A Liquid Filler for Small and Medium Sized Operations

Inline Filling Systems designs and manufactures world class Filling Machine Equipment, Capping Machines, Labeling Machines, Turntables, Conveyors and other equipment for fully integrated liquid packaging lines.

This analysis deals primarily with a lower capacity liquid filler used by small to medium sized companies and excludes high speed rotary liquid fillers typically found only in the mass market beverage industry. In contrast, the liquid fillers discussed here are used throughout all industries including food, beverage, chemical, cosmetic and pharmaceutical but at lower speeds; usually less than 200 containers per minute. In fact, most of the market for a liquid filler in terms of units sold is for semi automatic equipment that operates at speeds not exceeding 20 containers per minute.

No one type of filling machine can handle all liquids in all industries. For example, a machine that fills bottled water cannot fill cosmetic cold cream. Nor would a chemical duty filler be used to fill pharmaceutical grade or dairy products.  Although there are many different types of filling technologies, there are relatively few that are versatile, practical and cost effective to own and operate. The choice of filling machine depends on the range of viscosities, temperature, chemical compatibility, particulate size, foam characteristics, and hazardous environment considerations. Each one of the machines below is discussed with its strengths and weaknesses and range of best suited applications.

Overflow liquid filler
This type of filler is perhaps the most widely used machine in small bottle filling operations because it handles a wide range of thin, free flowing liquids as well as liquids with medium viscosity. This machine is also commonly referred to as a "fill to level" filling machine or cosmetic height filler. This means that machine fills to a target fill height in the container rather than volumetrically. But it can also be shown that as long as the container specification do not vary greatly, the volumetric accuracy of this machine is excellent.

Because this filler operates in a closed loop basis, it is also ideal for handling foamy products.  The Examples of products that work well in this filler are bottled water, liquid soap, motor oil, cleansers and even some dairy products. It can be constructed in both chemical duty versions as well as sanitary versions capable of filling pasteurized products at high temperatures.

This machine is relatively low cost and easy to use. However it is generally not useable for products with viscosities greater than 25000 centipose or products that have any particulates exceeding approximately 1/16" diameter.

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Servo Pump liquid filler
This is a very versatile filling machine capable of filling nearly any type of product that can be pumped. Each nozzle has a dedicated servo controlled pump that can deliver thin liquids, medium and thick viscosity liquids, and liquids with large particulates. Because it is so versatile, it is often purchased by contract packagers who never know what their next filling challenge is going to be. Examples of the range of products that can be run on this machine include soaps, pharmaceutical products, oils and greases, cosmetics, salsa and sauces, etc. etc.

The challenges of this machine are its high capital cost and the ability of the owner to conduct normal maintenance on a more sophisticated machine. Positive displacement pumps are expensive and so are servo controlled drive systems. Troubleshooting and maintenance requires reasonably competent technical level. However, if affordable, this type of filler is an outstanding choice for nearly any type of filling operation.

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Peristaltic liquid filler
This filler is the machine of choice for high value, small volume fills at very high accuracy. It is primarily suitable for aqueous and other light viscosity products. Examples of products filled on this machine are sterile and pharmaceutical preparations, fragrances, essential oils, reagents, inks, dyes, and specialty chemicals. The unique advantage of this machine is that the only fluid path is surgical tubing. The fluid path is disposable; easy to cleanup and eliminates cross contamination problems. Accuracies of 0.5% are achievable for fill volumes less than 1 ml.

The peristaltic pumps on this filling machine make intermittent contact on only the outside of the surgical (product) tubing so that the product only touches the inside of the tubing. Like the servo pump filling machine above, this system operates with servo drives. Each servo drive is dedicated to one or two peristaltic pump heads. The filler's master computer independently tracks the # of rotations of the peristaltic pump head so that it knows precisely how much product has been delivered. When the target fill volume is reached, the pump stops and the remaining product fluid does not drip out due to pipette action of the surgical tubing.

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Time Gravity liquid filler
This is the most economical type of filling machine for a limited range of applications. This filler is best suited for liquids with very thin viscosities that do not change with ambient temperature or with batch variation. This machine is also suited for applications where recirculation of the liquid in the fluid path is not desirable. This is especially true for corrosive chemical filling like acids and bleach. Other examples of products this machine is well suited to include water, solvents, alcohol, specialty chemicals, paint and inks. Although this type of filler is used predominantly on products that do not foam, foam may be limited and controlled by subsurface/bottom-up-fill capability.

The machine works by a simple principle; the amount of liquid flowing through a fluid path will always be the same for a fixed amount of time. It functions as follows: the product bulk supply is pumped into a holding tank above a set of pneumatically operated valves. Each valve is independently timed by the filler's master computer so that precise amounts of liquid will flow by gravity into the container. Independent timing of each filling valve/nozzle corrects for minor variations in flow rates so that each container is filled accurately.

The disadvantage of this type of technology is that the dynamics of the fluid path and nozzle actuation characteristics continuously change over time. This requires the operator to make adjustments to the machine's stored parameters more frequently than other technologies. Notwithstanding this drawback and the limitation of the range of products that can run on this filler, it offers excellent value for its performance.

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Piston liquid filler
The piston filler is one of the oldest and most reliable types of fillers used in the packaging industry. This filling machine is best suited for viscous products that are paste, semi paste, or chunky with large particulates. Piston fillers are primarily built to meet food grade standards and commonly fill heavy sauces, salsas, salad dressings, cosmetic creams, heavy shampoo, gels, and conditioners. Thy are also used for viscous chemical preparations like paste cleaners and waxes, adhesives and epoxys, heavy lubricant oils and greases.

The machine works by a simple principle; The piston is drawn back in its cylinder so that the product is sucked into the cylinder. A rotary valve then changes position so that the product is then pushed out of the nozzle instead of back into the hopper. The volume of the product that is sucked into the cylinder is the precise volume that will be dispensed into the container.

The advantage of this type of filing machine is that involves conventional mechanical technology that is easy to understand for most users. It is also the most cost effective, accurate and fastest way to fill fairly thick products. Although more costly than overflow and time gravity systems discussed above, it costs less than the servo pump filler is still the most cost effective filling machine for thick products.

There are several disadvantages this type of filler. It is practically speaking, NOT suitable for thin products because the mechanical characteristics and clearances of the machine parts allow for leaks on thin products that do not occur on thicker products. The other major disadvantage of this machine is that if there are multiple product and container size changes involved, the cleanup and "tweaking" processes are tedious and time consuming. Lastly, there is a finite range of fill volumes per piston set that can be run on the machine. An operator who needs to fill both gallon containers as well as 8 oz containers will find they cannot run the 8 oz containers accurately using gallon or half gallon piston sets. (This is where the servo pump filler is superior)

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Net Weigh liquid filler
This type of filler is best suited for liquids filled in bulk quantities e.g. 5 gallon pails, etc. or smaller quantity products that have a very high manufactured value. Oftentimes there are products that must be sold by weight for commercial reasons and therefore this filling machine is the only choice. Examples of this type of filler for bulk products include cleaning chemicals, enzyme solutions, oils and other medium value products. High value products filled by these machines include specialty adhesives and paints, precious metals dissolved in acids, and other expensive specialty chemicals.

The operation of this type of filling machine is simple. The product bulk supply is pumped into a holding tank above a pneumatically operated valve. The valve opens and real time net weight information is monitored until the target weight is achieved. The valve simply shuts when the target weight is achieved. Accuracy of fills is accomplished by various "bulk and dribble" methods in the filling process so that overfills are avoided.

The advantage of this filling machine over others is that it is sometimes the only practical (and legal) type of filling for a limited range of applications and for large volume fills. It is also very accurate and effectively provides its own quality control assuming the scale is functioning properly. The disadvantage of this type of filling machine is that it is very expensive per filling head and it is also a relatively slow method of filling into a container. For these reasons, the use of this filling technology is limited to the examples outlined above.

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Hazardous Location liquid filler
Any of the machines outlined above can be built for Hazardous Location operation. Hazardous location means that there is risk of explosion or auto-ignition of the products being filled. Examples of products like this are alcohol, solvents, petroleum products, paints, etc.

Many of the manual and semi automatic versions of the types of a liquid filler discussed above are inherently safe since they require no electrical operating systems. However, more sophisticated and higher output automatic machines using electrical systems must be built with intrinsically safe enclosures that are UL listed and conform to the National Electric Code as well as requirements of major insurance carriers.

There are automatic a liquid filler offered in the market with completely pneumatically controlled operating systems. However, the major disadvantage of these systems include susceptibility to inconsistencies of plant air volume and pressure. In other words, there is risk that pneumatic logic controlled machines will not function repeatably. For this reason, hazardous location a liquid filler using electrically safe systems are prefereable because they can offer all the consistency, convenience, and efficiency of conventional fillers including full visual displays and user friendly controls.

The disadvantage of this type of system is high capital cost but oftentimes, there is no choice in the matter.

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Corrosive Environment liquid filler
As suggested above, time gravity fillers are often used for filling of corrosive products. But sometimes the products being filled are so aggressive that special construction methods are required. Harsh factory environments or where the product being filled can also be particularly aggressive on machinery. This includes not only chemical plants plants producing strong acids or bleach but also food plants using brine or sugar solutions in their products. In both cases, even the factory air alone contributes to the accelerated degradation of the machinery.

Machine integrity can be enhanced by using special powder and industrial polymer coatings on structural and other exposed machinery components. Also, whenever practical, substitution of chemical resistant plastics such as UHMW and Teflon are used in place of metal.

Not only are the frame components at risk in these environments but the fluid path materials must be specifically chosen for the types of products they come into direct contact with. For example, Kynar and Teflon fluid path materials may be used in a bleach filling machine because of their excellent resistance to the aggressive properties of bleach.

It should be noted that there is no ideal combination of materials in a filling machine when it comes to corrosive filling. Avoidance of some metal components is impossible particularly in the case of fasteners. The operator of this type of machinery should be prepared for stringent maintenance of these types of machines.

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