By Matthew Forknall

The littlest things can damage a conveyor and stop production, whether filling five bottles of water per day or 50,000. Tiny droplets of water are a case in point: they’re everywhere on a conveyor system in a bottling plant and come from a variety of sources. They make it difficult to attach sleeve labels, impossible to code bottles with an inkjet and can even represent a contamination risk. The key to avoiding headaches from excess water is a drying apparatus on the conveyor line, a focused blast of air from any number of unique systems such as wind jets, air knives and plate dryers.

Causes of dampness
Let’s begin by outlining those points on a conveyor system where water or other liquid is most likely to become a problem and the damage it could cause. Numerous factors can create a significant amount of excess water on during the manufacturing process, including:

  • Lubrication. Most conveyors are wet-lubricated to keep their many parts running smoothly. This lubrication can splatter onto product bottles and interfere with label adhesion or the conveyor process itself.
  • Bottle washing. The simple act of cleaning a returned five-gallon bottle can make the product too wet to handle without special care.
  • Condensation. Cold water pouring into a room temperature bottle will create condensation on the outside. When it builds up, this liquid can ruin packaging and make attaching labels a nightmare.

Wet surfaces make sleeve labeling difficult or impossible, inhibit the ability to apply a safety seal and compromise the hygiene of the system. After production, this excess water can also damage cardboard packaging and make it impossible to effectively shrink-wrap a package or even pallet.

Drying: how and where to dry
The most common method for drying excess liquid on a conveyor system is with moving air. Sounds simple enough, but there are a host of different options out there and it’s important for a bottler to understand the differences between them.

One of the most common practices for drying bottles is a compressed air system. Compressed air nozzles, also known as wind jets, deliver blasts of air continuously over filled bottles as they pass on the conveyor, using technology similar to that of the compressors system used to fill automobile tires. However, they are notoriously loud and consume an enormous amount of energy and money.

Another technology, called an air knife, is similar to wind jet nozzles, but provides air through a blower-driven system. The unit consists of a plenum chamber with a smooth convergent path to a controlled exit slot. Think of putting your thumb over the end of a garden hose to get a higher-pressure stream of water while washing your car, the ratio between the exit slot area and the blower discharge area is sized to give a reasonable backpressure along the length of the air knife. This ensures an even distribution along the knife providing relatively uniform exit velocity. Air is supplied to this plenum chamber using a blower, capable of generating flows that are typically in excess of 150 cubic-feet per minute. This process makes air knives far more efficient, less noisy and more compact.

Types of air knives
Air knives are typically constructed from aluminum alloys and fabricated or welded stainless steel and these units can be adapted to an existing conveyor system in several ways. An Open System is typically the lowest cost solution with the blower sited remotely and ducting or flexible hose attached to an air knife at the conveyor in an open spot after filling. Floating Open Systems reduce the footprint by situating the blower above the line in its own enclosure and help to significantly reduce noise levels. They also can be easily repositioned. Finally, a Closed System employs a fully enclosed drying chamber to nearly eliminate noise and reduce the risk of water transfer; however, it requires a larger footprint.

New drying techniques
At the forefront of bottle-drying technology is a new, air knife-based system known as a plate dryer. These plate systems are similar to air knives in that they utilize blowers instead of compressed air; but instead of a single, directable exit slot positioned above the conveyor, the unit is the length of about a dozen bottles and blows them as they pass. Acting as both a dryer and a guide rail, a plate dryer system directs air downward along each side of the bottle, preventing water from spraying onto other bottles and protecting the conveyor itself. As the bottle travels along inside the system, the exit slots step downward so excess water is pushed further and further down the bottle and eventually away from it. This allows the exit slot to be incredibly close to the bottle without interrupting its travel along the guide rail and, simultaneously improves the drying performance.

When considering the addition of a drying system to your bottled water manufacturing plant, or five-gallon washing and refilling operation, it is important to remember the bottle size, production speed, conveyor specifications and maintenance costs are all important factors in the selection process. Not all air dryers are created equal, but even if they were, no two bottling plants are built or operated the same way.
Whether it is air from a wind jet, air knife or plate dryer, the goal is both to dry the bottle before it is packaged, and to keep that excess liquid from damaging other parts of the system or inhibiting other bottles down the production line.

About the author
Mathew Forknall is Marketing Director for Air Control Industries Ltd., a United Kingdom-based manufacturer of industrial fans, blowers, air knife systems and plate dryers for surface drying, cooling and static neutralization. Their newest plate dryer system JetPlate, is a revolutionary product, effective for high-speed lines with cold bottles where surface dampness affects the ability to attach labels, assign barcodes or other imprints directly on the bottle and package the product after filling. For more information about ACI, visit or email the company at [email protected].


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