Reimagine the advanced process control paradigm

The time is opportune to rethink APC

By Allan Kern, APC Performance LLC

Preview

  • In the wake of robust advanced process control (APC) activity for several decades, industry now finds itself with an APC paradigm that is largely obsolete, often unhelpful and sometimes misleading.
  • The time is opportune to rethink APC to shape an updated, more accurate, realistic and useful paradigm to form the basis for greater APC success going forward.

Role of advanced process control

Figure 1 is the most traditional and fundamental way to summarize the essential role of APC in real-time process control and optimization. It can be elaborated upon as follows:

  • APC can keep a process closer to constraints, because its automated nature means that it can back the process away from encroaching constraints in a responsive and reliable manner, should that become necessary due to unexpected disturbances or changes in process conditions. By the same token, APC can automatically pursue constraints as they move further away, capturing additional earnings.
  • In the absence of an automated APC application, operators tend to keep the process further from constraints in order to provide greater time to respond and a wider margin of error, should manual intervention become necessary. This greater distance from constraints typically translates into a cost penalty in terms of an incremental loss of capacity, yield, energy efficiency, etc.

This way of viewing and understanding the essential role of APC in process operations remains perfectly (and very usefully) valid today. However, several other aspects of the original paradigm have grown obsolete, unhelpful or even misleading.

Legacy APC paradigm

Figure 2 summarizes several gaps between the legacy APC paradigm and a reimagined paradigm that embraces experience gained, lessons learned, and more realistic goals and expectations from today’s vantage point. Where issues remain unresolved—as several core issues do—the reimagined paradigm fills in with promising possibilities so that it can also serve as an APC vision going forward.

One pillar of the conventional paradigm is that APC is highly specialized and expected to remain so, but the general trend in the reimagined paradigm is to evolve APC toward a core-competency at the industrial process operation level, where more agile, affordable and smaller-footprint multivariable control tools are needed for both process automation and process operation objectives.

The gaps in the current paradigm have undermined efficient communication between stakeholders. An updated paradigm that more accurately reflects the technology today and that accepts alternatives to some of the persistent root issues, which have impeded APC progress in the past, will help APC to more rapidly move forward again.

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