How Are The Base Fabric Marks of The Press Felt Produced? How To Deal with It?

The press section of the paper machine is the part most likely to have marks in the paper making process. The dryness of the paper when it leaves the net is about 20%. The wetter the paper is when it enters the press section, the easier it is to change the arrangement of the fibers, causing the fibers to shift, thus causing marks.

During the use of the press felt, the base fabric may be exposed due to the wear of the surface fluff, and then printed on the paper. Obvious and dense thin strips can be observed in the longitudinal direction of the paper. Generally speaking, base fabric marks often appear in the middle and late stages of the use of the press felt. During the papermaking process, it is necessary to pay attention to the degree of use of the press felt. Within an acceptable range, the line pressure of the press section should be appropriately reduced to reduce the base fabric marks. However, if the reduction of the line pressure still does not improve, the press felt needs to be replaced.

In other cases, the press felt may be damaged too much during use due to excessive spray water pressure, nozzle wear causing water flow dispersion, or the vacuum box vacuum is too high, and the vacuum box panel is too rough, which may cause the press felt to be damaged too much during use, resulting in base fabric marks. It is necessary to check the high-pressure water spray pressure, nozzle status and vacuum box configuration of the paper machine. In addition, it is also necessary to observe the conditions of the pressing rollers and felt rollers in contact with the felt.

If regular fine lines appear on the paper within a short period of time after the press felt is put on the machine, it may be caused by unreasonable design of the felt. If the press felt is too light, it will have excessive water passing through the pressure zone, resulting in dehydration marks on the paper.

If the felt initially has base fabric marks, the following methods can be tried:

(1) Increase the weight of the fluff in the press felt to increase its wear resistance and reduce base fabric marks. Increasing the weight of the fluff can increase the moisture content of the press felt and appropriately increase the water flow resistance when it passes through the pressure zone, thereby reducing the dehydration speed and reducing the base fabric marks printed on the paper due to excessive dehydration.

(2) Increase the weight of the base fabric of the press felt to facilitate fiber elasticity and reduce the pressure on the base fabric. This can be achieved by increasing the number of layers and the density of the warp and weft lines of the base fabric.

(3) Choose base fabrics with different weaving methods according to the different positions on the paper machine and the requirements of the paper. Usually, the base fabric marks of plain Press felt are more serious, but the broken twill can alleviate them.