in one of the three machines listed above. To learn more about volumetric fills and other filling principles, contact a Packaging Specialist at Liquid Packaging Solutions to discuss your project today.