Controlled vibrations for optimal product flow

Many pharmaceutical powders are cohesive and do not flow consistently out of the supply hopper during feeding. Examples of such poor flowing materials can include excipients such as micronized lactose, magnesium stearate and various active pharmaceutical ingredients or API’s. Such poor flow properties can lead to the formation of rat holes or even material bridges, making it difficult to accurately deliver these materials to the process. This is especially of importance when feeding to continuous processes such as continuous direct compression, granulation, extrusion or coating. The Coperion K-Tron ActiFlow™ Bulk Solid Activator is the perfect solution to avoid this problem. This technology ensures maximum possible optimization of material flow, is easy to clean and has no effect on  the material properties.

Poorly flowing bulk material can impact feeding
A rat hole is a narrow, vertically oriented tunnel from the top of the material bed in the hopper to the discharge device of the feeder. Although material can continue to flow through these holes, the discharge rate of the feeder is considerably lower and material deposits may remain in the hopper for an indefinite amount of time. Material bridges similarly restrict the flow of material through the feeder. These material bridges can lack even the vertical tunnel of  a rat hole, causing the material flow to be completely blocked.

A traditional method of coping with these problems is to install a vertical agitator in the feeder hopper. On the one hand, this solution is very reliable but on the other, it also has several disadvantages such as significant cleaning effort and additional headroom. In addition, due to the pulsations caused by the vertical agitator,  fluctuations during feeding cannot be ruled out.

Controlled vibration keeps the material moving
Coperion K-Tron’s unique ActiFlow Bulk Solid Activator reliably prevents the formation of bridges with even the most poorly flowing materials. It essentially consists of the ActiFlow device attached to the outside of the stainless steel hopper and the ActiFlow control module which closely interacts with the KCM feeder control module. The ActiFlow device gently activates the material in the hopper with an optimized amplitude and frequency, while the KCM in combination with the ActiFlow control module ensures that there is always an optimal material flow in the hopper. This in turn provides for consistent and highly accurate feeding.

How ActiFlow outrivals vertical agitators
The advantages of ActiFlow over traditional vertical agitators are not only time savings and cost reduction but also improved end product quality. The device is completely non-product-contact which eliminates cleaning and hygiene concerns. With a vertical agitator, there is still material left in the hopper after running empty. Customers report that cleaning is likewise much easier with the ActiFlow. Whereas the vertical agitator is laboriously removed for cleaning and therefore requires additional headroom above the hopper, there is no extra headroom required for the ActiFlow device that stays mounted on the feeder hopper. With some products, the maximum discharge of the feeder can be significantly higher than with a vertical agitator. This can allow the line output to be increased, sometimes by as much as 50%. In addition, there are fewer interruptions, for example with poorly flowing products. The bulk material is neither compacted nor mechanically overstressed.

In the set-up shown here, the ActiFlow device is attached to the rear of the hopper. The red arrow shows the direction of hopper activation. The position and direction of activation have been optimized during extensive feeder trials in the laboratory in order to minimize their effect on the weighing system and at the same time maximize the flow of bulk material.

Vibration-immune weighing
The filter algorithms in the feeder’s weighing system effectively filter out vibrations, thus ensuring an exact weight signal at all times – even when the ActiFlow’s activation of the bulk material is at maximum.

Act instead of react
The most important concept underlying the ActiFlow system is to act instead of react. This is especially important when differentiating it from traditional vibrators or "knockers" which may simply be placed on the outside of the hopper. The feeder control module has the ability to recognize deteriorating material flow in the hopper before a possible mass flow error occurs. In this situation, the ActiFlow increases the amount of vibration applied to the hopper wall, activates the bulk material flow and prevents feedrate errors. In addition, the real time agitation control prevents additional packing of the material in the hopper which is often an issue with traditional external vibration methods.

As soon as the control module detects normal material flow, the ActiFlow reduces the activation of the material again. The control system and weigh module are using actual real-time performance data to activate and control the level of vibration. Owing to a specially developed patent-pending control algorithm the ActiFlow only activates the material in the hopper as much as necessary and not as much as possible. A sensor integrated into the ActiFlow is an additional distinctive feature that functions as a positioning feedback device for the control module. The activation amplitude and frequency can thus be monitored and regulated precisely.

Equipment start-up
Once the equipment is securely installed, two steps are necessary for commissioning. To ensure that the ActiFlow runs reliably and uses energy efficiently, the resonant frequency of the entire system has to be determined. The hopper should be filled with material up to the upper limit. When the feeder is started up, a short frequency search is performed and the resonant frequency that is found is saved. In addition, a material flow property that only has to be estimated once (easy, medium or hard) must be defined in the feeder’s KCM control module. This setting specifies a lower limit for the ActiFlow’s activation of the material in the hopper. Once the equipment is operating, no further inputs are necessary; from this point on, the ActiFlow self-adjusts. If the feed material is changed, both commissioning steps must be repeated.

Successful applications
Having been on the market for over a decade, the ActiFlow Bulk Solid Activator has proven its efficiency in many installations and in many different pharmaceutical processing applications around the world.

ActiFlow can be used with all Coperion K-Tron LIW modular feeders equipped with a Coperion K-Tron Control Module (KCM) and standard 4D and 6D asymmetric hoppers, up to 180 dm³ (6.4 ft³).