Control of a System of Loss-in-Weight Feeders in a Continuous Manufacturing Drug Product Application

Dispensing materials using loss-in-weight feeders is a critical unit operation in most continuous drug product manufacturing processes. As feeding is typically one of the furthest upstream operations, its output has a large influence on the rest of the process. Through experience continuously processing several pharmaceutical formulations, several common feeding problems have been identified including high variability feeding, drifting from set point, and transient disturbances. This work discusses the control of a system of feeders in addition to individual feeder control, showing examples of how a system level ratio control loop can be used to mitigate these common feeding issues and provide consistent output to the downstream process. In addition, identifying special cause transient disturbances from the feeding operation using different types of feeder data will be discussed.