The strong bases statistical associated fluid theory (SAFT) equations of state allow modeling for a wide range of scales and applications. The equilibrium calculations are very time-consuming in SAFT-based family of equations of state; therefore the number of components used in describing a fluid mixture must be reduced by grouping. On the other hand, in some applications it is required to retrieve the detailed fluid description from equilibrium calculation performed on the lumped fluid description. The purpose of this paper is to develop a systematic approach for lumping and delumping with equilibrium calculations using the Perturbed Chain (PC)-SAFT equation of state. The methodology proposed by this paper is to calculate some delumping coefficients from flash calculations performed on the lumped system. Later on those delumping coefficients will be used to retrieve the detailed compositions of the fluid phases from the lumped mixture. To prepare the lumped system, the components are classified into groups through a clustering algorithm and the group properties are calculated according to mixing rules. To examine the accuracy and efficiency of the suggested methodology, it is applied to four synthetic gas samples and two real samples, one being a natural gas condensate and the other one is an oil reservoir fluid. It will be shown that based on the proposed method the delumped equilibrium ratios are close to detailed equilibrium ratios. The observed deviations are small and can be accepted. (C) 2012 Elsevier B.V. All rights reserved.