By John C. Hollemans, ing, B.A.Sc., M.Sc. P.Eng.
After a plant has been built, it has a control system that reflects the “state of the art” at the time of construction and commissioning. It then typically operates with the “as built” controls for many years. In a complex refinery or chemical plant, many process units are typically added or modified over a number of years. So, we end up with field instrumentation, controls, and control rooms that are probably very dissimilar. This leads to the usual maintenance challenges because we must deal with many different product vendors, spare parts that are becoming harder to get, and often find ourselves in a situation where modern network technologies cannot be used to extract and store process data for archiving and analysis. In addition, there may be too many control rooms that require significant upkeep, and that do not meet current “best practices” standards.
Many studies have been done over the years that show how modern process control systems and well designed control rooms have contributed to significant increases in product quality and yield, while at the same time reducing energy consumption. The comfort level of the staff running the plants has also improved.
Instrumentation and process control systems can be upgraded in order to capture those product and energy related benefits. This is best done by doing an “Instrumentation and Control System Revamp” study (I&C Revamp). A typical I&C Revamp study has these steps:
We plan to present the typical costs and benefits of a control system revamp project in follow-up articles. We will also describe what control systems technologies are currently being implemented, explain in some detail what the advantages are, and where the biggest “Bang for Buck” can be expected.