The Impact of Press Felt Size Stability on Papermaking

The stability of press felt size is directly related to the performance of many uses.

Elongation Rate of Press Felt

Excessive elongation of press felt length can lead to a decrease in the felt’s fracture strength, smaller water filtration pores, reduced water filtration efficiency, width shrinkage, and other damage. At the same time, it can also cause the felt length to exceed the adjustment range of the tensioner, resulting in the felt not being tensioned and causing a lot of inconvenience in actual operation.

Shrinkage Rate of Press Felt

Excessive shrinkage of press felt width can lead to insufficient effective width, air leakage in the vacuum box (roller), reduced water filtration pores in the felt, decreased water filtration efficiency, unstable operation of the felt, difficulty in paper feeding, fluctuation of moisture content in wet paper sheets, frequent breakage of wet paper sheets, and other problems. Excessive local shrinkage of the press felt can also cause the polarizer to work frequently on a large scale, leading to phenomena such as deviation and breakage.

Press Felt Compression Ratio of Thickness

Excessive compression ratio of felt thickness can lead to loss of elasticity,  press felt compaction, decreased air permeability, decreased water holding porosity, decreased water filtration performance, difficulty in dewatering paper sheets, and uneven dewatering of paper sheets.

As shown in Figures 1 and 2, the changes in air permeability and corresponding thickness when using a 1200g/m2 double layer press felt on paper machine with speed of 400m/min are illustrated as an example to demonstrate the relationship between the changes in felt thickness and air permeability.

In daily work, we must maintain the stability of felt size to reduce the occurrence of damages. Maintaining the stability of  pres felt size is a necessary condition for ensuring stable production, improving efficiency, and producing high-quality paper in paper machines; Maintaining the stability of the size of press felt not only requires strict control during the production process, but also proper operation and maintenance during use.