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Tablet Dedusting: Which Method Fits Your Process?

Source: Kraemer US LLC

Weighing The Pros And Cons Of Horizontal, Vertical, And Brush-Type Dedusters

By Andre Petric, President, Kraemer USA

There are a number of things to consider when integrating a deduster into your manufacturing line. Before contacting a supplier, be sure to assess your needs by gathering the following four pieces of data:

  1. Identify your minimum and maximum tablet sizes. The size of the tablets, along with the speed at which tablets enter the deduster, determines the volume needed on the helix to effectively transport and dedust.
  2. Know the maximum speed related to running all sizes of tablets.  This information allows the provider to determine the deduster capacity, so the appropriate machine size can be recommended.
  3. Determine if you need a metal detector along with the deduster. A metal detector uses roughly 10” of vertical height, which must be accounted for in the machine height calculation.
  4. Assess the press outlet height and collection container inlet height. You can figure this by measuring the vertical distance from the floor to the table outlet chute at the press, and the tablet collection container height. These two dimensions will allow you to calculate the deduster conveying height — the vertical height needed to properly reach the collection container.


Once you’ve collected the above data, it’s also important to familiarize yourself with the types of dedusting methods available. Horizontal, vertical, and brush-type dedusters all come with their own challenges and advantages that should be analyzed before making your choice.

Horizontal, Vertical, Or Brush Type: What’s The Difference?

Horizontal Dedusters: Horizontal dedusters consist of a perforated stainless-steel plate that vibrates side to side, and the tablets basically fall from the press to that plate. The plate isn’t actually horizontal — it has a slight slope — so the tablets slide down as they are moving with the vibration for about a meter in length.

The biggest “pro” for a horizontal deduster is that it is inexpensive. However, choosing to buy a deduster based on price point is not always the right decision. You might save on cost up front, but horizontal dedusters do come with the following “cons” that could impact your facility:

  • The noise level is high.
  • The amount of time that the tablets are on the above mentioned plate isn’t very long. The purpose of the plate is to dislodge the dust from the tablets, and since the residence time is short, it is not a very efficient dedusting method.
  • They have a rather big footprint, taking up room inside the press area or the press suite that may not be available. 
  •  Only small tablet collection containers — two feet high or less — can be used with a horizontal system. Press outlets typically are about three feet or so off of the ground, so by the time you have a horizontal deduster, along with a metal detector, you are almost at floor level. This limits the size of the tablet container that can be used and can pose ergonomic issues for the operators from the repetitive bending and lifting of quickly filled small containers.

Vertical Dedusters: There are two different types of vertical dedusters to consider:

  • Vertical downward conveying deduster: This is an older style of deduster which is very similar to the horizontal type. The tablets enter at the top, go down through a number of flat perforated plates, and then bounce around until they find the exit to drop to the plate below. They pass from plate to plate until they drop out of the bottom of the machine. This type of deduster is relatively inexpensive. However, the downsides are comparable to the horizontal deduster, in that you do not have a lot of vertical height for tablet collection and metal detection, and they are also very noisy.
  • Vertical upward conveying deduster: This particular deduster utilizes a helically wound tray around a center column. The tray is sloped upward and allows the tablets to convey upward by vibration. A positive aspect is that it has a very small footprint. By conveying on this upward spiral, it allows for a very long residence time (the amount of time the tablets are being dedusted)— the shortest being five meters — in comparison to the horizontal type, which is one meter. This is important because the longer the residence time, the better the dedusting efficiency. In addition, when tall containers are needed, the spiral helix can be equally as tall. In fact, some can go up to 20 meters of residence time, which allows for the tablets to be raised up from the press and to be dropped into much larger containers, like drums. Since the trend in the industry is to make bigger batches at faster press speeds, it’s important to be able to use larger containers.
  • The cons are that vertical conveying dedusters have a higher initial cost, and could require more initial set-up as there are more than one parameter for proper operation.

Brush-Type Dedusters: Brush-type dedusters consist of a helically wound brush located inside a stainless steel tube, driven by a motor. The tablets enter from the side of the tube, and the brush turns and vertically raises the tablets up the tube, until they reach the exit at the top of the unit. Two upsides to this method are its inexpensive up-front costs, and vertical conveying, which is not possible with horizontal type. On the downside, it uses plastic brushes, which can statically charge a product. And, the brushes can wear, which poses the problem of where those worn particles and broken brush fibers are going. Some of the particles exit with the dust, and some stay with the tablets, which is a definite negative. The brushes also can be difficult to clean. Like the horizontal method, the residence time is rather short — up to a couple of meters.

Before considering brush-type conveyors, it’s important to note that they are generally a better solution for conveying capsules. Manufacturers like to see their capsules polished and shiny when they come out of the system. Brush type, because of the friction of the brush on the capsule, is a good solution for that.

You Have The Information, Now What Should Drive Your Decision?

Aside from cost, the deduster decision should be based on dedusting efficiency and the physical ability to have larger containers in place. With the industry trend towards larger batch sizes and continuous manufacturing, the ability to collect a large volume of tablets is important. If, for example, your press tablet chute is at the height of 36 inches and your drum is 36 inches — if you didn’t have a deduster or a metal detector — you could put the drum right next to the press. However, with the horizontal deduster, you need to dedust and metal detect, so you’re dropping through the deduster roughly 8 to 10 inches. Add the metal detector, and you are dropping 10 or more additional inches. As mentioned earlier, this limits the size of the container that can be used. With a vertical conveying deduster you can go upwards from those 36 inches, in increments of about 10 inches, and then drop through the metal detector. The tablets can be discharged into large containers, even higher than the press outlet height. Many manufacturers use stainless steel and plastic IBCs (intermediate bulk containers), as well as flexible IBCs, so that they don’t have large quantities of small tablet collection containers to handle, store, and track. By minimizing the number of tablet collection containers, it makes those tasks much easier.

Tablet deduster choices are numerous, but with the information outlined above you will have the knowledge to make an informed decision.