Let’s start with a little truth in advertising. Here are the claims made by manufactures the two major types of airknives: (compressed air powered & low pressure air / blower powered).
Compressed air people say they are the only efficient airknife on the market because of the following statements:
- You already have the compressor
- There air is amplified by atmospheric air adding to the known discharge CFM by a factor of up to 20X
- Does not require filter or belt replacements
- Does not require replacement of expensive air ends cost up to $4,000 every 2-3 years!
These are all an attempt to mislead you into thinking that they are the lowest cost way of getting into and operating an airknife system. Though these are true statements let’s look at each one!
So you have a compressor! Do you have plenty of excess compressor capacity? I am sure every company has more air available than they know what to do with. Here is the rule of thumb – 1” of compressed airknife consumes 4 cfm @ 80 – 125 PSI. Even if you can dry your part at 80 PSI, you paid to compress your air to 125 PSI. That was not free!
Air is amplified: wow, there is a statement. It’s pretty hard to measure that. Of course it is amplified. Have you looked at the new “bladeless” fans where air is discharged from what is basically a gap that is on the outer edge of the fan circle. (Think airknife). This occurs with all air that discharges from a higher pressure to a lower pressure (atmosphere, in this case). Even the lower pressure blower powered airknives operate with the same principle. One thing to note, some shapes work better which will be addressed in future blogs.
Maintenance: this is the real joke! Of course a compressed air airknife does not require maintenance but they are now comparing only their airknife and not the source of the air that powers it! Again, this is a misleading statement. Being an election year you can probably catch this one yourself. I have seen them claim anywhere from $500.00 and up per year for belts and filters required by some of the manufacturers of both the blowers and airknives. True these belts and filter need to be serviced, but so do the belts and filters on a plant air compressor. But the companies making these style airknives DO NOT MANUFACTURE THE COMPRESSOR! Do you know the average cost to maintain a plant air compressor is about $90.00+ / HP / YR!
Replacement of blower air ends: yes this is required. With today’s technologies companies have developed some great ceramic bearing. The blower manufactures utilizing this technology will tell you to expect 20,000 hours of service. This is pretty accurate. However 1 shift per day times 52 and you are looking at 2,080 per year. If you are running 24/7/365 you are looking at 8,736 hours. So how come many users of these blowers do not get the full life expectancy from the blowers?
Here are some factors that you need to add to the equation:
- Operating environment – temp, air quality, filter quality
- Belt drives like it dry; make sure you do not have liquids in the area while operating
- Wash down area / chemicals
- Sugars in the air – this is a real issue in beverage plants
- Location of the blower to extreme environments
- Where and how a blower is mounted to a piece of equipment
If you are a steel mill and utilize anything but a robust blower you are asking for trouble.
So looking at the combination of the above mentioned problems you can understand why you may not be getting the hours of service you were expecting. But here is the icing on the cake, every couple of years the salesman has to tell you how great his product is so you can buy a new or remanufactured air end to the tune of about $3,500 & up pending size / model. Yes, you may have figured it out. These manufactures have created a very expensive razor blade. Keep in mind that these blowers could be the BEST option for your application and it truly is a cost of doing business. The biggest advantage of the high speed centrifugal blowers is their compact size. You get a lot of air out of a very compact blower. The cost of doing this is a costly blower to maintain.