How to Remove The Dehydration Marks on The Surface of Press Felt

When the paper passes through the press zone, a large amount of water is squeezed onto the felt, which is then transmitted to the roller or shoe press cover, causing marks. The characteristics of dehydration marks are also fine, straight, and regular marks in the longitudinal direction of the paper, or some regular hole shaped marks. These marks may be imprints on press felt, vacuum rollers, blind hole rollers, grooved rollers, or grooved shoe press covers. When the pressure on the compression line is greater, more water passes through the press felt, making it easier to produce dehydration marks, especially in the later stages of press felt use.

The dehydration marks caused by the base mesh on the paper can easily be confused with the dehydration marks caused by grooves. The method to distinguish between the two: based on the number of imprints per centimeter on the paper, whether it matches the density of the base mesh or the density of the grooves. In general, the line density per centimeter in the base mesh is higher.

The Methods to Solve The Problem of Press Felt Dehydration Marks

(1) If the pressure line in the press zone is relatively high, such as in the shoe press zone, or in positions with high dehydration requirements, such as the first press zone, the weight of the press felt in these positions can be appropriately increased. For press felt manufacturer, it is also necessary to consider the ratio of batt and base fabric, as well as the selection of base fabric. Different layers of base fabric should be selected according to the speed and line pressure of the paper machine.

(2) For the paper machine press section, the material selection of the press roll, groove or blind hole selection are also very important. Suggest reducing the width of grooves or the diameter of blind holes appropriately to reduce the risk of dehydration marks.

(3) If there are dehydration marks during the paper making process, the speed and line pressure can be reduced to alleviate them.

(4) For the high-speed cultural paper machine mentioned above, lightweight non-woven press felt is the best choice. But how to overcome the risk of dehydration marks? Firstly, press felt suppliers can choose a 1+1 base fabric selection, where non-woven base mesh is used for the upper layer and traditional single-layer woven base mesh is used for the lower layer. This can balance the press felt dehydration demand with the actual press felt fluid resistance and reduce dehydration marks. Secondly, the amount of flocking can be appropriately increased to increase the weight of the press felt. Sometimes, due to the low dryness of the paper sheet when out of forming section, the dehydration demand of the press section increases, which can also easily cause dehydration marks on the paper. So, ensuring the forming section dryness of the output paper is also crucial.