The modeling and simulation of simulated moving bed (SMB) unit is needed for the choice of its operating conditions; however, it usually does not consider the surrounding equipment (pipe transfer lines, valves, and pumps). The effect of the dead volume on SMB-performance is normally associated with laboratory scale units, where the Volume of the surrounding equipment could represent significant part of SMB unit volume. The presence of the dead volume is also significant in the industrial-scale SMB units applied for production of high purity component; for example, p-xylene. Different techniques are applied in industry to overcome the negative impact of the dead volume on the SMB performance. In this work, the UOP technique for flushing of the transfer lines before withdrawing the extract, applied in Parex process/(industrial scale SMB unit for p-xylene separation) was analyzed. First, the need of the flushing lines was assessed by simulation of SMB unit in presence of the transfer lines' dead volume. The simulated moving bed strategy of modeling was used; the transfer lines' dead volume was introduced into the model through the node mass balances and was assumed as plug flow and continuous stirred tank in different stages of the transfer line use. The transfer lines' dead volume has negative effect on the extract purity. The extract purity falls to 85.54% and 75.22% when the total transfer line dead volume is 0.6% and 1% of the total SMB unit volume, respectively. The advantage of the flushing lines in presence of transfer line dead volume was demonstrated by simulation of Parex unit allowing extract purity above 99.9% and recovery above 98.5%.