Dryer Fabric Selection and Installation and Precautions for Paper Defects

The selection and installation of the dryer fabric is far more than a simple replacement of consumables. Its performance and condition constantly affect the paper’s flatness, strength, and other physical properties, as well as the efficiency of the production line. Incorrect selection and installation can lead to wire marks, creases, and increased energy consumption in the drying section, resulting in unplanned equipment downtime. Therefore, the scientific selection and standardized installation of polyester drying wire are crucial.

Key Performance Parameters for the Dryer Fabric

Air permeability: As a core parameter, it directly affects drying efficiency and energy consumption. Low basis weight paper can use high-permeability dryer fabrics to quickly expel large amounts of steam. High basis weight paper can use medium-low permeability wires to prevent excessive paper adhesion to the wire, surface roughness, and ensure strength.
Yarn material: monofilament is more wear-resistant, flat yarn has better contact with the paper surface, and PPS material can meet the high temperature hydrolysis requirements of the drying section, ensuring the strength and service life of the dryer fabric under high humidity and high temperature conditions.

(3) Interface type: According to the customer’s needs for polyester dryer fabric, spiral interface, pin ring interface, ring interface, plug-in spiral ring interface, etc. can be provided.

How to Properly Install Polyester Dryer Fabric?

When installing the dryer fabric, pay attention to the environment. It should be clean, tidy, and free of pollution. Avoid dragging the dryer fabric on the ground to prevent snagging and wear. The installation direction should follow the wire’s running direction. Most importantly, after installation, it must be run at low speed with low tension, then gradually increase the speed and tension until normal. (Do not directly tension to normal tension all at once; excessive stress and stretching can cause the dryer fabric to break.)

In paper production, paper defects in the drying section of the paper machine are relatively rare. Common defects include water droplets and dryer fabric marks. Paper defects caused by defects in the dryer fabric, resulting in material carryover, creases and bulges caused by the sizing machine, and drying creases.

The drying section mainly removes bound water from the paper sheet through evaporation. During this process, the paper’s dryness will change from about 40% to over 90%. The paper sheet will shrink slightly, but its strength will also increase.

To Address Paper Defects Caused By Dryer Fabric, the Following Points Should be Noted

The moisture evaporated from the paper should be removed in time, otherwise it will condense and cause water droplets. The black water droplets and dryer fabric marks are all related to this.
On the BM2 single hanging wire, some impurities often stick to the paper due to improper wet section chemistry of the paper machine, which will cause defects on the surface of the paper and lead to material carrying after coating. Some drying cylinders do not have doctor blades, and the surfaces of these cylinders often have foreign matter adhering to them. Sometimes, after paper feeding, large pieces of paper remain on the doctor blade of the drying cylinder. These paper pieces can also scratch the paper surface, causing material carryover on the soft calender roll.
Polyester dryer fabric has a certain service life. It is also a consumable item that needs to be replaced regularly. Otherwise, the aging of the dryer fabric will affect the operation of the paper machine. When dealing with paper entanglement in the drying cylinder and other issues, care should be taken to protect the dryer fabric, as a damaged dryer fabric can also damage the paper.
A key point to note during surface sizing is the drying process, which generally results in three types of paper defects: dead folds, live folds, and raised/lowered streaks. Dead folds are caused by uneven pressure between the two sizing rollers; live folds are caused by internal defects in the paper, such as uneven moisture content, uneven basis weight, speed differences between guide rollers, and improper use of the spreading roller, especially noticeable with low basis weight paper. Raised/lowered streaks are caused by uneven sizing in certain areas, generally related to the use of the metering rod and the presence of foreign matter in the system. (5) When hard calendering, pay attention to the following: The most common paper defect in hard calendering is indentation, but indentation often appears on the soft calendering roller, causing continuous material carrying on the upper or lower roller of the soft calendering. If there is a problem with the roller surface in hard calendering, for example, due to the local difference in roller diameter, it will also be reflected in the paper thickness deviation.