Chemical Processing - January 2008 - (Page 35) technology instead of how well the system allows operations to improve the manufacturing process. When DCSs first became available, the process control engineering department chose or at least strongly drove the choice of system. Selection was centered on the ability of the control system to meet certain technical standards and the initial sales price. Operations wasn’t involved much if at all in specification and selection, and real analysis of operational improvements wasn’t done. Leaving operations out of the selection process usually led to a system that wasn’t friendly to the operator. Related process information was scattered on numerous graphic pages, causing the operator to have to toggle among several graphics. While this may be tolerable during normal operation, it can become time consuming and frustrating when abnormal situations arise and the operator needs to manipulate the process and closely monitor measurement readings. Modifying the system may be difficult and may need the assistance of a system engineer. So, operations management may resist changes in graphics suggested by the operator. Also, it’s very likely that any complex control strategy will be abandoned if it’s not easy to use and troubleshoot without the presence of a system engineer and the process run in a manual mode. • 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. www.chemicalprocessing.com 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 maintenancebased 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? The automation design must focus on providing financial benefits in the process area. This infers an audit of the process unit must be done to identify areas for financial improvement. It’s important to define the problem before designing a solution. A key preliminary To properly establish a modernization plan, it’s crucial to conduct a conceptual engineering study. While each study should be done on a custom basis, most consist at least in part of the following major activities: • establishing the current process baseline; • setting business and process operation goals; January 2008 • 35 http://www.chemicalprocessing.com
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