2013-06-24 - At the Chillicothe mill in Ohio, 400,000 tons of specialty papers are produced a year on four paper-making machines. Using ABB’s Extended Automation System 800xA paper production variability is kept to a minimum.
By ABB Communications
The mill in Chillicothe, Ohio.
The Chillicothe mill has produced paper for over 120 years, expanding from the Ohio 5-acre site, built in 1890, to the present 350-acre site staffed by 1,300 employees. The site houses a timber yard, a bleached Kraft pulp mill, which is used to change wood to wood pulp, and eight batch digesters, four boilers, a coater and a variety of paper converting machines.
On site, the largest of the four paper-making machines known as "The Chief" was built in 1980 and renovated in 2000. The Chief produces a wide range of specialty products in a variety of basis weights (a measure of paper density). Since Glatfelter acquired Chillicothe operations in 2006, The Chief has been transformed to produce a varied mix of products in keeping with the corporate vision of "becoming the global supplier of choice in specialty papers and engineered products."
Over the years an important part of Glatfelter's continuous improvement efforts has been to reduce product variability, but as the product mix has diversified and the printing and converting equipment has evolved, this has become increasingly difficult. Chemistry improvements have been made over time and the mix of products has changed, leading to coating buildup on the caliper gauges, which has in turn resulted in measurement errors. To maintain consistent paper quality, the caliper gauges had to be cleaned after each full scan. As Chad Biddix, stock preparation superintendent explained, “Bad readings create false control actions, which result in low-quality products, internal rejects and ultimately in low-quality yields.”
Quality yield is a critical key performance indicator (KPI) for Glatfelter, and is one of the primary continuous improvement initiatives of the plant, so when further problems resulted from poor caliper control, including an increased frequency of ridging, roping and wrinkling, the only solution was to bypass the control system and manually set the profiles. At this time it was clear a better solution was required.
Glatfelter could see that improved caliper measurement was the primary solution to the problem and after meeting different vendors, they opted for ABB’s Extended Automation System 800xA to improve quality control, including two Network Platform NP1200 scanners with optical caliper sensors, one at the size press and the other at the reel. These optical caliper sensors stabilize the sheet on one side and then make a confocal, non-contact measurement on the other. What convinced Glatfelter personnel that ABB had the right solution was a visit to the Stora Enso mill in Sachsen, Germany, where they saw impressive results of a similar ABB system in action (PPI, January 2010).
After startup, in May 2010, the results at the Chillicothe mill were immediate. Internal rejects due to caliper errors or mechanical defects caused by poor caliper control were virtually eliminated and the time taken to make paper-grade changes, a frequent requirement of specialty paper-making machines, was drastically reduced.
An important performance parameter of specialty paper-making machines is the time it takes to make quick paper-grade changes.
"Working together with ABB, our control group developed an automated paper-grade change process, which allowed us to make paper-grade changes with no losses. Even when making the most challenging of changes, we can now reach the right specification within seven minutes. This means that paper-grade changes have less than a one percent impact on our efficiency. The number of paper-grade changes we make is very challenging and extremely dynamic. We need to perform and we rely on the system to deliver for us," said Randy Dittman, The Chief’s superintendent. “In addition, despite all of the paper-grade changes this machine makes, the winder on The Chief remains one of the most productive winders in North America,” said Dittman. "The paper must be perfect before going to the winder, which runs at 8,500 feet per minute (that’s just over 43 meters per second). If it runs well on our winder, we have confidence it will run well on our customers’ winder too."
To maintain optimal paper quality ABB now has five people working full-time at the mill on a full-service contract for the platforms. This includes maintenance, tuning and optimization.
"The ABB system was the right decision for us,” says Dittman. “The service relationship is the best I've seen in my career. The system is very reliable and if an issue arises, the local service team is proactive and quick to resolve the problems."
Since the new system was installed, Glatfelter has continued to seek out ways in which to reduce variability in the process. “With ABB’s technology we are able to study the frequency of disturbances in The Chief,” said Dittman. "It has allowed us to link changes in performance to process upsets. This means we are able to identify and eliminate sources of variation. We can test as much as we want to test. The online spectral analysis has been a big help with all of this."
Biddix believes that a lot of the benefits achieved on The Chief can be replicated on the other three paper-making machines in the complex. While these machines are smaller in scale, there is a clear opportunity to utilize the engineering approach that has been used on The Chief to obtain similar results.
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