Dynaflo-C2 is a hydraulic headbox specially conceived for Crescent formers on two-layers tissue grades, at speeds from 1,000 to 2,500 mpm and basis weight from 10 to 40 gsm. An excellent stock dispersion is guaranteed by the exclusive Dynaflo tubes, the turbulence generating device at the basis of OVER's modern hydraulic headbox design.
The Dynaflo concept is the result of extensive researches carried out since the late '70's on the OVER's pilot plant. The flow coming from the tapered headers passes through a separated mixing/equalizing chamber that optimizes the stock pressure and fiber suspension just before the turbulence generator of each layer.
The turbulence generators are the core of the DYNAFLO concept: the stainless steel Dynaflo tubes present a conical cross section, transitioning gradually from round to rectangular.
After a high acceleration at the inlet orifice, a gradual diffusion of the stock flow along the Dynaflo tubes weakens the large-scale turbulence, while sustaining small-scale turbulence, thanks to the many boundary layers generated by the friction with the tube walls. Each tubes row has an optimum velocity range: by multiplying the tubes rows, a broad range of flow rates can be accommodated, giving this headbox design the greatest adaptability to all operating conditions. The configuration of the tubes row ensures a negligible residual wake signature on the stock jet. This concept, after 30 years from its birth, still gives one of the best sheet formation made on today's hydraulic headboxes.
The headbox is supplied with stiff lamellas in the slice area. They maintain high the level of micro-turbulence up to the jet exit, improving paper formation at high speeds. Special lamellas' tip design is performed to avoid the wake effect in the slice flow.
The beak-like nozzle allows a minimal free jet length, essential for good performances at the highest operating speeds. The design of this headbox alloes a complete separation of the two layers, ensuring a purity better than 90%. Its entire construction in solid 316 L stainless steel, with thorough finish and electropolishing of all the surfaces in contact with the stock, will guarantee safe and trouble-free operations for many years. The CD profiling is made either manually or automatically, QCS driven, by micro-screw jacks spaced 150 mm, or optionally 100 mm. The dilution profiling of one of the two layers is also available through QCS control.