The key to future reeling technology can be found in the past
By Pulp & Paper Canada
By Pulp & Paper Canada
THE FUNDAMENTAL requirements for reels have remained virtually unchanged since the first reel was designed. Quality and quantity of the product reeled, safety, and reliability are still the major conc…
THE FUNDAMENTAL requirements for reels have remained virtually unchanged since the first reel was designed. Quality and quantity of the product reeled, safety, and reliability are still the major concerns.
The first complete papermaking machine was patented in 1799 and included a reel which consisted of simply a wind-up roll. The reel remained virtually unchanged for 120 years, reported Gerry Kramer, Beloit Corp. In his keynote presentation at the Thursday afternoon Reeling and Winding session, Kramer said that in the 1990’s reeling technology is getting back to the no transfers qualities of those original designs. “The second generation reels … in the 1990’s try to take steps back to the simplicity of the early reels,” he said. Increasing speeds and machine widths, however, make it more difficult to obtain those optimal reeling conditions.
Since the first nip on a reel resulted from reel design changes of the 1930’s, torque, nip and tension have been used to obtain the desired results.
Torque: Primary and secondary centrewind assist drives are becoming more common for many grades on modern reels. Increasing machine widths and speeds have encouraged the use of these drives.
Nip control: To relieve many of the winding defects such as creping, bursts and corrugations, technologies today focus on operating at low nip pressures. Again the simplicity of the first reel designs, without a nip, seems ideal.
Tension control: Continuous advances in sensor technology gauging strain and lightweight material for rolls have and will continue to control this variable.
A fully supported sheet is another aspect of the original design enjoying a renaissance. Turning away from the nip and eliminating the open draw areas is the challenge.
Despite the reeling advances with on-machine finishing, on-machine slitting, process automation and handling automation, Kramer said the in the last 200 years we have proved that the design of 1799 may have been ideal. For the design of the future, he said responding to a question from the audience, expect fewer moving parts and lower nip pressure.
Relieving nip pressure was a consideration in the $63 million project undertaken at Stora Enso in Grycksbo, Sweden. In 1996, the mill decided to increase the capacity of its PM 10 by increasing its speed from 840 to 1100 m/min. Increasing paper quality and roll structure was an additional goal, and the mill was also planning to reduce staff. “The winder would have been a bottleneck for the speed up,” said Jan Gronewald, Voith Sulzer Paper Technology, because of its limited speed of 1800 m/min and limited rewind roll diameter.
The two-drum winder had its restrictions, for one the pressure in the nips, but the mill asked Voith to develop something to stay with the existing two-drum winder format, yet relieve the pressure in the rolls.
A Voith TORO winder was installed and modifications were made “such as shoe presses, mechanical and electrical drives,” said Gronewald. The project also saw the elongation of the pre-drying section with six dryer cans, installation of two blade coaters and drying equipment, and new QCS and OP system.
The PM 10 winder rebuild was successful, allowing for up to 2500 m/min production speeds.
Traditionally with the two-drum winder, torque, nip and tension are the only tools available to get the hardness in the roll acceptable for a particular grade. Variable geometry, however, is the fourth winding tools, according to Todd Williams, Beloit Winders. “Just by moving the (pivoting) front drum at different speeds and times it was possible to vary the wound tension inside the roll by approximately 100%. That was without using any of the other (winding) tools,” Williams said.
The investigation found that when the drum is moved the role will move down into that pocket, with a decreased coefficient of friction. Moving the drum changes the nip intensity.
Variable geometry provides additional control to winding, while another study sought to quantify and provide a tool to decipher the various contacts and their effects.
Marko Jorkama, Valmet Corp., presented a model for the winding nip. He described centre-winding configuration. A model was developed to predict the tension out, “taking into account the points of contact that slip and those that stick,” Jorkama said.
All of these innovations strive to increase the quality and/or quantity of the paper produced. Often, however, “defects in the paper happen after the last set of winding,” said Kramer in his second presentation of the session. “None have to do with winding.” Some of the newer technologies decrease waste and increase uniformity throughout the role. The TNT, for example, differs from other rolls because of: a) spools that remain at the same elevation; b) a load controlled reel drum; c) uninterrupted centrewind torque control; and d) position controlled spool movement. According to Kramer, the reel concept winds high-quality jumbo rolls on paper machines manufacturing a wide range of grades.l