Do You Know The Function of Forming Board in Fourdrinier Paper Machine?

Forming board is the first component under the wire section behind the breast roll of foudrinier paper machine, which plays a role in supporting the forming fabric and controlling the amount of water removed from the wire section.

As the width of the paper machine increases, the diameter of the breast roll also increases. If the pulp flow is still near the centerline of the breast roll, there is a considerable distance between the landing point and the first table roll. If the speed of the paper machine is high, a large amount of dehydration will occur at the breast roll, which is suitable for some thin paper types, but for other paper machines, severe dehydration during initial forming is extremely detrimental to the formation of the paper sheet. It will make the fibers stand upright, affecting the strength of the resulting paper; It will cause a large amount of small fibers to leak, resulting in poor performance on both sides of the paper; Causing the initially deposited fiber layer to become too tight, which affects the smooth forming and dewatering of the pulp; It may even cause the forming fabric to sink at the breast roller, resulting in a jumping phenomenon on the mesh surface and affecting the formation of the paper web.

On modern high-speed fourdrinier paper machines, the forming board is usually a box composed of a wide flat beam and several small angle cutting plates . The landing point of the pulp flow is on the plane near the leading edge of the beam and slab. After the pulp flow is connected to the grid, the slow dehydration of the flat beam and slab can stabilize the pulp flow. Next is the cutting blade with a tilt angle of about 1 °, which is used to create low-intensity turbulence and appropriate dehydration to prevent fiber re aggregation.

The design and use of forming board are very important. To maintain a stable longitudinal flow velocity and prevent impact during the feeding process, the first step is to have a forming board that has been ground or flattened; Secondly, it is strictly ensured that it is parallel to the lip plate; Adjust the distance between them to eliminate the effect of backflow and recoil at the leading edge of the forming board; In addition, the leading edge of the forming board should be slightly inclined downwards to overcome the impact of the pulp when sprayed onto the mesh surface of the forming board, otherwise, the pulp will generate wave ridges on the forming board. If the forming board is much lower than the forming fabric, it will cause the water in the wire to recoil and damage the stability of the pulp. A typical tilted state of the forming board. The degree of inclination of the forming board depends on the specific situation.

The forming surface layer must be made of wear-resistant materials to reduce wear and damage to the forming fabric. Wear resistant materials that are not easily deformed, such as polytetrafluoroethylene, high-density polyethylene, ceramics, etc.

The forming board made of alumina sintered ceramic panel has good performance, it is very wear-resistant, has a smooth surface, and can be made into a straight and sharp leading edge to avoid pushing water back onto the mesh and damaging the initially deposited fiber layer. Sintered ceramics have no affinity with most resins and can be kept clean for a long time without sticking or clogging, with minimal maintenance work.