Air Knives for Drying

Air knives produce high impact air streams along their entire length. The high force produced by these product means that they are a suitable choice of product for air blow off / wipe drying applications.

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The process of blasting water from a target that needs to be dried is distinct from the process of evaporative drying. With a blow off drying action the force of the air, rather than its water absorption properties, are used to drive the water from the target. Of course, evaporation also takes place as a secondary drying process as well.

As the objective of the exercise is to drive water from the target success depends on the air force being applied. Rapidly moving, focused air currents will help blast water from the surface being targeted. In general, the higher the impact (velocity) of the air the more rapidly the object will be dried. This is particularly true if the target is odd shaped like a bottle. Due to the shape of the bottle, regardless of which side the drying air blast is coming from some of the surface will be shielded from the initial blast. Air will tend to move around the entire object but this will be at a greatly diminished velocity when compared to its initial contact point. So, if we can maximise the initial contact velocity we can preserve enough air impact to deliver effective water blow off to the shielded parts of the target surface.

The need for high impact air force means that air-edgers, air knives and air jets are the most commonly used products.

Air edgers are a good choice when maximum impact is required. For example, the product is very wet or moving rapidly on a conveyor OR when the object has a complex surface and so parts are shielded from the initial air contact.

Ring blades are and excellent choice for any object that can travel through the internal diameter. They deliver 360 degree high impact air flows and so will target the object being dried from all angles. The obvious limitation of the air blades is that they have a maximum size of about 11” diameter and so are not suitable for large objects.

Air knives deliver high impact and very focused linear streams of air. Air knives can be made in lengths up to 54” (1371mm) and can also be daisy chained together to form even longer lengths. Air knives are a perfect water blow off solution for conveyor systems.

Maintenance and reliability

When compared to blower systems enhanced compressed are drying systems are very easy to maintain. Whether the system is comprised of air nozzles, air amplifiers, air jets or air knives there are no moving parts involved and no external power is required. This means that there is virtually nothing to go wrong with the blow off system.

The simplicity of these systems means they can be deployed in areas that would preclude the deployment of powered blowers. In dirty, wet or humid areas of the production facility any powered equipment requires often costly protection to prevent it breaking down. This may involve water proofing or additional filtration / dust protection. Compressed air systems require none of this and so, in such environments, they are intrinsically more reliable.

Noise Levels

Noise is a constant hazard when using air systems. Both blowers and compressed air blow off systems can be very noisy and constant exposure to high noise levels is a big health and safety concern. Indeed, there is stringent legislation in many countries that limit workers exposure to certain noise levels in the work place. As such noise reduction is often a critical design factor in air blow off applications.

Standard air knives will typical reduce noise by 10 dBA when compared to open air hoses at the same pressure. Typical noise levels will be in the region of 69-75 dBA for most applications.

Silent x-stream air knives are more efficient meaning that they can produce similar impact with less air and less feed pressure. This means noise can be reduced further because, ultimately, the noise level is determined by the input air pressure.