Forming, drying nets

Description

Nets for KDM and BDM are woven products that are made specifically for each part of a cardboard or paper machine with individual technical parameters.   These include:

-Forming grids;
-Pressed cloths;
-Drying nets.

The forming mesh is used in the area of sheet formation of the papermaking machine. Paper production at BDM begins in the forming part, where the previously prepared paper pulp is evenly distributed over the forming grid, which serves as a conveyor of the paper web and as a dehydrating element. It is in the forming part that the paper web is formed and the initial dehydration occurs. As the mesh moves, water is drained through it, while the fibers and fillers from which the web is formed remain on the surface.

FORMING NETS (FABRICS)

Forming meshes (fabrics) for a paper machine are made by weaving threads oriented in the machine direction (MD) and cross-machine direction (CD). There are many different weaving patterns, but they can be grouped into four general categories or styles depending on the number of layers of CD yarn.

Four styles of fabric:
	Single layer, one set of CD threads woven together with one set of MD threads. Double layer – two sets of CD threads stacked on top of each other, woven together with one set of MD threads.
Double-layered, two sets of CD filaments stacked on top of each other, woven together with one set of MD filaments, to enhance the abrasion resistance and fiber support properties
	Two and a half layers – two-layer forming fabrics have the disadvantage of a poor balance of dehydration efficiency and fiber support, so two-layer and half-layer fabrics come out. Additional CD filaments, usually smaller in diameter, are added to the top layer of the double-layered fabric to provide better fiber support, as well as expand the space and increase the dehydration ability and service life.
Although two-layer forming fabrics have good advantages, they are not impregnable, they do not maximize the characteristics of the upper and lower layer due to structural limitations, so three-layer ones appear on demand. Three–layer - two single-layer forming fabrics connected by a set of smaller CD strands to obtain much better anchor points. The surface layer is flat and heals, which has the best property for forming a sheet, the bottom layer is four, five or six heals to obtain good wear resistance

The main properties of forming grids

With the help of properly designed and maintained molding grids (fabrics), paper (cardboard) is produced that meets the specifications of the final product at an acceptable production speed. The variable designs and designs of paper forming grids affect the overall quality of the sheet. The main property of Forming grids is the following:

- dehydrating property expressed by the parameter of breathability and drainage index (DI). The pulp concentration is about 0.4% ~ 1%, that is, more than 99% of the pulp is water, and about 96% of the water is dehydrated in the molding area. The molding mesh must dehydrate a huge volume of water in a short period of time;

- fiber support capacity: expressed by the fiber support coefficient (FSI). Well-forming fabrics not only need to drain water quickly, but also need to support fibers on the surface to form a sheet. Good fiber support of the molding fabric improves the characteristics of the sheet, such as flatness, smoothness, printability and strength properties, and also avoids fiber embedding or clogging of the molding mesh, reduces the loss of fine fibers and fillers;

- mechanical properties: The mechanical property of the molding mesh includes:

   a) The possibility of transferring the sheet to the pressing section on a paper machine, as well as the ability to direct and drive the molding grid itself;

   b) Stability in the lateral part ensures good flatness of the sheet of the lateral part, and stability in the longitudinal part to increase efficiency and driving properties.

   c) Good rigidity, which will increase the throughput of the paper machine and efficiency;

   d) Excellent wear resistance makes the molding mesh with a long service life.

 

PRESSED CLOTHS

The press cloths are installed in the pressing part of the papermaking machine, which serves for the mechanical dewatering of the paper web after the grid table. In the pressing part of the paper machine, excess water is mechanically removed from the newly formed web. In presses, the cloth is transported by pressing cloth into the grip of a dewatering press between two shafts, where water is squeezed out of the paper cloth under high pressure.

DRYING NETS

In the drying part, the paper cloth passes between hot cylinders of large diameter, and moisture is removed by evaporation. Drying nets tightly press the cloth against the cylinders of the entire drying part. Drying nets are made of monofilament, must be powerful and heat-resistant, and must also have certain drying and running properties. Different papermaking machines, different types of paper, different pulp and different press locations have individual requirements for paper cloths, so our design concept is "an individual solution for each customer". BCmesh and our technical services will work with you to select and develop products that suit you. In the process of using the product, we receive feedback from the Buyer, analyze and resolve any issues that arise.

The main properties of drying nets

- The unique seamless spiral-bonded screen surface is ideal for the drying sector of marking-sensitive paper and applications where seam is unacceptable. Each spiral loop can be buttoned, the seam is identical to the body tissue itself. It is easy to install and repair to reduce downtime and increase the long service life of the seam to save costs, as it is well known that the joint is always a weakness of the contour belt.

- Compared with the fabric of the woven dryer, the spiral mesh belt dryer has greater breathability and drying efficiency. Permeability is the most important parameter of the drying cloth. Drying nets have greater air permeability than other dryer fabrics in the same working condition, this can help reduce the steam pressure in the drying cylinder or high speed at the same pressure. In addition, the special spiral design makes the dry fabric have a higher contact area to improve heat transfer. All this helps to increase the drying efficiency and save at least 10% of energy costs, which is more economical.

- The mesh drying tape has a smooth surface to get a smooth and non-surface marking sheet.

- Drying nets made of polyester yarn have excellent strength and wear resistance due to the unique design and strength of the superior PET material. It can withstand high tensile strength to make the sheet closer to the drying area, ensure uniform moistening of the sheet and shrinkage to obtain high-quality products.

BCmesh offers a wide range of spiral drying fabrics for each drying sector.

Depending on the diameter of the yarn and the size of the spiral ring, we have a small, medium and large loop. The larger loop uses thicker yarn to obtain superior tensile strength and ventilation, albeit a rough surface. And a small loop has a thinner yarn, less breathability and a thin surface.

The breathability is adjusted by inserting round or flat threads into the spiral ring to adapt different applications and drying.

Fabrics for the spiral loop of flat yarn are also available, its larger contact area with the sheet and lower permeability and caliper than the standard spiral, suitable for those cases where woven products may not work as desired.

FEATURES OF OUR PRODUCTS

- High resistance to deformation and wear resistance;

- Have the required breathability;

- Stable to heat and moisture;

- Have low heat shrinkage and longitudinal deformation at high temperature;

- New standards in the field of seamless and suture designs of pressed cloths;

- Wide range of designs and breathability of drying nets;

- Modern materials and technologies for weaving clothes for cars.