Making it all add up

Although it started up back in 1990, the 5.25 m wide, 350,000-tonne BM5 at FS Karton in Neuss is still one of the largest and most modern recycled boxboard machines in Europe. And every January, the mill makes sure it stays that way – with new improvements.

Udo Koolen, FS Karton’s Project Engineer, explains why FS Karton chose ANDRITZ to carry out the latest upgrades. “ANDRITZ knows the machine – they built it. But also, I like that we got everything from one supplier that took responsibility for all the work, including the actual installation – not all suppliers offer that.”

BM5 uses four fourdrinier formers to make boxboard - first top layer, second top layer, filler layer, and back layer. As part of a full headbox service, ANDRITZ installed new bottom and top slice lip and renewed all seals. “We took it completely apart,” says Johannes Kraxner, Service Manager, ANDRITZ Tissue, Paper & Board Machines, “which has given us benefits such as improved cross-direction and machine-direction basis-weight control and correct sealing on the mixing chamber right from the start-up.”

DRYING CYLINDERS – “A VERY SKILLED JOB”

Downstream, the dryer section at Neuss comprises 44 pre-drying cylinders before the MG cylinder, followed by 21 after-drying cylinders. ANDRITZ installed three new 1.8 m diameter, 5.7 m long, PrimeDry Steel cylinders in the pre-dryer section, replacing three cast-iron cylinders.

The new steel cylinders can operate at much higher parameters (6 bar pressure, 1,200‑m/min speed) than the cast-iron cylinders. For now, though, Neuss has already achieved its immediate goals of more homogenous heat transfer, smooth runnability, safety, and a return to design quality.

And it wasn’t easy. Koolen comments, “I was very impressed with how ANDRITZ installed the drying cylinders. It was a very skilled job; they had to be precise down to the millimeter.”

MG CYLINDER – A BALANCING ACT

Although the MG cylinder is in the middle of the dryer section and runs hot, it is not actually used for drying. Instead, it ensures a smooth printing surface on the white top layer of the cartonboard and liner produced on BM5.

Over time, line pressure had resulted in the MG cylinder becoming marginally eccentric, by 0.6‑mm over a diameter of 6,400 mm – but even that was enough to require re-grinding of the cylinder. “It wasn’t a problem that was obviously noticeable,” Koolen says, “but it was causing the cylinder’s three doctors to move and was affecting the main bearings."

The grinding reduced the overall diameter by 1 mm, ensuring that the MG cylinder was perfectly round and smooth again, increasing machine stability and product quality.

The service in January also included two new PrimeRun M web stabilizers, in addition to two PrimeRun M units that ANDRITZ had installed six months earlier.

Koolen concludes, “Technologically, everything went smoothly. The sealing in the headbox worked. The cylinder set-up was a reward for good preparation and discussions between ANDRITZ and us. We did what we planned to do and achieved everything we wanted and the start-up took place with no project-related problems at all.”

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