"Process design is based on steady state conditions -- process variables, and physical and chemical parameters, are assumed known, fixed and time invariant. However, refinery and chemical plant operations are never at steady state, and it is the transient nature of real-world operations that makes process control an essential requirement for achieving safe and acceptable plant performance. The primary roles of the process control strategies implemented in an operating plant are to (i) hold plant operations at a desired operating point despite process upsets, (ii) provide smooth, fast and safe transitions from one operating point to another, and (iii) keep plant operations on the safe side of limiting process constraints. The control strategy design fundamentals described and discussed are applied to develop numerous specific control strategies in a wide variety of realistic process configurations."-- Provided by publisher.