The Influence of Sticking Net on Forming Fabric

In paper making, a common and troublesome phenomenon is “sticking net.” This refers to the blockage of the openings on the forming fabric, preventing water filtration. It severely impacts paper forming and dewatering, significantly affecting even normal paper making. This phenomenon occurs when, after the pulp adheres to the forming fabric, the pulp around the blockage is first filtered and set, resulting in a thinner pulp layer. The pulp then flows outwards, creating a thin pulp area or a pulp-free area, which eventually becomes a hole on the finished paper.

Common types include small, star-shaped white dots (each blocking an opening), as well as strips 20-30 mm wide, approximately the width of several openings. Additionally, there are also horizontal strips of considerable width and density formed by these star-shaped white dots behind the forming fabric joints.

Substances That Cause Blocked of Forming Fabric

• A mixture of fine fibers and non-fibrous characteristics. For example, when calcium carbonate is used as a filler, the mixture of yellow, sticky calcium carbonate and fine fibers can cause the forming fabric to become blocked.
• Another possibility is excessively high temperatures. In hot summer weather, rosin with high free content is prone to clumping and blocked of the pores.
• Resin blocks: When using slurry with a high resin content, resin blocks often condense and stick to the surface of the forming fabric.
• Paper machines using waste paper pulp as raw material may also produce asphalt lumps, wax spots, oil stains, rubber lumps, paint spots, etc.

Handling Blocked of Forming Fabric

For non-resin-related issues

• When blocked occurs, do not adjust the vacuum level of the vacuum suction box too high; a slightly lower level than normal is sufficient. If lowering the total vacuum level causes excessive moisture in the wet paper sheet, affecting normal paper making production, you can reduce the vacuum level of only the first and second vacuum boxes.
• Properly tensioning the forming fabric can effectively eliminate blocked at pits, creases, and blockage mesh joints.
• Strengthen washing during the return stroke of the forming fabric, especially the swing high pressure cleaning water system should be normal and the pressure should reach 20-25 kg/m².
• When blocked is detected, Clean foam from the front box promptly. The foam often contains alcohol and benzene extracts, which, when attached to the forming fabric along with the pulp, can cause blocked of the mesh.
• In addition, the freeness of rosin material should be appropriately reduced in the high temperature of summer, and the dissolution and addition process of calcium carbonate should be reasonably controlled to prevent the formation of yellow sticky substances, which helps to solve the blockage phenomenon.

Treatment of resin-related issues

• The most basic measure is to control the resin content in the pulp.
• Use alum to control the resin content and to properly control the pH value.
• Strengthen cleaning management and regularly clean pipes, pulpers, storage tanks, and various pulp troughs to prevent excessive resin accumulation and mixing into the pulp.
• Use resin dispersants and fixatives to disperse and remove the resin.

When using waste paper as raw material, it is important to strengthen the processing to prevent impurities such as asphalt and plastic from being mixed in

• Generally, steam cleaning can be used. For asphalt, rubber blocks, oil stains, and paint, gasoline or kerosene can be used for cleaning. Under normal circumstances, do not treat the forming fabric with acid, as the mesh will become rough and uneven after acid corrosion, making it very easy for fibers to get caught, leading to more serious blockages.
• Sometimes, the blockage is caused by small fibers, resin, calcium sulfate precipitates, etc. sticking together. In this case, acid, alkali, and benzene will not clean it. Treatment with a copper ammonia solution can dissolve the small fibers and has a good effect.
• After treatment, be sure to rinse with plenty of clean water to prevent corrosion of the forming fabric.