Air jets give less impact than an air nozzle but have the advantage of hitting a broader target area. This makes them suitable for some air blow-off applications where a medium impact is required over a relatively small target area.
Air nozzles are designed to produce very focused “spot” jets of air force. Air jets, on the other hand, produce a slightly broader spread of air but with reduced impact. So, when an area needs blow off, consideration needs to be given to how far apart the individual nozzles will be. The data sheets will show the approximate patterns and spread of the air flows from different nozzles at various pressures and distances. This will help determine positioning. Also the distance from the target will, like as with air knives, ultimately determine the blow-off force seen by the target.
One potentially big advantage of compressed air blow off systems over powered blowers is that they are able to be cycled off and on very quickly. This means that the air blow off only needs be delivered when it is needed. Obviously, this is no advantage when continual blow off is required but with many conveyor based systems the blow off is only require periodically as product passes. Connected to a simple solenoid valve system an air nozzle system can be switched on just as product passes. This can save a considerable amount of energy.
When compared to blower systems enhanced compressed are blow off systems are very easy to maintain. Whether the system is comprised of air nozzles, air knives, air jets or air edgers 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.
All the compressed air enhancement nozzles used for air blow off systems work under the same basic operating principles. Compressed air enters the nozzle and is shaped into an outlet pattern of increased velocity air flow. Additional air inlet holes allow the surrounding air to be drawn into the nozzle and/or the external shape of the nozzle encourages further air entrainment by the Coanda effect. The result is a significant amplification of the amount of air moved.
Whilst the various types of air nozzles do operate under the same principles they produce very different effects in terms of blow off area and force. Understanding these differences is important when working out which is the best product for a specific situation
Air knives (long line pattern with high impact) – Will produce high impact air force concentrated in a line along the length of the knife. As the pattern is linear if a surface needs to be treated the some sort of relative motion needs to be introduced. The most common method for this is to deploy the air knives on a conveyor so the product passes through the line of air.
Air edgers (short line pattern very high impact) – These produce a very high impact air force over a short length. They operate like short by highly focused versions of air knives.
Air Jets – (circular pattern with medium impact) – These nozzles produce a focused relatively high impact jet. Looking face onto the nozzle it would produce a circular air current. The air jet sits somewhere between the very focused air nozzle and the less focused air amplifier. It is a good choice of product for spot blow off systems that require a reasonable amount of impact.
Air Nozzles – (narrow circular pattern with high impact)- These nozzle are shaped to produce a single jet or stream of air. They are engineered to ensure the resulting air flow remains laminar as long as possible. They are best deployed when precise high impact jets are needed to hit a spot or point for blow-off.
Ring blade – These are essentially air knives that have been bent around to form a circle. The air force is directed inwards and so are used on extrusions and other tubular shaped product lines when can pass through