What is Press Felt?

What is Press Felt?

Paper making press felt is made of high strength synthetic fibers through needle punching and weaving processes. The surface is densely covered with micropores. It has the functions of dehydration, paper web transfer, and paper flattening. It is an important dehydration equipment in the press section of the paper machine. The quality of the press felt determines the quality and production efficiency of the paper.

How Does The Press Felt Work on The Paper Machine?

The wet paper sheets will be transferred from the forming section to the press section. The press felt will absorb the paper sheets through the micropores on the surface to avoid paper breakage or wrinkles, and ensure the stable transmission of the paper sheets. Then the paper sheets and the press felt pass through the press rollers together, and are mechanically squeezed to remove moisture (if some paper machines are equipped with vacuum water suction boxes after pressing, the excess moisture in the press felt can be further extracted to further improve the dryness of the paper sheets). Then the press felt carries the dehydrated paper sheets from the press section to the drying section. This process requires uniform tension to prevent the paper sheets from wrinkling and deflection. At the end of the press felt, the paper sheets smoothly transition to the drying cylinder of the drying section through the paper guide rope to complete the pressing and dehydration process.

How to Choose Suitable Press Felt for Paper Machine?

Choosing a suitable press felt requires considering multiple factors. Different types of paper machines have different requirements for press felt (for example, high-speed paper machines generally require press felt with high water permeability and high wear resistance to cope with the pressure and high temperature generated during high-speed operation). The type of paper produced, the speed of the machine, the gram weight, etc. should also be considered.

What Need to Know When Installing Press Felt for The First Time

(1) Make sure the press felt is installed in the correct direction. There is a felt number and a direction arrow on the front of the press felt. The direction arrow points to the direction of operation.

(2) Check the press felt tension. Too loose or too tight tension will affect the service life of the felt. A press felt with too loose tension will cause deviation and poor dehydration effect. Too tight tension will increase the friction coefficient and even damage the press felt or other equipment. Moderate press felt tension can ensure the stability and formation of paper.

(3) When the press felt is installed on the paper machine for the first time, it should not be operated at high speed, otherwise the high speed will cause damage to the felt surface, thereby affecting production stability and reducing the service life of the felt. The speed of the paper machine should be gradually increased to allow the press felt to adapt sufficiently.

Common Problems with Press Felts in Daily Production

(1) Press felt deviation: If the press felt is not kept on the correct track during production, it will cause paper wrinkles, breaks and unevenness.

Solution: This phenomenon needs to be checked step by step to ensure that the installation positions of both ends of the press felt are correct, avoid being too loose or too tight, and adjust the tension of the press felt to make it uniform. Regularly check the various parts of the paper machine to ensure that the press felt is not affected by deflection during operation. Check whether the guide roller is offset. If the guide roller is offset, it may also cause the press felt to deviate. It is also necessary to regularly check and adjust the guide roller position.

(2) Press felt surface wear: Excessive wear on the felt surface is usually caused by long-term high-speed operation and friction, which may cause the press felt to break.

Solution: Regularly handle impurities on the press felt surface and regularly check the wear condition, especially the contact parts such as the press roller and the drying roller to see if there is local wear. If local wear is found, it should be replaced in time.

(3) Poor dehydration of the press felt: The humidity of the paper is too high, and the production efficiency is reduced, affecting the production quality of subsequent processes.

Solution: Check the water permeability of the press felt. Impurities may have accumulated on the surface of the felt, which affects the water discharge. Clean it in time. It may also be that the press felt has been used for too long, and the fiber has lost its elasticity, resulting in a decrease in water permeability. The press felt needs to be replaced.