Emerson Exchange 365

The speedup of a plant’s response can cause loops to go from a smooth to an oscillatory response. In actual plants, the faster rate of change of a process variable important for product quality such a temperature or composition occurs for various changes in operating conditions. Principal sources of speed up in an actual plant are a smaller mass due to minimization of inventory or at the start of fed-batch operations, an increase in heat transfer coefficient from a cleaner surface or higher fluid flow, and an increase in catalyst activity from fresh catalyst or higher fluid flow.  In virtual plants, an increase in integration step size in first principle models is used for simulation speedup so scenarios take minutes instead of hours to complete. This speedup of simulations is essential for training operators and developing/prototyping control strategies. The bottom line is that the product of two terms can be used to detect and prevent instability in plant speed up. Read the full text.