Batch process which is operated in a unsteady state mode is subject to various process imbalances. Consequently intermediate storage vessel can take an important role for mitigating parameter variations, increasing plant availability and providing flexibility in sequencing and scheduling. A mathematical model of intermediate storage vessel sizing in parallel batch units subject to batch failure is derived. The case in which the inlet flow rate to the storage vessel is greater than or equal to the outlet flow rate from the storage vessel followed by the opposite case is considered. Two operation mode is considered, that is, in-phase operation and out of-phase operation. In phase operation refers to the delay times in parallel units while out of operation to distintly different delay times in the set of units. Analytical expressions for the limiting volume are obtained for several network configurations, i.e. multiple input single output(MISO) system, multiple input multiple output(MIMO) system and serial system.