In this study, we propose the common intermediate storage(CIS) policy which is more efficient than mixed intermediate storage(MIS) policy. The CIS policy is a form of shared storage system, which is extended to overall processes and can be applied to flexible inter-stage intermediate storage policies. Using this strategy, we developed a new completion time algorithm and applied it to two kinds of optimal or near optimal scheduling method; the combinatorial search and the simulated annealing method. We also extended the CIS policy for flexible operation of intermediate storage policy with proper on/off electronic valves and pumps. It thus can be accepted as a basic form of FMS(Flexible Manufacturing System)for operating various storage policies. Finally we suggested the PLC Logic of safety interlock to complement the difficult application of CIS policy, i.e, complication of operation and safety, resulting in a part of basic batch process automation mode.