Process operators, plant maintenance personnel, and supply chain management must work closely together and should be physically in the same control room.
Another essential feature of modern control systems is the ability to allow for smooth growth. This feature is referred to as their scalability. Scalability is very important in process control, because processing plants are ever expanding, and therefore their control systems must also grow with them. A modular approach to operator stations makes the additions and therefore expansion much easier.
Levels of Optimization
The highest level of optimization is business or enterprise-wide optimization. This includes not only the manufacturing process, but also the optimization of the raw material supply plus product packaging and distribution chains. This is a higher and more important level of optimization than is process optimization alone, because it requires the simultaneous consideration of all three areas of activity and the finding of enterprise-wide operation strategies, which will keep all three areas within their optimum areas of operation.
Plant-wide optimization also involves more than the optimization of the unit processes, because it must also consider documentation, maintenance, production scheduling, and quality management considerations. Plant-wide optimization involves the resolution of the sometimes conflicting objectives of the many unit operations and the envelope strategies required to optimize the entire plant.
At the unit operations level, it goes without saying that multivariable optimization cannot be achieved when individual processing equipment is defective or when control loops are not properly tuned. In addition, it is important that measurements be sampled fast enough and that loops be tuned for fast rates of recoveries. Loop cycling must be eliminated, which usually requires the elimination or compensation for interactions between loops. When no mathematical model can describe a process and it can only be optimized experimentally, empirical optimization is required.
The building of this new generation of control rooms is a challenge to both the suppliers and the users. The suppliers must concentrate on human engineering, so their products will be more operator-friendly, while the challenge to the users is to develop plant-wide optimization strategies.
B©la Lipt¡k, PE, process control consultant, is also editor of the Instrument Engineers' Handbook and is seeking new co-authors for the forthcoming new edition of that multi-volume work. He can be reached at [email protected].
