Tablets & Capsules


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Tablets & Capsules April 2018 17 A they were sidetracked by improperly functioning flow systems. To circumvent this lack of knowledge about flow-meter function, many companies opt to run their flow meters in mass mode, claiming that their tablets are coated using the weight-gain method, so flowrate isn't critical. This statement could not be further from the truth and is not a valid justification. For example, if you have your flow meter operating in mass mode but haven't re-zeroed the meter recently, the system may not actually be delivering the desired flowrate. This will impact the solution's atomization, spray pattern, and droplet size, all of which directly affect tablet appearance. Excess flow can cause over-wetting of the tablets, which contributes to problems such as twinning, picking, sticking, and erosion. Some of this excess solution goes directly to the dust collector, which creates buildup in the ductwork, prematurely blinds the dust collector filters, and increases downtime and maintenance costs due to more frequent ductwork cleaning and filter and waste drum changes. Also, to make up for the wasted solution, you may need to increase the coating solution batch size by 20 to 40 percent to avoid running out of solution before the tablets reach the desired weight. If your actual flowrate is lower than the desired flowrate, on the other hand, the solution may atomize too quickly, and the droplets will dry before reaching the tablets. The solution droplets must contain enough moisture at the time of impact to adhere to the tablet surface, otherwise the dry particles will bounce off the tablets and be carried away in the exhaust airstream to the dust collector. This also wastes coating solution. Both of these scenarios are preventable if you understand how your equipment operates. Volumetric flowrate is a more appropriate form of measurement than The single-tube Coriolis flow meter is a critical but often misunderstood component of pharmaceutical tablet coating systems. This article provides tips for setting up and maintaining your tablet coater's flow meter and coating solution delivery system to help ensure accurate flowrate measurements and optimal coating solution delivery. single-tube Coriolis flow meter is a cylindrical device that's mounted inline on a tablet coating system's solution supply tube. The flow meter monitors the coating solution flowrate and directly or indirectly sends the data to the coating pump controller, which continuously adjusts the pump speed (rpm) to maintain the required flowrate. As coating solution flows through the meter, it generates friction, which causes the tube inside the flow meter to vibrate and twist. This vibration varies in frequency depending on the speed of the solution f l o w i n g t h r o u g h t h e m e t e r a n d t h e s o l u t i o n ' s characteristics. A sensor inside the meter measures this frequency and uses the measurement to calculate the solution's flowrate, either by converting density to a mass flowrate or by using multiple variables such as temperature, pressure, viscosity, density, and percentage of solids to calculate a volumetric flowrate. I have yet to work with a process engineer, develop- ment scientist, or technician who truly understands the function of a single-tube Coriolis flow meter well enough to troubleshoot flow system issues. This knowledge gap often leads to poorly validated flow systems that technicians and operators are left to deal with on a daily basis. I often wonder how many unrelated mistakes frustrated technicians or operators have made because Optimizing coating solution delivery system and single-tube Coriolis flow meter performance Bill Maschinot Independent consultant tablet coating

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