Product Viscosity and Filling Machines

When discussing product viscosity and filling machinery, the general rule is the higher the viscosity, the slower the flow of the product. Another way to think about product viscosity is the higher the viscosity, the thicker the product. It follows then, that different methods of filling will work better for different products based on their viscosity.


Thicker products simply do not flow as easily as thinner, or lower viscosity, products. For this reason, some assistance will usually be required not only to move the product through the filling machine pathway, but also to move it consistently and reliably to achieve the goals of the fill. In these cases, one of two types of filling machine will typically provide the best solution for filling products. The first is a pump filling machine, which as the name suggests, uses a pump to move product through the pathway and into the waiting containers. These machines use one pump for each fill head on the machine and the type of pump will be matched to the specific project to provide the best solution. A piston filler is the second type of filling machine that will often be used for highly viscous products. Again, as the name suggests, a piston is used to move product through the pathway when using this type of machine. The piston retracts to pull product into the cylinder, then pushes forward providing the extra help necessary to reliably move the thicker product. Though there are exceptions, pump and piston fillers will usually be the best solutions for highly viscous products.


Thin, free-flowing products, on the other hand, may need nothing more than gravity to achieve a consistent and reliable fill. Lower viscosity products may be pulled into a tank to use gravity or pressure-gravity to allow the product to flow into awaiting bottles on a time based system. In other words, nozzles simply open for a set amount of time, allowing product to flow from the higher tank into containers. Overflow filling machines provide a second option for thinner products, that allows bottles or other containers to be filled to a specific and consistent level. Thin products run through special nozzles that allow product to overflow back to the supply tank once the liquid reaches a certain level. Again, overflow fillers work better with thin products because of the ease with which the products flow. Just like the thicker products, exceptions will apply, but most lower viscosity products will be processed using gravity and overflow filling machines.


One example of an exception to the rule may stem from a product that includes particulates. For example, some free-flowing dressings or sauces may include grains, spices, vegetable pieces or other particulates. Without the particulates, the product may flow easily through a gravity or overflow machine. However, if the particulates are substantial in size, they may block the flow through the product pathway or become jammed in the nozzles, leading to inconsistent fills. In such a case, a piston filling machine may be used to move both product and particulates in a consistent manner.

Many other exceptions apply and each filling project will be analyzed on a case-by-case basis to find the best solution for the given project. If you have questions about your own filling needs, feel free to contact a packaging specialist at Liquid Packaging Solutions for assistance.