Expert centers promote on-site teamwork--and results.

Metso's expert centers in Jyvaskyla and Tampere supported a team effort that propelled Kymi Paper's PM 8 to world record speeds. How is a world papermaking speed record set? Obviously, the starting point is good technology and a professionally managed commissioning project. But no two papermaking processes are alike; a mill's furnish, production and quality requirements are usually unique. Some on-site changes and fine tuning of the process are an inevitable part of every commissioning project and after the startup curve, when world records are sought after. The teamwork required for machine fine tuning is essential in the quest of world class performance.

In the fall of 2002, the PM 8 base paper machine at UPM's Kymi Paper mill in Kuusankoski, Finland ran at an average speed of 1541 m/min over 24 hours, shattering the world record for freesheet fine paper machines. This achievement attests to the excellent rapport, mutual understanding, and teamwork between Kymi Paper and Metso, the machinery and automation supplier. During the speed trials, this dialogue involved on-site engineers and those at the factories and research and development centers.

At Kuusankoski, this high level of communication and teamwork is aided by a network of expert centers. Two of these centers, in Metso Paper's Rautpohja (Jyvaskyla) plant and Metso Automation's facility in Tampere, Finland, participated in the PM8 speed trials. Experienced engineers at these sites saw the process changing just as the operators saw it. Response tests and trials could be reviewed with the papermakers in the same time frame.

This online information network, which satisfies UPM's security requirements, connects the mill's papermaking process information to experts in papermaking, quality control and process automation. With today's communication networks, this model could be replicated on any paper machine in the world.

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Stefan Fors, PM 8 production manager, sees the value of this communication after the machine startup and during the speed trials. "We saw a very fast response when we were troubleshooting a problem," he said. "The experience in Rautpohja and Tampere has good value. With this service, specialists could be called in more easily to define a problem and determine what follow-up is required. It helps us analyze trials and optimize the machine. Without the remote centers, the problem solving process would have been slower and more costly."

A NARROW WINDOW OF STABILITY

A papermaker will tell you a stable paper machine is a fast paper machine. When the sheet is unstable and breaks are frequent, speed is cut back. If conditions look ideal, papermakers will shoot for as much speed as they can get. Many papermakers, including those on PM 8, will also tell you they operate in a narrow window of machine performance where stability and speed go hand in hand. This window is a particular issue for fine paper machines since the tension in the wet woodfree sheet relaxes. The sheet must be well supported, draws must be gentle, and the sheet must have even quality.

The excellent process stability required for this machine can be achieved only when the process is well measured and controlled. In this respect, PM 8 is one of the most instrumented machines in the world, with associated controls that stabilize sub-processes.

The machine is equipped with a two-scanner PaperIQ quality control system and a metsoDNA control network. In the wet end, seven kajaaniMCAi analyzers measure total stock consistency including ash, five kajaaniRMi analyzers are used to control retention and white water consistency, two kajaaniCATi analyzers report cationic charge demand to stabilize wet end chemistry, and a kajaaniKSF measures furnish freeness. The machine's wet end is stabilized by a multi-variable control called IQWetendMD, which uses the measurements from wet end analyzers in combination with dry end measurements of grammage, moisture and ash. Short-term variations in sheet quality are stabilized at the source before the sheet is formed. Fors likes the stability that this control adds and cites the easiness of the machine startups and grade changes.

PM 8 was the first installation of IQInsight, an instantaneous full sheet wet end moisture measurement system in the first dryer section that detects and corrects wet end instabilities and profile problems and to optimize pressing performance. A Sensodec 6S online machinery condition and runnability analysis system monitors vibration in rotating mechanical components and vibration in roll nips that might lead to poor runnability.

Remote diagnostics has improved problem detection and problem solving. The online information is a useful tool for the paper mill and for papermaking and control specialists within Metso. The online information supports their decisions and recommendations during the speed trials, providing the stability needed to go to the next speed threshold. The cumulative effect of solving many small problems is significant. Removing these obstacles, step by step, can add up to a major increase in productivity.

For example, an engineer in Rautpohja had been looking at excessive vibration in some wire guide rolls. He compared these rolls' irregular vibration curves to normal vibration curves (vibration frequency compared to speed). He correctly deduced that these rolls were filling with water; the problem was resolved without a time consuming in-mill study and further off-line analyses.

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Meanwhile, engineers in Tampere found periodic process instabilities. In one case the stock consistency after the blend chest varied considerably, over a 70-minute cycle, even when the consistencies of incoming stocks to the blend chest were correct. The cause of the variation was isolated to poorly timed operation of washing showers in the disc filter saveall. In another case, the headbox jet-to-wire ratio control became unstable at certain speeds. That problem was solved by retuning the loop. The dosing rate and timing of antifoam agent were also changed to eliminate wet end disturbances. To remove another speed obstacle, bolts on a press felt guide roll were tightened to eliminate excessive vibrations.

The only open draw in the wet end of the machine occurs when the sheet releases from the center press roll. At this point, the delicate freesheet is exposed to a variety of forces--including its own weight and velocity, air pressure balance and adhesion to the center roll. To achieve the lowest stress on the sheet, hence the best runnability and speed, these forces must be in perfect balance.

The mill equipped the machine with a variety of new measurements that give them and Metso engineers a window into this area as well as an opportunity to study it and exert some control over it. Release point, hence release angle, is measured by a laser sensor, average moisture and CD profiles by IQInsight and cationic charge demand by kajaaniCATi. These measurements show how the release point varies with moisture and charge.

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With this sensitivity to release point and draws the papermakers are very aware of changes and how to react to them. "Running over 1500 m/min and with lower grammages the operating window is very narrow and the draws are critical. But, we have been able to hit that window and stay within it," said Fors.

IN THIS ARTICLE YOU WILL LEARN:

* How a new remote diagnostics center aided in machine startup.

* How UPM-Kymmene's PM8 was stabilized after startup.

* The use of remote diagnostics in machine monitoring and troubleshooting.

ADDITIONAL RESOURCES:

* Metso Automation web site: www.metsoautomation.com.

* Metso Paper web site: www.metsopaper.com.

ABOUT THE AUTHOR:

Mark Williamson is a freelance writer based in Thornhill, Ontario, Canada. Contact him by email at [e-mail], or by phone at [phone].