Valmet’s novel gap forming technology OptiFormer Gap utilizes innovative shoe and blade technology to gain superior paper quality. This new concept has been studied extensively on the pilot machine scale, and results from several running production machines compare very well with the pilot results. The formation has beaten all other references.
Initial dewatering of OptiFormer Gap takes place under non-pulsating conditions utilizing Valmet’s VacuShoe technology. Water is removed in the VacuShoe chamber area (jet landing area) through both the inner and outer fabric producing good retention and symmetric filler distribution at high filler contents in the paper. This very gentle initial dewatering of shoe and blade technology with stabilized jet impingement and minimized free jet length enables an exceptionally wide operating window.
Non-optimized headbox slice geometry (left) versus optimized headbox slice geometry with OptiFlo Gap headbox (right).
After the paper surfaces have been formed, the dewatering continues in the blade dewatering phase, where the loading elements generate pressure pulses and shear forces inside the sheet. This finalizes the excellent formation and high dewatering capacity.
Dry content after the forming section ranges from 22% to 25%. This sufficiently high dry content after the forming section secures good runnability of the sheet at following process stages, e.g. dewatering control at the 1st press nip.
OptiFormer Gap with shoe and blade technology provides excellent end-product quality. A formation comparison (based on production machine data) of different forming methods. Grade: fine paper. Speed over 1800 m/min.
Forming section with shoe and blade technology can be operated with a variety of grades without having to readjust the forming parameters. A shoe and blade technology allows completely free adjustment of the slice opening, jet/wire ratio, and the jet landing point without causing any sheet disturbances.
OptiFormer Gap with shoe and blade technology ensures excellent runnability through improved cleanliness in the gap area. Unlike the traditional forming section with a forming roll, possible dirt particles are trapped between the fabric and closed roll, but because dewatering happens in the stationary shoe area, dewatering removes dirt from the fabric surface causing no light spots on the paper. Closed breast roll surface also reduces the amount of misting around the headbox slice area. Therefore the top and bottom slice areas are very clean and dry.
Key components of OptiFormer Gap with shoe and blade technology. OptiFormer Gap with shoe and blade technology is well suited also for rebuilds.
The video displays the shoe and blade technology in Valmet forming sections with both paper and packaging grade applications. In addition, we show multiple different forming section layout options where shoe and blade technology has been used.
Sappi's Gratkorn mill rebuilt their PM11 to improve the printing paper quality. The rebuild concept was optimized for improved formation and printability and reduced two-sidedness and validated in the series of pilot trials at Valmet facilities.
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