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34 July 2020 Tablets & Capsules put to allow for process monitoring, including signal-to-noise ratios and feeder performance diagnostics." Cooperative system design and implementation The project and process engineers at Lilly and Coperion K-Tron worked together closely during the design and implementation phases of Lil- ly's three CDC installations. Making the process design particularly chal- lenging was the frequent need for the feeders to operate at very low feedrates delivering materials with poor flow characteristics. The sup- plier offered a flexible and responsive approach to customizing the software and control packages, giving the Lilly development team wide scope to explore solutions that would optimize the CDC system feeding operations. The companies' close cooperation proved particularly valuable in devel- oping suitable designs for two of the three CDC lines where it was neces- sary to retrofit vertical arrangements of clustered feeders into existing facil- ities with severe space constraints. The designs also included an innova- tive lift system that supports the main process train and feeders, allowing for ease of access, cleaning, and product changeover. During the implementa- tion phase, Coperion K-Tron engi- neers were on site to help ensure a ment such as mixers downstream from the feeders can be used to com- pensate for feeding variations, this reduces productivity and is only fea- sible for short-term variations, since systemic feeding errors over longer time periods cannot be blended out. In practice, successful implemen- tation of CDC systems ultimately depends on feeder performance. "The Coperion K-Tron control architecture not only allows easy integration with our DeltaV distrib- uted control system but also sup- ports ratio control, where feeders are linked so that subordinate feed- ers respond rapidly to changes in the master feeder's mass flowrate, thereby keeping the ratio of ingre- dients constant," said Tim Pletcher, senior consultant engineer at Lilly. "We find this feature an invaluable aid to minimizing the impact of dis- turbances caused by, for example, feed hopper refilling." It's important to note that distur- bances can still occur in any manufac- turing environment. Addressing these disturbances requires a robust miti- gation system and strategy. Accord- ing to Hanson, "Coperion K-Tron has responded to these challenges by improving their technologies and offering options such as vibration filtering, mechanical and electronic compensation, and a data rich out- tion, the control system has real-time access to information about the true delivery rate and can make this infor- mation available to external systems as an aid to enhancing traceability and quality control. Several years ago, Eli Lilly and Company (Lilly), headquartered in Indianapolis, IN, was develop- ing several CDC tableting lines for Verzenio, a targeted, breakthrough treatment option for metastatic breast cancer. To source the critical gravi- metric feeders for these systems, the company partnered with Coperion K-Tron, a global supplier of process- ing and handling equipment to the pharmaceutical, plastics, chemicals, food, and minerals industries. "Many factors influenced our decision to specify feeders from Coperion K-Tron," said Joshua Han- son, consultant engineer at Lilly. "We knew that the company's prod- ucts have an excellent reputation for accuracy and that their robust con- struction would ensure a long, reli- able working life in a manufacturing environment. The modular design was also important to us, as it per- mits flexible system configuration and reconfiguration." Feeder performance and product quality Not all gravimetric feeders are capable of the performance required in CDC applications. Characteris- tics such as the load-cell resolution and long-term stability, control algo- rithms, and the linearity of the sys- tem that relates the feed screw speed to the measured flowrate all have a major impact on the feeder's overall performance and must be carefully considered, even when choosing among nominally similar gravimetric feeders. This was particularly true for Lilly's CDC systems, where control of feeding operations was to be a pri- mary element of the quality control strategy used to ensure that drug crit- ical quality attributes were achieved. Achieving reliable feedrate control for CDC systems can be particularly challenging because of material vari- ations and the low flowrates that are frequently involved. While equip- Photo 2: Multiple upper-level gravimetric feeders discharge ingredients continuously into a blender on the level below. The feeders are mounted on specialized pivoting tracks to optimize accessibility.