Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Chemical and Biomedical Engineering

Committee Chair

Richard Turton.


The uniformity of coating applied to large particles and tablets in rotating-drum coating devices is of significant interest to the Pharmaceutical Industry, especially when the coating contains active material or provides a sustained release barrier for drug transport in a functional coat. As tablets move around the coating drum, they periodically spend time at the surface of the avalanching layer and pass through the spray zone. During this time they receive amounts of coating solution proportional to both the time spent in the spray zone and the area exposed to the spray. The purpose of this research was to quantify parameters that characterize the movement of tablets through the spray region. The three parameters of greatest interest are (1) Circulation time (taucirc), defined as the time between successive particle sightings at the surface of the bed (2) Surface exposure time (tausurface), defined as the time that a particle spends at the surface of the bed within the spray zone during each pass (3) Surface area of the tablet projected toward the spray source (nozzle) during each pass through the spray zone (A tab).;In order to measure these parameters, a digital imaging system was developed and implemented to analyze images of the surface of the tumbling tablet bed. A single white tracer particle was introduced into a bed of black tablets. The tracer particle location and movement at the surface of the bed were analyzed using machine-vision software at a framing rate of 25 Hz. Data for tau circ and tausurface were compared on a qualitative level with previous studies, and similar decreasing trends have been observed in both sets of data with increasing drum speeds, drum loadings, and tablet size. Atab and surface velocities (Vy) were also estimated for the movement of tablets through the spray zone in the rotating drum. This study proves that machine vision software and digital imaging can be applied successfully to the acquisition of tablet movement on the surface of moving beds in rotating drum coating equipment. The independent variables drum speed, drum loading, and tablet size showed significant effects (p<0.05 ANOVA) on the dependent parameters, tau circ, tausurface, A tab and Vy. However baffles were not significant for the circulation times, but influenced the other parameters. Linear regression models were calculated for the dependent parameters assuming linear effects of all the independent variables.