Initial Adaptation Period of Press Felt on Paper Machine

Generally speaking, at the initial stage of a new press felt being installed on the paper machine, its surface flatness, the arrangement direction of surface fibers, moisture content, and air permeability cannot meet the requirements for producing high-quality paper at the required high machine speed of the paper machine. Only after a certain period of idle running under certain pressure and a period of use at low machine speed after being installed on the machine can it reach an ideal state of use. This is the initial adaptation period of the felt. Paper making felts with different structures produced using different processes have different lengths of initial adaptation time. In actual production, we require that the initial adaptation time of the felt be as short as possible.

What are the Content Encompassed By Initial Adaptability of the Press Felt?

• Adaptation time to reach the ideal speed. This is a comprehensive indicator, and only when the status of all parts of the paper machine, including the performance of the paper machine felt, reaches a certain index, can the paper machine achieve the ideal production speed.
• The water-holding capacity of the press felt reaches the ideal state required by the paper machine, the air permeability of the felt is moderate, the pressing pressure of each pass can be increased to normal levels, the pressing and dewatering are smooth, and the vacuum degree of the vacuum box (roller) reaches the desired index.
• The surface of the press felt is smooth and dense, ensuring smooth suction and transfer of wet paper sheets through the felt without sticking to the surface.

Measures to Improve the Initial Adaptability of Press Felt

• Reasonably select the air permeability of press felt, as both too high and too low are not conducive to paper machine production.
• Reasonably develop the production process of press felts, achieving ideal felt performance through the adoption of reasonable needle punching processes, water washing, heat setting processes, structural proportions of the press felt, as well as the fineness and thickness and quantity of the batt fibers layer.
• After the new press felt is installed on the machine, applying appropriate pressure during idle running, moistening it with hot water at around 50℃, softening it with about 5% alkali water, and subjecting it to steam heat pressing at around 0.1MPa in the Yankee dryer cylinder can all shorten the initial adaptation time of the press felt.