What Causes Forming Fabric Breakage During Paper Making?

In paper making, the forming fabric is a core component of the wet end of the paper machine, playing a crucial role in dewatering, paper formation, and transport. The quality and performance of the forming fabric significantly impact paper quality, production efficiency, and costs. However, common problems encountered during production include clogging, wear, and corrosion of the forming fabric. Below, Sun Hong will explain to you some of the problems and solutions faced by forming fabrics in paper making production.

Forming Fabric Wear Problems and Solutions

The primary cause of forming fabric downtime is wear, accounting for up to 70% of failures. Wear can be categorized into three types:

• Localized wear at the edge of the forming fabric
  Frequent wear occurs approximately 10-13cm from the edge of the forming fabric, concentrated at the transition zone of the vacuum box cover. This is mainly caused by sharp edges or gaps in the vacuum box cover panel joints and insufficient lubrication at the ceramic panel joints.
  Solution: Keep the needle nozzles of the normal pressure lubrication water system on the edge of the vacuum box cover unblocked to reduce frictional heat accumulation. Regularly check the joints of the wiper blades and ceramic Forming Board, grind the edges and fill the gaps. Restore roller surface uniformity; repair worn guide rollers with a rubber coating.
• Rapid overall wear of the forming fabric
  Uniform wear across the entire width is mainly caused by poor tension control and low-quality filler material. When the tension of a single-layer forming mesh is lower than 3kg/cm and that of a double-layer forming mesh is lower than 5kg/cm, the friction between the mesh and the guide roller will intensify, and inferior fillers will directly abrade the mesh wire.
  Solution: Ensure that the tension value is stable at the process upper limit; filter the filler through 200 mesh to remove hard debris; optimize the air permeability of the forming mesh to avoid “adsorption wear” under high vacuum.
• Longitudinal wrinkling or general wear
  Misalignment of the forming board or suction box cover plate, or unevenness of the vacuum box cover panel can cause hard longitudinal wrinkles, leading to continuous wrinkling and premature replacement of the forming fabric.
  Solution: Use a laser alignment tool to check the flatness of the dewatering elements, maintaining a tolerance of approximately 0.1mm. The vacuum box cover is made of self-lubricating material to reduce friction.

Operational Fault Diagnosis and Correction

During high-speed operation, the forming fabric can easily lose its dynamic balance, leading to reduced dewatering efficiency or even mesh breakage. The following are common faults:

• Pulp accumulation on the guide roll
  Fibers accumulate on the guide roll surface, blocking the dewatering channels. The direct cause is insufficient high-pressure water pressure or nozzle clogging, leading to fibers embedding in the mesh pores.
  Solution: Maintain the pressure between 1.0-3.0 MPa and rinse repeatedly.
• Vacuum box cover top slurry Slurry splashes from the gap of the vacuum box cover, causing fiber loss and uneven quantitative. The main causes are a mismatch between the mesh permeability and pulp characteristics (e.g., short fibers with high permeability mesh) or insufficient retention aid addition.
  Solution: Use low permeability mesh for short fiber pulp, optimize retention aid addition point, and use dual-component retention.

Chemical and Mechanical Damage Prevention

Chemical corrosion and cleaning damage to the forming fabric cannot be ignored, as it significantly affects the mesh lifespan.

• Improper chemical cleaning: Polyamide (nylon) weft mesh will become brittle and break when exposed to strong acid (pH < 3), and the forming fabric will delaminate and disintegrate when exposed to strong alkali (PH > 12) for a long time.
  Solution: Implement a pH classification system for cleaning agents. Use only neutral enzyme-based agents (pH 6-8) for nylon mesh; weak alkaline agents (pH<=10) can be used for polyester mesh. Limit chemical immersion time to 2 hours to avoid molecular chain degradation.
• High-pressure water washing damage
  When the pressure is greate than 3.0 MPa and the washing is continued for 30 minutes, the polyester monofilaments of the forming fabric will become fluffy and rupture. If the needle nozzle distance is less than 100 mm, it will directly cause cutting damage to the forming fabric.