How Dryer Fabric Permeability Affects Packaging Paper Quality

The dryer fabric is no doubt a core part of the paper machine dryer section

For packaging paper of the same basis weight, some paper machines can stably achieve their design speeds, whereas others frequently encounter issues such as insufficient drying and high energy consumption.

A key factor contributing to this disparity is often the air permeability of the dryer fabric.

Dryer Fabric Permeability Selection for Different Drying Sections

Pre-Dryer Cylinder (Wet End) Dryer Fabric

In this zone, the paper web still contains a high amount of moisture and has relatively low wet strength, making it the most vulnerable stage in the drying process for sheet instability and runnability problems.

In this dryer zone, dryer fabric with low air permeability is typically selected.

High Dryer Fabric Permeability

When the air permeability of the dryer fabric in this zone is excessively high, air penetration becomes excessive.

• The wet paper sheet will finally fail to adhere tightly to the fabric surface during high-speed machine operation, making the package paper web highly prone to edge fluttering and overall sheet instability. This, in turn, leads to issues such as paper breaks and surface wrinkling.
• At the same time, the strong airflow through the high air permeability dryer fabric scours the fibers and fillers on the paper surface. This results in noticeable wire marks and pinholes on the paper sheet, making its surface rougher and creating potential issues for the subsequent calendering and rewinding processes. On the other hand, the intensified shedding of fibers and dust caused by high-velocity airflow scouring makes the openings of the dryer fabric prone to clogging with these impurities, thereby shortening its service life.

• Furthermore, excessively high air permeability will cause hot air pass through the dryer fabric too rapidly, preventing a portion of the heat from effectively acting on the paper sheet and reducing the thermal energy utilization efficiency of the dryer section.
• This results in reduced pre-dewatering efficiency at the inlet section of the dryer cylinder, increases the subsequent drying load, and leads to excessive steam consumption.

Moderate Dryer Fabric Permeability

When the air permeability of the dryer fabric is within a reasonable range, the airflow can smoothly penetrate the wire, keeping the wet paper sheet stably attached to the fabric surface, thereby improving the stability of the package paper web and reducing problems such as paper web drift, paper breakage, and wrinkles that occur during high-speed production.

At the same time, a moderate airflow penetration velocity allows the hot air to maintain an optimal contact duration between the paper sheet and the dryer fabric, thereby enhancing heat transfer efficiency, stabilizing the pre-dewatering process, and helping to reduce energy consumption during production.

Under these conditions, since the airflow does not exert excessive scouring force on the paper surface, the paper retains shallower wire marks and exhibits reduced fiber shedding and dusting during the forming process, thereby achieving superior surface quality.

Intermediate Dryer Cylinder (Transition Drying Zone) Dryer Fabric

Following initial dewatering, the moisture content of the package paper sheet drops rapidly, and the dry strength of the wet sheet gradually increases.

This area is responsible for the main moisture removal task of the entire paper machine, so it needs to balance dewatering efficiency and paper web running stability.

At this stage, the use of dryer fabrics with medium permeability is recommended.

As the paper gradually dries in the dryer cylinder group, you can gradually and slightly increase the air permeability of the dryer fabric along the direction of the dryer cylinder group according to the actual operation of the dryer section, so that water vapor can be discharged more smoothly.

For this reason, this area typically exhibits the highest air permeability of the dryer fabric across the entire paper machine.

Low Dryer Fabric Permeability

At this stage, low dryer fabric permeability restricts the pathways for vapor and water drainage, preventing the timely escape of evaporated moisture from the paper sheet. 

• This leads to the formation of a water film on the dryer cylinder surface, directly causing issues such as sheet sticking, black spots, and pulp scabs.
• Using a dryer fabric with low air permeability may also impede the lateral flow of water vapor, leading to increased moisture variation across the paper web. 
• This makes the finished product highly prone to subsequent warping, thereby affecting its performance during corrugated board processing and use.
• As for the dryer fabric itself, the long-term accumulation of moisture can lead to internal scaling and pulp buildup, thereby accelerating the fabric’s aging and deterioration.

High Dryer Fabric Permeability

Using highly permeable dryer fabrics causes the paper’s moisture to be removed too rapidly, making the removal of moisture from the surface layers and the interior unsynchronized, creating a significant moisture gradient and leading to the accumulation of residual stress within the package paper web.

Furthermore, if the paper sheet dries too rapidly in localized areas, uneven fiber shrinkage occurs, reducing the paper’s toughness and adversely affecting physical properties such as folding endurance and bursting strength.

Rear-Section Dryer Cylinder Group (Finished Product Drying Zone)

At this stage, the moisture content of the paper is close to the finished product standard, and the drying rate needs to be gradually reduced to ensure the stability of the paper structure.

Therefore, dryer fabric with low to medium permeability is typically selected for the final drying section to prevent excessively rapid moisture removal from affecting paper quality.

High Dryer Fabric Permeability

When the air permeability of the dryer fabric used is relatively high, excessive ventilation through the fabric causes the paper sheet to undergo additional drying.

• This results in the paper sheet having a moisture content below the process standards for wrapping paper.
• Causes increased paper brittleness and exacerbates static electricity issues.
• Reduce the frequency of web breaks during the rewinding and slitting processes.
• Meanwhile, prolonged exposure to high temperature and high air volume environments caused by high air permeability dryer fabric can easily affect the fiber structure of package paper sheets, leading to a decrease in key physical indicators such as ring crush strength and bursting strength, thus reducing the overall performance of packaging paper.
• In addition, excessively rapid surface drying may cause uneven moisture distribution in the paper, resulting in an overly dry surface and high internal moisture content, making the finished packaging paper more prone to problems such as re-moistening, warping, and decreased dimensional stability during storage.

Moderate Dryer Fabric Permeability

Appropriate dryer fabric permeability ensures the paper undergoes a balanced drying process, allowing its moisture content to decrease gradually and uniformly. This prevents localized over-drying and results in stable physical properties that meet process specifications.

This results in low static electricity in the paper sheet, ensuring smooth operation during rewinding and slitting, and keeping the rate of paper breaks within a controllable range.

At the same time, a well-designed dryer fabric air permeability can reduce internal paper stress and improve web flatness and dimensional stability, thereby enhancing the packaging paper’s processability on downstream corrugated production lines.