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Comparison of HVLP (Blower supported) Air Knife Drying system with other systems. |
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With high speed automated production lines, washing, cleaning, cooling, quenching, rinsing with liquid and many such in line processes have become essential.
Most of these processes will leave liquid (mainly water based solutions) on to product.
In most cases this residual liquid needs to be dried or removed from the product to facilitate ink jet coding, printing, packing, cooling etc.
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There are many different methods to help drying/removing liquid from product. Most popular being : |
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a) Mechanical wiping with squeeze rolls or sponge or cloth.
b) HVLP Air Knife System.
c) Compressed Air, Air Knife System.
d) Thermal Drying. |
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In most cases Mechanical wiping or Forced Air drying do not yield complete and effective drying.
Other three processes in most cases can give desired results. Hence attempt is being made to compare these three systems, its advantages and disadvantages, capital cost and energy cost comparison and other considerations.
Some factors in comparison are indicative only and data may change for different parameters of applications.
Reader may use this comparison as guidelines and draw their own conclusions to decide the system best suited for their application. |
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Comparison of HVLP (Blower supported) Air Knife Drying system with other systems. |
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Blowers
Some designs of HVLP Air Knife Systems use CENTRI FUGAL BLOWERS. Normally CENTRI FUGAL BLOWERS are meant for high volume and very low pressure air deliveries.
However, in order to get higher pressures these blowers are run at very high speeds. Normally in between 10,000 rpm to 15,000 rpm, but sometimes as high as 24,000 rpm.
Such high speeds requires special type of costly bearings, precisely done dynamic balancing of rotating components such as impeller, pulley etc
Also in order to ensure proper speed special types of belts (similar to timing belt) are used.
To ensure proper trouble free running, Blowers will have to be mounted and leveled precisely and anchored.
Special grease/oil to suit high rotating speeds need to be used.
If such cares are not taken, bearings and belts heat up and wear out very fast, requiring costly replacements and costly and time consuming downtimes.
See following illustration for easy understanding. |
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Air Knife
Air Knife profile should be designed to create least turbulence and provide
Uninterrupted and controlled laminar flow. This stability will guarantee minimum surrounding air excitation on downstream leg and narrow pattern on the up stream end. This also ensures maximum efficiency at reduced pressures and therefore reduced energy costs.
Air knife profile should be sturdy and treated to withstand working conditions.
In many Air Knife designs some of these features are not provided. |
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Mountings
It is most important to design mountings, which gives maximum flexibility to be able to mount in most difficult locations.
It is equally important to be able to adjust Air Knife on location so that Air Flow is precisely directed at the surface to be cleaned/dried/cooled.
Also these mountings needs to be sturdy and made from materials, such as S.S. so as to withstand working conditions.
Unfortunately some manufacturers do not look after all of these needs, creating situations, where the user has to do with lot of improvising or make do with lesser efficiency, more maintenance etc. |
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| Some of Air Knife Applications |
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