Do You Know The Function of Press Felt

The Impact and Classification of Paper Making Felts on Paper Machines.

The press and dryer sections are the main components of paper machine, and their structure and performance are important indicators of the level of paper machine equipment. The design, production, selection, and reasonable configuration of paper making press felts are conducive to fully utilizing the functions and superior performance of the press and dryer sections. They are the prerequisite for the normal operation of paper machines and the guarantee for improving paper output and quality. With the rapid development of papermaking technology, the continuous improvement of papermaking equipment level, and the emergence of some new types of paper with high grade and excellent performance, there are also more and more varieties of paper making felt that match the papermaking machine; The demand for its performance is also increasing. Therefore, in the process of selecting and maintaining the types of paper making felts, it is particularly important to master and understand the types, functions, and properties of paper making felts, as well as their appearance and internal quality, in order to improve the quality of paper and extend the service life of the felts.

In the production process of paper, according to the different parts and functions of the felt used on the paper machine, paper making felt are mainly divided into wet felt and dryer felt. Wet felt are used in the press section of the paper machine, while dryer felt are used in the dryer section.

The Function and Role of Wet Felt on Paper Machines

For the press section of the paper machine, the felt is one of the important factors that affect the speed of dewatering and the improvement of paper performance. It directly affects the dewatering efficiency of the press section, the internal and external quality of the paper, and the production efficiency of the paper machine. This is also the main reason why the press felt is listed as one of the valuable consumables.

With the continuous development of papermaking technology and the continuous improvement of papermaking equipment, the paper making felt that are matched with it have also undergone a long-term process of development and transformation. Nowadays, as the main part of paper making felts, the press felt no longer only has the functions of dewatering, carrying, and conveying, but has also been endowed with more connotations. Overall, it mainly has the following functions.

• Absorb the moisture squeezed out from the wet paper web in the press zone. Press felt has a high porosity and water holding capacity, making it easy to transfer moisture from wet paper sheets to the felt under pressure.
• Support wet paper sheets in the press zone to prevent “embossing”. In the press zone, the press felt is attached to the bottom of the wet paper sheet. The pressure generated by the moisture in the wet paper sheet is dispersed and relieved in different directions through the loose and porous filter area of the felt, so as not to cause the generated pressure head to damage the formed wet paper sheet, resulting in embossing or crushing.
• In the press zone, the stretching performance of the felt evenly distributes pressure on the entire wet paper sheet. Due to the good elasticity recovery and loose porous water filtration area of the felt, when the wet paper and felt enter the press zone at the same time, the pressure they bear gradually increases, and the dehydration pressure energy borne by the wet paper is evenly distributed to the felt, thus achieving uniform and consistent results in the dehydration process of the wet paper in the press zone.
• Give the paper the desired surface properties. In the press section, the wet paper sheet and the felt are tightly adhered under pressure. The surface and internal skeleton state of the press felt will directly affect the surface properties of the paper sheet. The rough surface of the felt and the unreasonable structure of the internal skeleton will inevitably lead to paper defects such as rough paper surface, large difference between two sides, and heavy base cloth marks. In severe cases, it is impossible to alleviate and eliminate them in the subsequent process. So it is very necessary to give the paper the desired surface properties by selecting a reasonable and high-quality press felt.
• In groove press rollers, vacuum press rollers, and blind hole press rollers, there are solid parts and eye holes (or grooves) on the roller surface, and the felt can balance the pressure on the solid part area and the eye hole (or groove) area, thereby eliminating or reducing the hidden marks on the paper. The thick structure, incompressible bottom mesh layer, loose and porous water filtration channels, and good elastic recovery of the press felt are the fundamental factors in reducing and eliminating various printing (hidden) marks.
• Transfer wet paper sheets from the previous press to the next press, playing a role in conveying wet paper sheets.
• The press felt acts as a power conveyor belt, driving all the driven rollers in the press section to rotate.