Are our mills on auto-pilot? Not by a long shot!

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

Mark Willliamson

When you enter a modern control room in a pulp and paper mill you might get the impression that the process is on auto-pilot with the operators comfortably supervising the process through a myriad of video monitors, maybe tweaking a control loop setting now and then or turning something on or off by remote control.

Idyllic and futuristic looking, isn't it? That is the case many times when things are running smoothly, but then the sheet breaks, a machine fabric is lost, something changes unexpectedly or fails the operators must scramble to recover to some state of relative stability.

In pulp and papermaking processes things wear, become unstable or break from time to time; that's the reality regardless of the degree of automation. It's true that process controls can keep running and maintain targets but any notions of an auto-piloted process must be dismissed quickly when these mechanical or other disturbances happen.

These production instabilities, interruptions or outright failures result in lower productivity and sometimes costly downtime. Worker safety can be compromised as well. However, there are some promising signs that remedies can be found in modern automaton systems which have opened up vital information about the process, the machinery condition and product quality for a more transparent view by mill staff. Problems are now being solved using the DCS' or QCS' new capabilities.

Problem visualization

With the integration of many more measurements, analyses, diagnoses and problem visualization functions it is now possible to determine the root causes of these problems and, with human interpretive skills, it is possible prevent them from recurring. In some cases, looking out for telltale fingerprint signs of instabilities or impending failure can help mills to prepare for necessary corrective actions, nip the problem in the bud and therefore ensure high process efficiency.

Some of the problem diagnosis and visualization features have been added quite recently. Rather than functioning as the digital equivalent of the pneumatic controls and manual operation they replaced many years ago, DCS and QCS systems have evolved to become much more helpful to operators, process engineers and maintenance staff working as a team. It's long way from the time when pulp and paper mills dutifully stored printed production summarizes that were seldom used and just gathered dust. Today's information is active, visible and developing as the discussions go on.

The process of problem visualization started in the 1990s with the integration of former PLC-based machinery controls and interlocks in the DCS system. By displaying the previously hidden logic functions the causes of halts and startup problems could be diagnosed and solved quickly, thereby helping the process to start up quickly. More recently, machinery condition monitoring has been added to the diagnostic capabilities of the DCS allowing operators to see if a particular machine component or bearing is vibrating too much or showing signs of wear. And this information is displayed on the same screen which is used to control the process. Operators don't need to know the intricate details of vibration analysis; they just need to know something is abnormal and ask some maintenance technician to see if it is serious enough to fix right away or wait until the next shutdown. Some problems like polymer roll hot spots need immediate attention.

Ebedded analysis

This integration of condition monitoring in a DCS comes at a time when maintenance and production departments in pulp and paper mills are developing programs to coordinate their efforts in maintenance planning and predictive maintenance activities in order to ensure production goals are met and maintenance is focused on well-defined needs. The embedded condition analysis function in a DCS will therefore promote these cooperative maintenance and production planning programs and help mill staff to target maximum process availability and cost-effective operations.

Rather than being in the corner of the control room or in the maintenance shop the condition monitoring visual displays are right in the center of action and immediately recognized by operators. In an article entitled "Operators in Maintenance" Mr. Christer Idhammar of Idcon Inc. emphasizes the importance of involving operator in an effective preventive maintenance program. He says, "To include operators in essential care of equipment including preventive maintenance inspections is one of the reliability and maintenance improvement initiatives that can yield the best return on investment. The investment is low and results in increased reliability and lower maintenance costs can be substantial. Still, very few pulp and paper mills can claim that their operators are involved to a significant extent in these activities." That may be changing now.

This embedded analysis in the DCS also extends to process valves and field instrumentation. With this tool, the performance of valves can be followed closely and impending problems with their response can be flagged and maintenance can be scheduled proactively before process stability or uptime is affected. The cost of maintenance is lower since repairs are done only when indicated.

Detective work

With advanced spectral analysis QCS systems analyze the variability of product quality measured online and relate it to process instabilities. In many cases, this detective work by mill engineers can lead to better quality and process efficiency. In the pulp mill, where many instabilities are related to raw materials and unstable process flows, fuzzy logic is used to deduce the common sources of process problems and the corrective actions based on experience. One experienced operator at a Finnish mill said that the indicators of good or bad chip column movement and other performance indicators help the production team to devise new operating strategies to continuously improve their operation.

There are many new DCS-based diagnostic tools which can help the operators, maintenance technicians and engineers to detect and solve problems. Many of these tools are available on desktop computers which allows more detailed analysis remotely - away from the hustle and bustle of the control room. In fact, paper engineers and production managers can follow their process state at home through an Internet connection

But papermaking or pulp making problems are solved most often by team effort, and this involves meetings and discussions - either planned or impromptu -where the action is happening and where the diagnostic information is readily available. The best place is often right in the control room.

blog3MW-photo2Many machinery and process diagnostic tools are available on desktop computers which allows more detailed analysis rather than in the hustle and bustle of the control room. In fact, paper engineers and production manager can follow their process state at home through an Internet connection.

Stora Enso recognized the value of this problem-solving collaboration when they designed the control room for the PM11 production line at the Kvarnsveden, Sweden mill. This control room is intended to be a central meeting point where mill employees of various job functions and suppliers can convene and look at the real-time data and solve current problems. 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 let's hope that day is far off. Solving problems is what challenges us and keeps up our vitality. Process insight helps a lot.