Faster machine speeds are forcing suppliers to step up the pace of forming developments

Winning the race to stay on top form

Looking ahead, the race toward faster production is likely to intensify for the industry's suppliers. As a result, the suppliers are stepping up their research into forming developments to keep up with the pace of papermakers' demands and that trend is translating itself into new forming section designs.

DuoFormer developments

One of the latest machines to hit the market is the DuoFormer TQv from Voith Sulzer. The new unit is especially designed for machine speeds of up to 2,200 m/min. The newest addition is based on the roll blade forming concept and is mainly intended for use with woodcontaining or woodfree grades. According to Voith Sulzer, the design is aimed at improving the paper quality, wire life, speed potential and cleanliness of the PM.

Voith Sulzer’s DuoFormer TQ

A clue to the main difference between the supplier's previous technology and the new design is to be found in the "v" in TQv. The v represents the vertical arrangement of the forming shoe and counter blades. As product manager forming for graphic papers at Voith Sulzer, Hans Moser, explains, "Before, the equipment (the DuoFormer TQ or CFD) was always arranged horizontally or on a 45° incline table. But for high speeds, the vertical arrangement is better. It is simpler to remove the water and you don't have to work against gravity. But you do have to make more of an effort to keep the counter blades clean."

The main advantage with the vertical arrangement can be found in the water removal characteristics. The new design also avoids suction deflectors and weirs in the shoe, according to Moser. The DuoFormer TQv has a fully revised design for the twin-wire section. A ModuleJet headbox delivers the stock into the gap created between the top and bottom wire. Initial drainage starts at the suction forming roll, which promotes good retention, according to the supplier. The roll is followed by the D-section, or blade forming section. This unit consists of a curved suction box located in the transfer wire loop and forming blades located in the top wire loop. The forming blades are loaded with a pneumatic system against the suction forming box and a wet suction box is placed after the D-section.

The sheet then travels over a couch roll with two vacuum chambers. According to the supplier, the first vacuum chamber provides additional drainage in the twin wire section, while the second provides a safe sheet transfer to the bottom wire and further increases dry content. A high vacuum flat suction box ensures sufficient dryness before the web enters the press section.

Voith Sulzer hopes to see its new design go into action later this year. One new unit will be installed at Perlen Papier in Switzerland, while another is set to come on stream at Haindl's Schongau mill in Germany.

Heavy weather

On the other side of the Atlantic, Beloit has had a rather more turbulent year. Uncertainty has been raging over the company's future ever since the supplier's parent group was forced into Chapter 11 bankruptcy protection last year. Going into 2000, the uncertainty issue seems to have been solved, on paper at least, with bids for the various parts of the company being accepted in January of this year. The paper technology division has ended up in the hands of Mitsubishi Heavy Industries, but the company's future moves in the forming area remain a mystery for the moment.

Despite all the problems, Beloit's troubles did not stop the company's forming division from coming up with a number of new developments over the last 12 months. For example, Beloit plans to start up its first reverse Bel Liner this year at the Premier Box Board company. The new unit will operate as a mid-ply former, followed by a regular Bel Liner for the top ply. The main advantage of the reversed configuration is that it requires less overall MD (machine direction) space than the regular Bel Liner and fourdrinier, the company explains. The new design also has a higher drainage capacity compared to the regular Bel Liner.

In the current economic environment, new installations are few and far between in the paper industry - a problem which Beloit understands all too well. For this reason, the company has also been developing a number of upgrade services in the forming section, which can boost a machine's performance. One area where papermakers can squeeze that extra ounce of efficiency is in the counter blades. Upgrading the counter blades on an existing Bel Baie former is a simple rebuild that requires minimal downtime, according to Beloit. The rebuild is aimed at increasing dewatering capacity on the machine and improving sheet formation. The upgrade involves installing a new counter blade unit with scoop shield and mountings. In some cases, the second deflector can be replaced by a counter blade deflector.

Recently, a Bel Baie II former was upgraded to include counter blades at the International Paper/Aussedat Rey mill in Maresquel, France. The rebuild consisted of a new counter blade unit, mountings and rework on the second deflector. The upgrade allowed the mill to produce heavier basis weights of fine paper consistently. The project also increased the dewatering capacity on the machine. As a result of the increased drainage capacity, wet end related sheet breaks have fallen and machine efficiency has increased.

Optimal installations

Although Valmet did not launch a major new forming design last year, the company was far from idle as it installed a number of OptiFormers across the globe. Since PPI's last forming 12 months ago, Valmet has seen OptiFormer units start up at three mills.

The first mill to dabble in the new concept was Steyrermühl in Austria, which treated its PM 3 to a major overhaul in the second quarter of 1999. This project was followed by another ambitious rebuild at UPM-Kymmene's Nordland Papier mill in Germany. The third unit went into action at Nanping's mill in China in the middle of December last year.

So far, the OptiFormer has been well received at the mills. According to Jürgen Hoppe, vice president of technology R&D at Nordland Papier, the main reason for choosing a gap former for PM 4 was speed. PM 4 has seen its capacity soar from 330,000 tons/yr to 450,000 tons/yr of uncoated fine paper and base papers for coating as a result of the upgrade.

"High speed production for fine paper on speed levels around 1,500 m/min is possible [with the new equipment]," Hoppe says. With the PM's previous setup, speed levels above 1,250 m/min were not attainable. The other advantages lie in PM 4's improved paper quality and formation characteristics since it restarted in September last year, says Hoppe.

The main feature of Valmet's OptiFormer is that it has two different forming modules - a feature that enables the unit to be customized. The first is a loadable blade, while the second is a multi-foil shoe module (PPI February 1999, pg. 30). On top of the benefits of customization, Valmet also believes that the modular approach ensures that paper quality is maintained across all grades. The former also has more than enough drainage capacity to run at speeds in excess of 2,000 m/min, according to the supplier.

More recently, the Finnish supplier secured an order for a new paper machine in Germany that has a special twist in the forming area. The corrugated board producer, Prowell, has gone for a 275,000 ton/yr machine for its Propapier subsidiary in Magdeburg, Germany. Prowell is aiming big with its first foray into papermaking as PM 1 will be the world's fastest liner and fluting machine, according to Valmet.

Propapier’s new PM 1 layout

Operating speeds are set to reach up to 1,300 m/min, which is well above standard linerboard operating speeds of 900-1,000 m/min.

To reach such high speeds, the new PM is designed with several unique features, including a wet end composed of two gap formers. Although linerboard machines quite commonly have more than one former, they are usually based on the fourdrinier or single wire arrangement, rather than twin wire gap formers.

PM 1 will be the first machine in the world with a double gap former arrangement. A twin wire forming arrangement is needed to ensure high quality formation and to avoid disturbance to the sheet structure on the wire. As recycled fiber is harder to dewater than virgin fiber, the very high water drainage capacity of the twin wire formers is an additional benefit, according to Valmet.

Gaps to be filled

On top of liner grades, the gap former now appears to be well established for all paper grades, although there are still a number of improvements that could be made to the design. "The challenge now is to fine-tune the gap former for fine paper grades," according to Moser at Voith Sulzer.

Another area where suppliers will be concentrating their future research efforts is on the "free" headbox jet. As producers ramp up machine speeds, the free jet is becoming a cause for concern in terms of operational and sheet quality. As Moser explains, "With higher speeds and wider PMs, rolls are getting bigger, which in turns makes the free jet length very long. Jet surface roughness or turbulence becomes critical and the jet length needs to be minimized to maintain a smooth jet surface."

A number of research institutes and suppliers are working on this problem, but a solution is yet to be found. Going forward, suppliers will have their sights firmly set on this area as the problem is likely to hold back further speed increases to 3,000 m/min and beyond. But judging by the companies recent innovations in the forming area, it will not be long before they come up with an answer to this problem - a breakthrough that would leave papermakers free to shift up another gear in the forming section.

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