State-of-the-art conditions for dewatering

3 Products for the Suction Pressure Roll

2015-06-10 - The demand on the suction roll nip of a tissue machine is daunting: it is required to provide the best possible and consistent dewatering, on-spec tissue quality with the lowest CD moisture profile deviation from start-up to felt change, all at the lowest possible energy consumption. Using state-of-the-art technology these demands are being better fulfilled than ever before. The combination of an innovative sealing strip system within the suction pressure roll, a polyurethane roll cover on suction and press roll shells and the latest generation of high performance press felts is breaking new ground in performance. Starting from inside the roll and moving out, Voith presents the trio of HydroSeal, SolarSoft and Evolution.

HydroSeal is a sealing strip system for all suction roll types. Within the tissue sector it has proven to deliver results. An impressive impact on operating costs was achieved through an 87% reduction of sealing strip lubrication water consumption, an increase in the operating felt temperature by 5°C, a reduction of the electrical drive power by over 2% and an extension of the running intervals. All of these results have made for an exciting return on investment. The investment itself can be kept within reasonable limits as HydroSeal can be retrofitted to an existing roll within the scope of a regular roll service.
How HydroSeal works HydroSeal is a revolutionized sealing strip system with an integrated lubrication water feed from within each seal. What makes it special is that the water needed for lubrication is distributed uniformly over the entire width of the sealing strip. A film of lubrication water without back-splash is created between the sealing strip and the roll shell inside diameter. This unique water feed substantially reduces the amount of lubricating water required when compared to a conventional and typical shower bar system with spray nozzles that are prone to blocking and interrupting the supply of needed water.
The well-known tissue manufacturers Hakle Reisholz & Wepa Mainz in Germany and Kimberly-Clark Coleshill in the UK have installed HydroSeal. They report savings of up to 30,000 m³ of water per year with HydroSeal. The reduced amount of water in the nip reduces over-saturation of the paper web, contributing to an improved CD moisture profile. The bigger contributor to the success of HydroSeal remains a productivity increase. Each reference installation was able to achieve up to 30m/min higher machine speed or a reduction of the net energy input / ton through a combination of electrical, gas and steam consumption at existing machine speed.
Through deeper and parallel grooves, SolarSoft has an increased void of volume and an improved water-handling capacity.
SolarSoft polyurethane roll covers are specially designed for pressure and suction pressure rolls. The stability of the functional layer allows more freedom in the choice of surface design and open area. Grooves that are deeper and parallel make an increase of void volume possible, directly improving water-handling capacity. Hardness stability and hydrolysis resistance combat wear while the combination of deeper grooves and wear resistance allows for longer grinding intervals. The successful application of a SolarSoft cover requires a careful study to be made of the nip condition through nip impressions, on-the-run Yankee diagnostics and crown adaptation know-how, all available from Voith. The reference list shows that SolarSoft sets new standards in high performance pressure roll covers.
Evolution press felts are thinner and lighter than industry typical designs, the practical benefit making it easier to ply and install on the machine.
The distinguishing feature of Evolution press felts is the polymer film integrated into selective positions of the felt sub-structure. The felt is thinner and lighter than industry typical designs, the practical benefit making it easier to ply and install on the machine. By design and due to the manufacturing process the felt has a higher density, reaching target operating density and maximum machine speed faster. A reduction in energy, by shutting off a vacuum pump has been realized as the dewatering efficiency of the press fabric alleviates the need for higher vacuum. The biggest contributor to the success of Evolution however is the dewatering performance. The design targets nip dewatering, the dry content increase after the press leads to higher machine speeds, alternatively lower net energy input / ton. The polymer layer acts as a barrier to contamination of the base weave giving the fabric an outstanding response to cleaning.
With HydroSeal, Solarsoft and Evolution Voith has taken a leading role in reducing consumption of resources thereby reducing costs / ton or alternatively increasing machine output while improving sheet quality.//