Floatex Density Separator (FDS) is an advanced hindered settling classifier and autogenous teetered bed separator, which utilize particle settling rates to segregate different particles according to size, shape and density. In coal washery FDS is being employed as pre-concentrator as well as classifier. Though enough literature is reported on FDS for coal cleaning or de-shaling purpose, but there was no appreciable work carried out on the effect of process variables on classification performance while treating coal. Therefore, the present study focuses on effect of different process parameters like teeter water flow rate, set-point, feed rate and pulp density on particle classification while treating fine coal. Statistically designed experiments were carried out and their effects on performance in terms of yield to under flow, cut size (D-50) and classification efficiency (EP) has been evaluated. Different regression equations were developed to describe and predict the performance of floatex density separator. (C) 2013 Elsevier Ltd. All rights reserved.