- Process problems weren’t fixed because the control system was expected to overcome them.
Modern control systems, along with properly installed instruments and valves, can allow major improvements in operations. However, faults in process design or equipment may negate the advantages of automation. Performance after the implementation of a new system may be disappointing if a thorough review isn’t done to identify the existence of process or mechanical issues — e.g., related to agitation, heat exchange, undersized units and shared equipment. A control scheme sometimes can overcome a process-related issue but generally the robustness of the control strategy will be low and circumstances will occur that will cause poor operating performance.
Be leery of promises made by sales people in competitive situations. The system vendor may oversell the features of the control system when a bid specification focuses on them and low cost.
- The existing process control system was replaced in-kind.
There are many excuses for why systems get replaced in-kind. Two stand out. First is the desire by management to keep the cost of the replacement as low as possible. This typically means system obsolescence was used to justify the replacement, which, as mentioned earlier, usually is a dubious approach. Driving down the cost of the new system becomes the primary goal of management. No process or operations reviews are conducted to assess areas of poor performance and to design in new control strategies or instrumentation to improve operations.
The second reason is operations management’s desire to not alter the “look and feel” of the system so the operators aren’t confused. This really is unfair to most operators. Sure, there’ll always be the operator who doesn’t want change. He’s the one who goes through the local gauges and the single loop controllers and marks the normal operating point with a grease pencil. Such an operator tends to run the plant by rote rather than by really understanding the operation and the actual impact of his actions.
However, most operators desire a better method to run their plants and already have experience with computer technology throughout their private lives.
Establishing the business goals
So, how is modernization of the automation system properly planned and implemented to achieve financial benefits?
First, it’s important to correctly define “process automation modernization.” It isn’t replacing one control system with another. Instead think of it in a broad sense.
Process automation’s scope must include instrumentation, automated block valves, and final control elements such as control valves and adjustable speed drives. You also must consider integration of information between the process area and the plant’s business. Finally, take advantage of the additional instrument-specific data available with HART and Foundation Fieldbus devices through digital communication, along with maintenance-based asset-management software, to improve operations — for instance, advances in centrifugal pump monitoring use Foundation Fieldbus as an infrastructure to communicate information on unit health to the maintenance shop.
Second, the design must consider the company’s business direction. Questions to address early include: Does the business need additional production capacity, or does capacity suffice but manufacturing costs need reducing? How important is it to distinguish products from those of competitors? What’s the competitive situation? Is the company the market leader? Is business volume in jeopardy of being lost? Is this facility the only maker of certain products within the corporation or do several sites make the same products? What is the marketing department opinion about a product’s future? Are sales rising or declining? What values do the customers appreciate and what can be done to increase sales?