March 2008
By Hugh O'Brian
As part of a long-term strategy to redefine the role of testing in the mill, while also increasing testing frequency for improved operations and process stability, SCA Graphic Sundsvall has for many years been using Metso Automation's PaperLab and PulpExpert automated testing units at its 850,000-tonne/yr Ortviken lightweight coated (LWC) and newsprint paper mill in Sundsvall, Sweden.
Initially used in the mill laboratory alongside the shift testers, SCA has taken a systematic, step-by-step approach to push the PaperLab equipment out to the production floor. Today, it is the paper machine operators who primarily carry out the paper testing function in the mill, bringing them the benefit of faster feedback and a shorter information loop. The results have been very good with the mill seeing better repeatability of the tests and overall improved process stability.
On the pulp lines as well, Ortviken has had a similar long-term vision to automate routine testing and get it out closer to the operators. Since 1995 it has been using a PulpExpert system for on-line monitoring of consistency, freeness and brightness and recently started using a new, more advanced kajaaniPulpExpert unit to carry out pulp properties testing in the laboratory. The next step will be to bring this equipment out in the field for real-time, on-line pulp testing on the fiber lines feeding the paper machines.
Back to 1990
The Ortviken mill has four paper machines, installed between 1958 and 1995, with two of the machines making newsprint and the two newest units dedicated to lightweight coated (LWC) paper. The first PaperLab system was brought into use in 1990 when the mill installed its first LWC machine, PM 1.
The key person behind Ortviken's push to use this equipment and get it out closer to the operations has been Lars Torstensson, the laboratory manager with responsibility for both the Ortviken facility as well as the nearby Östrand pulp mill.
"We began to look at this equipment in the early 1990s when we installed our first LWC line here at Ortviken," explains Torstensson. "At that time the laboratory had about 40 people, working either as shift testers or day employees doing pulp or paper testing. We realized that we were overstaffed but since we were just beginning LWC production and we wanted to make sure that the quality being produced was excellent, we did not change anything immediately."
Running in tandem
Initially, PaperLab was used in parallel, running alongside the traditional manual tests done by the shift testers. "We had heard about PaperLab," continues Torstensson, "And were curious to see if it could help us with this vision we had to redefine the role of testing in the mill. We wanted to improve the reproducibility of our tests and realized that more accurate, repeatable testing could possibly help the stability of our papermaking process. So we installed the first one in 1990 with the new LWC machine but waited a while to gain enough confidence to make changes in our routines."
In 1992, Ortviken was confident in the ability of PaperLab to handle the testing and therefore decided to reduce the staffing to three testers per shift. Thus from 1992 through 1998, the shift tester level remained at three per shift. In the meantime, SCA had started up its second LWC line in 1995, which required some extra testers for startup, once again to make sure that quality was thoroughly monitored during this phase. Also in 1995 a second PaperLab was installed in the laboratory.
In 1998, Torstensson says, the mill had such confidence in the PaperLab and its ability to give accurate and reproducible paper test results that it went down to two testers per shift and even further to one per shift in 2000.
Close to the machines
The success with these initiatives got Ortviken thinking about a more radical step, which would be to eliminate all shift testers. The idea was that by moving the PaperLab out to the machine hall, Ortviken could rely entirely on the system to carry out the testing, with samples fed directly by the paper machine operators. In this manner, says Torstensson, the machine crew would get much faster feedback about any variance in quality.
To do this, in fall 2004 and spring 2005 two new PaperLab Plus units, were installed near the dry end of the paper machines with each PaperLab serving two paper machines. The PaperLab Plus is the latest generation of this testing system, designed to replace the original units, but allowing the internal testing modules to be transferred from the old system to the new one. The unit is designed to be expanded or updated without making installed equipment obsolete.
In May 2005, the move was made so that the operators were running the PaperLab Plus lines. The dry end operators do the testing, taking samples from reels before and after the supercalenders. These are taken to the PaperLab rooms and simply fed into the units, which automatically carry out the testing sequences. The operator does not need to remain in the room while the tests are carried out. If any of the tests are off specification, a warning light seen throughout the machine hall goes off, allowing the machine crew to quickly identify and correct the problem.
The result has been a relocation of the testing 'job', namely that work done in the past with 40 lab persons, is now partly transferred to the operators which has given more efficient process follow up and quality control. Although the lab is still responsible for results accuracy it is the operators who are using the equipment most often and have the direct benefits.
"In the beginning," Torstensson says, "The crews were a bit hesitant about the idea. But they soon saw the value as a tool to help them keep up quality, based on more frequent sampling and faster direct feedback. It is quite simply a shorter information feedback loop so they can react more rapidly. We also see that the machine crews take more responsibility for quality and are therefore more proactive. Previously with the manual tests there was sometimes a question of whether the test results were correct, depending of course on human factors. Now the PaperLab gives repeatable results and we have full confidence in the numbers we get from the unit."
The test modules used at Ortviken in the PaperLab Plus include new modules for tear-P MD and CD, tensile-F MD and CD, smoothness-B, porosity-B, and optical, as well as modules for gloss, caliper, smoothness, PPS and formation that were moved from the old original PaperLabs.
Do the same for pulp testing?
Following the successful experience with automated testing on the paper machines, Torstensson started thinking more about doing the same to automate pulp testing much further.
As mentioned above, the mill had been using a first generation PulpExpert line since 1995 to measure stock/furnish properties for the LWC PM 4. It has eight automatic sampling points (before and after post refining TMP, before and after post-refining kraft, headbox, uncoated, coated and mixed broke) and is used by operators for monitoring consistency, freeness and brightness.
Next step with new equipment
A more recent new development, the kajaaniPulpExpert, is Metso Automation's automated pulp analyzer that works in a similar manner to the PaperLab: Testing is left in the capable hands of the machine. This, thought Torstensson, could be very useful at Ortviken.
"We wondered if we could perhaps do the same thing on the pulp lines to automate testing, with faster, more frequent tests. The pulp mill is making eight different grades of pulp here that are pumped over to the paper mill, depending of course on the paper grades being produced. So it involves a large number of tests and the repeatability and accuracy are very important. After comprehensive testing and evaluation of the results as well as visiting some of the reference mills and the supplier's facilities in Finland, we decided to purchase a kajaaniPulpExpert. After a smooth and effective installation and start-up period the analyzer was in full operation at the beginning of 2006."
The kajaaniPulpExpert is used for lab testing of the pulp samples. The testers manually take a sample and pour the stock into the PulpExpert. The system then automatically conditions the samples and tests properties such as tensile, tear, freeness, consistency, brightness, light scattering, fiber length and shive content. If something is out of spec, alarms notify the operators so they can be aware of it and take the necessary action.
The lab did 3-4 weeks of parallel testing to check the new machine against the manual tests; it also still does a calibration follow-up on a regular basis. But essentially all the pulp testing in the lab is now done with the kajaaniPulpExpert.
The machine can carry out up to 10 times the number of tests that a manual lab can handle, which gives a more accurate, up-to-date, picture of the pulp quality. This makes it easier to detect where a problem is coming from and to pinpoint the right way to solve it faster.
Lower variance and fewer false alarms
The pulp testing results from the new system have been found to show much better repeatability than the manual tests. The variance is lower and the mill processes are operating in a more stable mode. One explanation is that the better repeatability and lower variance means that the operators have better data to base their decisions on and are therefore not reacting to the 'false alarms' that inconsistent testing can cause. "The results we get from the PulpExpert help the operators to clarify where process problems actually are," says Torstensson. "This is very useful for the mill both on the pulp side as well as the paper side."
Torstensson states that his long-term plan is to use the automated equipment in the 'field', meaning more as an on-line process monitoring tool to support the operators directly. "It will probably be similar to the way we did it with the PaperLab. We will use it in the lab to get very comfortable and then move it out into the production area to automate the production line testing."
The benefits that Ortviken has seen with automated testing, including higher frequency of tests, better repeatability, less manual labor, faster feedback time to the operators and improved process stability, all make it hard to see the mill ever going back to the traditional system of paper and pulp quality testing.
At the same time it is important to note that the mill lab is still responsible for the test results, calibrations and accuracy of the tests, and of course quality control. Thus while the activities of the lab personnel have changed, they still play a vital role in overall process and quality control at Ortviken. The key difference is that they are now using modern, automated testing systems for tighter control and, ultimately, improved stability of the processes.
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