The paper manufacturer Hadera Paper produces wood-free copy and offset paper on the PM 4 in the Israeli city of Hadera. The replacement of the old former was carefully planned by Hadera Paper and Voith. During the development work, extensive tests were carried out by Voith on the pilot machine in Ravensburg, Germany.

The test results were convincing. The tests were done with an optimized DuoFormer D II. Thereby the formation was noticeably improved compared to the old former at Hadera and at the same time, with similar retention, the consumption of retention agent was noticeably reduced compared to a typically long pre-dewatering section. Even at speeds well above 800 m/min, good paper quality without faults and outstanding formation were obtained with the newly developed DuoFormer D II. The start-up of the DuoFormer D II in Hadera last fall confirmed the test results and confirmed the advantages of this trend-setting development. With the conversion of the former on the PM 4, the expectations are completely fulfilled. The formation is improved up to 15% due to conversion of the pre-dewatering section and the hybrid former to the DuoFormer D II.

The continuation of a 30-year success story. Use of the new DuoFormer D II in Hadera demonstrates that wood-free graphic paper can be produced with this former within a wide basis weight range with ideal product characteristics. The design of the pre-dewatering section, adapted for the respective end product, opens up many opportunities for applications within board, packaging paper and special paper operations along with applications for graphic grades.

The DuoFormer D II incorporated in two new board machines in China is in operations since last year. This is continuing the success story of the DuoFormer D from Voith. The latter was launched in 1984 and over 230 units are sold.

 

Focus on technology:

Voith DuoFormer D II with short pre-dewatering section

On the newly developed forming board, the low-pulsation initial sheet forming improves the retention from the beginning of the forming process. The combination of turbulence generation at the subsequent VacuFoil and control of the intake stock consistency for the DuoFormer D II with a wet suction box optimizes the further forming process.

The intake zone on the DuoFormer D II consists of three forming blades, which can be pneumatically loaded. They provide for a gentle merge of the top wire, suspension and Fourdrinier wire. The advantage is that the forming of the upper initial fiber mat is controlled in a targeted fashion by low dewatering pressures and individual settings of the intake strips compared to non-flexible and curved intake elements.

In the forming zone of the DuoFormer D II, pressure impulses provide an outstanding formation and symmetrical sheet structure in Z direction. The curved wire guide on the top wire suction box stabilizes the wire run. Application of the facing formation blades is thus determined solely by the technological requirements regarding formation. The functions are separated of wire guide and sheet forming, The number of formation blades used is depending on the basis weigh of the produced paper. Negative influences on the level of retention can thus be prevented., The dewatering is fast in the twin wire section producing low basis weights paper. The main forming zone is located around the blades at the very front end. The forming zone is extended into the back section of the forming strips when producing paper with high basis weight.