Comparison of cleaning of toothpaste from surfaces and pilot scale pipework

Experiments have been conducted to study the cleaning of toothpaste at two length scales. Laboratory scale cleaning studies have been conducted on fouled coupons in a horizontal flow cell. At pilot scale, the cleaning of fully fouled pipes has been studied and monitored by temperature, conductivity and turbidity probes. Removal from the pipe occurs in two steps: core removal, leaving a thin wall layer that is then removed by thin film removal that takes the majority of the cleaning time. At both scales, cleaning time is influenced by temperature and velocity of the cleaning fluid. The pipe length range studied, 0.3–2 m, does not appear to have a significant impact on cleaning time. Cleaning time correlates well with (shear stress)^?1. A dimensionless cleaning time is defined and a correlation between cleaning time and Reynolds number developed.