Filling "Unit-ology" 101 --

A Basic Course in FILAMATIC® Filling Units
FILAMATIC® Filling Units have been around for nearly fifty years. During that time, and through thousands of applications, they have evolved into a variety of forms designed to package just about any flowable material.

Each unit consists of five primary elements, as illustrated by the diagram to the right. Those elements are (1) the valve assembly, (2) the piston/cylinder assembly, (3) the intake tubing, (4) the discharge tubing, and (5) the nozzle assembly.

Usually, a Filling Unit's product contact surfaces are made with type 316 or 316L stainless steel and one or more elastomers such as Teflon® or silicone. However, we also make Filling Units with non-metallic product contact surfaces to handle free-flowing, corrosive or metal-sensitive liquids such as acids and reagents.

Determining which of the various Filling Unit types and sizes is the right one for a particular application is a five-step process that includes each of the elements mentioned above.
The initial step is choosing the appropriate type of valve assembly. Valve assemblies are available in four configurations including:
  • The combination of a valve ball and a valve weight.
  • The combination of a valve ball and a valve spring.
  • A pneumatically-operated spool valve.
  • An elastomeric duck-bill valve.

A discussion of the capabilities of the various valve assembly configurations follows immediately below and is summarized in Table 1.
The valve ball/spring configuration, which is also used in type FUS and FKS Filling Units, handles free flowing, low- to medium-viscosity liquids with or without fine particulate matter suspended in them. This valve configuration can accommodate a minimal amount (less than 5 PSI) of positive pressure in the product feed system.
The valve ball/weight configuration, found in type FUS and FKS Filling Units, is best suited for free flowing, low- to medium-viscosity liquids with no particulate matter. Additionally, there should be no positive pressure present in the product feed system.
The spool valve configuration is designed to work in type FSV Filling Units. It is used for free flowing/low viscosity to high viscosity materials with or without particulate matter ranging up to roughly 1/8" in size. This valve configuration is used when there is a moderate amount (up to approximately 30 PSI) of positive pressure in the product feed system. The duck-bill valve configuration, is perfect for free flowing/low viscosity, shear sensitive liquids with or without fine particulate matter. It is a standard feature of type KYU Filling Units and an option for type FUS Filling Units. This is another valve configuration that is designed for use in applications where there is no positive pressure present in the product feed system.
Typically, free flowing/low viscosity liquids are those with measurements of up to 100 centipoise (cps), and include products such as water-based reagents, colognes or perfumes, and chemicals like sulfuric acid, ethylene glycol, benzene, and acetone. Medium viscosity liquids usually range from 100 cps to 1,000 cps, and include products such as hand/body lotions,
Table 1
shampoos/conditioners, syrups and oils. High viscosity materials measure greater than 1,000 cps, and include products such as petroleum jelly, mustard and ketchup, agar media, mascara, and pastes.

Once you have determined the appropriate valve assembly, the second step is selecting the proper piston/cylinder assembly. Choosing a unit with an appropriate effective fill volume, or displacement range is important. The effective fill volume/displacement range is one in which you can expect a fill volume repeatability or accuracy of ±1% or better.

The upper limit of the range is the maximum fill volume or displacement of a Filling Unit. The upper limit is determined by the internal diameter of the cylinder and the maximum stroke length of the piston. The first number found in the model designation of a Filling Unit (e.g. FKS-130 or FKS/XL-560) indicates the maximum fill volume/displacement, as measured in milliliters (ml.) or cubic centimeters (cc.).

The lower limit of the range, or the minimum effective fill volume/displacement, is typically 5% or 10% of the maximum. For our "XL" designated Filling Units, the minimum effective fill volume/displacement is approximately 5% of the maximum fill volume/displacement. This gives an "XL" Filling Unit a recommended operating range ratio of roughly 20:1. It means an "FKS/XL-560" Filling Unit may be used for fill volumes ranging from 26 ml. to 560 ml. For a standard, or non-"XL", Filling Unit, the minimum

effective fill volume/ displacement is approximately 10% of the maximum fill volume/ displacement . So a standard Filling Unit has a recommended operating range ratio of roughly 10:1. For example, an "FKS-130" Filling Unit is best suited for use with fill volumes ranging from 13 ml. to 130 ml.

Table 2 provides a listing of the FUS, FKS, FSV, and KYU Filling Unit sizes that are available, along with the corresponding effective fill volume/displacement range.
Table 2
After determining the appropriate valve assembly and choosing the most appropriate effective fill volume/displacement range for a particular application, the third step in selecting a FILAMATIC® Filling Unit focuses on the seal between the piston head and the cylinder.

The standard seal configuration is a set of Teflon® packing rings (left, above) that can be used with most flowable materials. As normal wear occurs, you can tighten the adjustment stem to maintain the appropriate seal between the packing rings and the cylinder. One optional seal configuration uses an o-ring and an o-ring adapter (left, below) to replace the packing rings. The o-ring configuration is a more sanitary design and has proven to be more effective with many aqueous solutions, especially when a silicone o-ring is used.
The fourth step is the selection of the appropriate type of nozzle assembly. Most filling applications use one of two basic nozzle configurations. These configurations include (1) a straight-through, unobstructed flow nozzle (in National Instrument terminology, a type "DN" nozzle), and (2) a nozzle with a built-in check valve consisting of a valve ball and a valve spring (a type "DNV" nozzle).

Typically, as the viscosity and/or surface tension of the material increases, the more likely you are to need the type "DN" nozzle. By the same token, as the viscosity and/or the surface tension of the material decreases, the better the chances are that the type "DNV" nozzle is most appropriate.

The configuration of the optimum nozzle usually involves a series of compromises. For example, the larger the opening at the tip of the nozzle, the slower the material exits the nozzle and enters the container -- this is good. However, the larger the opening at the tip of the nozzle, the greater the probability that material will drip out of the nozzle when it isn't supposed to -- this is bad. But, if the nozzle's diameter is 3/8" or larger, a screen can be installed at the tip to help control dripping. One other thing to consider -- since most nozzles enter the containers during the filling process, another constraint on the size of the nozzle tip is the diameter of the opening in the neck of the container.
"DN"
"DNV"
The final step is selecting the appropriate intake and discharge tubing. Intake tubing must be able to resist collapsing inward from the suction force created during the intake cycle. When the intake tubing collapses, the filling unit can't draw in the appropriate amount of material and you get an under-filled container. Discharge tubing must be able to resist expansion caused by the pressure of the material being pushed through the nozzle into the container. When the discharge tubing expands, the material continues to dribble out of the nozzle after the filling cycle is finished.

A couple of other things to consider when selecting tubing are chemical and temperature compatibility. Chemical incompatibility between the tubing and the material, or incompatibility between the tubing and the temperature of the material during the filling process, can compromise the integrity of the tubing and lead to the problems mentioned above -- collapse of the intake tubing or expansion of the discharge tubing.

The standard intake/discharge tubing supplied by National Instrument is nylon-reinforced PVC tubing. This tubing has extremely good chemical and temperature tolerances and is suitable for most filling applications.

While these guidelines provide a way to identify which components are suitable for certain filling applications, they are only guidelines. Material characteristics or properties other than those mentioned above may affect the type of valve assembly, seal configuration, nozzle assembly, and flexible tubing you should use. The only foolproof way to identify the right Filling Unit for a specific application is to perform fill testing using the actual liquids involved. A cost-effective way to find the optimum FILAMATIC® Filling Unit type/size for your application is to add our product testing/evaluation technicians to your team. If you would like to read a detailed discussion of how our testing and evaluation service works, click here.