Numerical modeling of conventional spin-stop agitation of liquid drug products for automated visual inspection

The inspection of liquid-filled vials and syringes using automated visual inspection (AVI) machines is a common practice in pharmaceutical production lines. Liquid drug products are typically agitated using a spin-stop motion to detach particles from the interior surface of the containers, thereby maximizing the probability of their detection. A numerical model for an ISO 8362-1 6R glass vial was developed and validated to qualitatively assess the agitation process for a range of motion profiles, liquid drug product properties, and fill volumes. The results show that increasing the angular acceleration and maximum velocity of the agitation increases the total wall shear force during the spin-down, where the wall shear stress (WSS) distribution covers the entire wetted interior surface of the vial. Our results suggest that high angular acceleration during the spin-down phase maximizes the WSS distribution across the interior surface, in turn maximizing the mobilization of contained particles. A comprehensive computational fluid dynamics model is presented that is adaptable to other container formats and liquid product configurations. Understanding how to maximize the shear stress distribution while minimizing residual formation can inform the optimization of the AVI processes on a per-product basis.