Visualization investigation of the motion of rags in a double blades pump

Accumulation of fibrous materials often leads to pump clogging in wastewater systems. Visualizing these clogging phenomena helps identify ways to reduce the risk. In this study, we analyze a double blades pump made of acrylic glass using a fast digital camera to record the motion of rags inside. Recordings at three rotational speeds investigate the impact of rag materials, sizes, and quantities on their passage through the pump. Results show that smaller rags pass through the pump more quickly. At the same rotational speed and with the same material, the maximum passage time increases by over 100% compared to the shortest passage time. Additionally, rags flow more rapidly at high impeller speeds. At low speeds, rags tend to linger inside the impeller or stick to the pump casing’s tongue. The passage time at high speed is about 10% less than at lower speeds. Furthermore, under the same mass concentration, larger rags with fewer quantities are more prone to clogging than smaller rags with greater quantities. The proportion of larger rags with fewer quantities smoothly leaving the pump is about 10% less than that of smaller rags with greater quantities.