A Versatile System For Paper-Making In the Laboratory.
An instrument which produces test sheets with the similar properties and fibre orientation as paper made on full-size machines.
A Dynamic Sheet Former (DSF) provides the means of making large hand-sheets of paper and board, which are then used for research into paper properties, grade development and comprehensive testing of paper quality.The test results permit optimization of the pulp before it is introduced to the full size production paper machine.The instrument is constructed around a centrifuge drum with a forming fabric (wire) spread about its interior surface.During operation, water introduced into the spinning centrifuge builds up a wall until the wire is completely submerged. A traversing nozzle then sprays stock against the fabric to build up a fibre layer. When the required amount of stock has been deposited, the white water is removed, thus forming a wet paper web on the wire.
Desired physical, optical and printing properties of test sheets can be obtained by varying the grammage, MD/CD fibre orientation and the distribution of fibre and filler in the Z-direction. Test sheet properties can also be affected by the addition of chemicals to the furnish stream or in the stock holding tank.
CANPA Auto Dynamic Sheet Former (ADSF).
During sheet making, the delivery of an exact stock volume at a specific flow rate is ensured by the use of precision controlled pump with feedback from a magnetic flow-meter. The centrifuge, stock-nozzle and dewatering mechanisms are operated by electronically controlled servo and stepper motors to achieve accurate positioning. The machine’s ability to maintain tight control over the sheet forming process ensures a high repeatability of sheet properties. A multi-stock storage and control system increases the instrument’s versatility. All surfaces in contact with the furnish are made of stainless steel and chemically resistant materials. Full-flow valves are used throughout the machine to reduce the possibility of fibre damage and stock blockage.
Many new design features of the CANPA ADSF result in production of test sheets of superior uniformity and overall quality.
Unique and Advanced Features:
Completely digital control for precise, consistent results.Automatic sheet-making cycle increases operator productivity.Automatic multi-layer sheet production and white water collection. Three on-board 50 Litre tanks with agitation systems.One 10 Litre tank with vigorous stock agitation, attached to the machine. The nozzle tube remains secured to the extender mechanism during sheet removal. To achieve ultimate control over sheet uniformity, it is essential that the sheet remain undisturbed during formation and dewatering. The advanced design and precisely machined components of the ADSF are combined to produce an instrument virtually vibration-free. An additional benefit of this is the remarkably quiet operation of the machine. The versatility of the ADSF is achieved through software re-configuration of the machine’s operating modes. The sheet making cycle of the ADSF follows a program in the instruments computer. Simple menu-based prompts on control panel’s display allow the user to change the program parameters. By selecting menu options, the operator can set the desired water wall thickness, dewatering speed,dewatering mode, compacting speed, select white water collection, etc. The main menu on the display contains the basic parameters of the sheet-making cycle: selection of tank containing the stock, wire speed, stock volume per sheet,stock flow rate, dewatering speed. For multi-layered sheets,the tank holding the stock for each layer is specified. By editing parameters identified by the cursor, operator can adjust the machine’s working conditions.
Three other menus allow control of circulating pumps and the parameters, which are less frequently changed.With a touch of the START button, the operator initiates the automatic sheet-forming cycle: the spin and build-up of the water wall, stock spraying, then dewatering and compacting of the wet sheet. The automatic operation ensures high repeatability of formed sheets properties.Machine operation can be achieved manually as well,through the buttons on the control panel.
Each button has an associated status lamp and the activated functions operate according to values set in the menu.On the right side of operator’s panel is a simplified hydraulic schematic of the ADSF with colour-coded buttons, through which operator controls valves for distribution of liquids within the machine. The stock tanks of the machine are named as Tank-1 to Tank-4 for their identification to the program. The large capacity of the tanks together with the automatic operation of ADSF can actually be used for a micro-production of paper!When ADSF operates in white water collection mode, the indicator in the centre of the panel is illuminated. All whitewater, which is scooped during dewatering is then directed to the outlet in tank-1. It is later used from there for build up the water wall, while water, which is used for cleaning of the centrifuge is drained. To prevent flocculation, the stock in each tank is constantly circulated though agitation chambers, which have transparent walls and are prominently mounted on the front of the control box. Paddle mixers in the tanks provide additional agitation. Stock in each tank can’t be mixed with the stock in other tanks; it is selected for spraying by opening a valve in the manifold behind the mixing chambers.Multi layered sheets can be made from any combination of stocks in the tanks. The attached 10-litre tank-4 has its own circulation pump,which provides vigorous mixing of the pulp. It is convenient for making of a single sheet with added chemicals and fillers, or when a limited quantity of pulp is available. Tank-4is fully integrated in the machine program.A definite jet/wire ratio is obtained by setting program parameters for the wire speed and stock flow rate. By adjusting the position and spraying angle of the stock nozzle with respect to the forming fabric, the operator controls the stock impact angle to modify the fibre orientation in the paper sheets. The swing-out design of the stock nozzle holder allows easy removal of the sheet. To achieve high repeatability of sheet properties, it is important that the stock projection set-up of the machine remain constant. Once returned to the set position, the nozzle locks in place to resume its previous stock projection geometry.
Benefiting from more than THIRTY years experience with building dynamic sheet formers, CANPA has produced a rugged, reliable machine, which requires minimal maintenance. The modular design allows easy replacement of various machine components.
Wire speed during sheet making: 700 to 1900 m/minStock flow volume: 0.3 to 4.4 litres/minThree 50-liter stock tanks, on-boardOne 10-liter stock tank, attached to the machineAutomatic collection and reuse of white waterComputerized control with simple entry of operatingparametersElectrical: 200 to 240 Volts ac, 20 Amps, 50/60HzCompressed air: 550 kPa (80 PSI)Utility water and drainage.Dimension: 125 cm x 125 cm x 85 cmWeight: 400 kgPulp consistency: 0.05-2.0%Sheet size: 250mm x 970mmSheet basis weight range: 10-400 g/m2Wet sheet dryness: 20%CD/MD fibre orientation ratio: 0.2 to 0.9Fibre retention: approx. 95%
• Many new design features of the CANPA ADSF result in production of test sheets of superior uniformity and overall quality •