To process a greater variety of materials and improve global competitiveness, Mitsubishi Chemical Corporation's Kashima Plant (Tobu Zone) and Mitsubishi Chemical Engineering Corporation contracted with Chiyoda Corporation in May 2004 to construct an additional fractioner for an ethylene plant. Yokogawa's CENTUM CS 3000 R3 was selected as the new control system. After carrying out an extensive study, the customers decided to employ ProSafe-RS as the emergency shutdown system instead of conventional relay-based systems in order to:
By introducing the ProSafe-RS, the Kashima Plant improved safety, reliability, monitoring, and operation as follows:
Takayuki Aoyama, Team Leader of the Instrumentation Group at the Maintenance Technology Center, commented:
"Usually introducing a new thing takes time: you must collect various kinds of information about it, then study actual records, reliability, and technological factors. This is even more so when you consider introducing a product that is used to guarantee safety.
This is where ProSafe-RS comes in. Safety instrumented systems can be evaluated according to international standards and certified by a registered certification body. This spares users the trouble of conducting a feasibility study. The safety standards cover a wide range of items and are thorough about maintaining safety during the detailed design phases. As the system design utilized probability theory, engineers are better able to give a logical explanation of it to third parties.
Introduction of the new safety system was a big decision for us as the existing interlock used hardware relays. As we understood the standards as well as the configured actual hardware and software, however, we were convinced that the new system took safety into much greater consideration than conventional systems and that we had made the right decision.
Interlock-related equipment is growing more complex as it is required to ensure safety against all types of failures, and the same was true when panel instruments were replaced by distributed control systems (DCS). For this reason we employed the ProSafe-RS safety instrumented system. We also believe that the time is approaching when all hardware relays will be replaced by CPU-based systems."