So when we look at the claims made by blower & airknife manufactures (low pressure). Their claims are much more realistic! In most cases you can replace compressed air powered airknives with blower powered versions. And this can be done at a significant cost saving. In many cases up to 80% reduction in the cost for the power to drive the airknives. In these cases you could see a payback on the capital cost of the blower powered systems in as little as 3-4 months! And you continue to reap the cost saving for many years to come. What they fail to mention and recognize is that in some case, not many, compressed air may be the best alternative!
Here is why;
Line size – they can be powered by a ¼”, 3/8” or even a ½” line size. Blowers will require from a 1”up to in some case 6” line sizes. Once you go past the 4” line size requirement you will be dealing with custom designed airknives specific to your environment and requirements.
Control – Compressed air is much easier to automate which allows you to integrate optical eyes and only blow air when a part is in the airknife section. If you can justify the cost to add the controls to a line this could be a low cost alternative. This would be a case if you are only blowing air say 25% of the time or less. Because compressed air can be stored you typically are operating from the reservoir tank. Blowers do not allow for this and they must keep air moving through them for proper cooling. If blowers do not have enough air passing through them for cooling you will shorten the bearing life.
They also claim that compressed air is “dirty air”. They are referring to the fact that plant air compressors are typically oil lubricated and must incorporate expensive oil mist coalescing filters on the discharge. If this filter is not properly maintained and changed regularly you will have oil migrate past the filter and work its way through the entire air stream passing through the airknife and onto the product being airknifed. Should this be metal that needs to be painted you will now end up with “fish eyes” in your paint.
Along with oil in the airstream we cannot forget about condensation! This is a known as we have some moisture saturated into the air we breathe every day. As we know, a small amount or low relative humidity is great you still must be able to handle the high humidity days. (This will be addressed again on a future drying blog). When you compress saturated air the moisture in the air condenses out and becomes water. Except now it is worse! Remember that there is also oil in the air. They do not mix but they both carry through an air system. Condensation is dealt with at many locations through your compressed air system. From the compressor reservoir all the way to the compressed air line drops. At the end of each drop you would find a FRL or just an FR unit (filter, regulator & lubricator) pending on if you are using air tools which require lubrication. The airknife drop should only have the filter / regulator.
So as you can see we have pointed out some the pros and cons of each system. When looking at an airknife system it is best to understand all options that are available to you and look at the total operating cost for the future.