In this study, the effect of solid particle settling velocity on the mean critical mixture-flow velocity in a pipeline system is investigated. A graphical method proposed by Mitzmager (1964), for a quick and reliable calculation of particle-settling velocity, is used in the analysis. Following dimensional analysis applied on the main parameters of the problem the most suitable non-dimensional form of critical flow velocity is obtained from the application of regression analysis on the available data. Comparison of obtained equation with similar ones proposed by other researchers is given both in tabular and graphical forms. The expression given in this study estimates the mean critical flow velocity in a pipeline system much better than the other expressions.