Like-for-like plant controls upgrades: When are they an advantage?

Plants are facing the need to upgrade much of their automation systems and electrical gear due to age and obsolescence. However, the question that managers face is how much of the equipment do I need to replace and to what level does it need to be replaced. Do I just change out the computers and update the HMI or do I replace the entire control system with new more advanced controls that provide solutions I know I’d like and features that will improve the plant for the next 20 years. This is a case of “do I want” or “do I have to have”. Each plant is going to have a unique answer and neither is wrong. The paper explores the question and various answers regarding when a simple like for like upgrade is needed or when plants should do more.