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Beyond process control to process diagnosis

Analyses, diagnostics and problem visualization functions built into modern DCS and QCS systems
result in better process efficiency

Pulp and papermakers normally deal with equipment wear, some occasional failures and process instabilities. The analyses, diagnostics and problem visualization functions built into modern DCS and QCS systems help to solve these problems for mill teams of operators, maintenance specialists and engineers. The result is better process efficiency and product quality.

When pulp and paper processes are running smoothly you might get the impression they are on auto-pilot. However, when the sheet breaks, a machine fabric is lost, something changes unexpectedly or fails the operators must react quickly to return to some state of relative stability. It’s not smooth sailing all the time.

Modern automation systems have opened up the process for a more transparent view by mill staff - including operators, maintenance technicians and engineers. Today, many planned or impromptu meetings to solve problems take place in the control room.

Information is good; diagnosis is better

However, there are remedies to these problems in modern automation systems. Quality control and distributed control systems have opened up a vital stream of information about the process, the machinery condition and product quality for a more transparent and consolidated view by mill staff. While information is good, diagnosis is even better. That is why analytical and problem visualization tools are now proving their worth by helping mill staff to resolve and avoid the re-occurrence of mechanical, process stability and quality problems. The extensive use of these problem-solving tools underlines the old engineering adage – if you can define a problem you can usually solve it.

With the integration of many more measurements, analyses, diagnoses and problem visualization functions it is now possible to determine the root causes of mechanical, process and quality problems. Moreover, with the essential input of human interpretive skills, it is possible prevent them from recurring. By looking out for telltale signs of instabilities or imminent failure and by keeping track of key performance indicators, mills can prepare for necessary corrective actions, nip problems in the bud and therefore ensure high process efficiency.

Stora Enso is one company who recognized the value of this problem-solving collaboration when they set out to design the control room for the PM12 production line at the Kvarnsveden, Sweden mill. This central meeting point is where mill employees of various job functions and suppliers can get together and look at the real-time data and solve current problems. The success of this concept relies on readily available information from the control room user interfaces - the operators’ windows on the process. The need for this purpose-designed meeting point is by no means unique to this mill. In fact, all mills should consider how meetings are arranged and how the data and diagnoses from automation systems could be - and should be - a central part of the solution process.

If the day comes when automation systems are smart enough to solve problems automatically then mills may be on true auto-pilot. But pulp and paper process and quality disruptions today must be solved by human interpretation and collective problem-solving skills. In this regard, the process insight and visualization available in today’s automation systems can be a major help.

By Seyhan Nuyan & Mark Williamson

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Beyond process control to process diagnosis
Issue June 2012 of Pulp & Paper International (PPI) magazine PDF