Dynaflo-C is a hydraulic headbox specially conceived for tissue Crescent formers at very high speeds, up to 2,400 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 the OVER's modern hydraulic headbox design. The beak-like nozzle allows a minimal free jet length, essential for good performances at the highest operating speeds.
The Dynaflo concept is the result of extensive researches carried out since the late '70's on OVER's pilot plant. The flow coming from the computer designed tapered header passes through a first perforated plate into a mixing/equalizing chamber that optimizes the stock pressure and fiber suspension just before the turbulence generator, which is 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 the 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 row, a great 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 can be supplied with stiff lamellas in the slice area in the model DYNAFLO-C; 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.
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 a safe and trouble-free operation for many years. The CD profiling is realized either manually or automatically, QCS driven, by micro-screw jacks spaced 150 mm, or optionally 100 mm. The dilution profiling is also available through QCS control.