There are three common ways to transport paper from the couch roll to the press: (1) open, (2) sticky paper feeding, and (3) vacuum paper feeding. Paper and board machines will determine their paper feeding methods based on machine speed and basis weight.
（1）What is open paper feeding?
Transfer from the paper machine wire section to the press section, Medium and low speed fourdrinier paper machines use this method. The method uses the nozzle of the paper machine mesh to cut the wet paper entering the couch roll into 50-100 mm. However, if an ordinary couching roller is used, it is usually manually guided. The process is to glue the narrow paper strip that has passed through the couching roller to a press felt.
(2) What is sticky paper feeding? What are its advantages and what should be paid attention to?
This paper feeding is suitable for medium speed paper machines and low weight paper machines. The wet paper on the couch roll will be stuck under the pick up felt for transportation. It mainly relies on the adhesion of a thin layer of water film on the felt and the slight suction effect of rotation, but it requires the press felt to be strong and surface is flat and has singeing. At present, needle punched press felt is mostly used (The press felt needs to be cleaned when it is running, especially on both sides).
This paper feeding has a simple structure, light paper mesh marks and a long life of the pick up felt. However, this method requires a large content of the pick up felt. In order to avoid embossing, the paper pressure of the pressure roller is low, and the dehydration effect is reduced. It is best not to have too high a weight. It is suitable for paper machines that produce thin sheets of paper.
(3) Vacuum feeding
It is suitable for high speed paper machines, but it is difficult to transfer paper due to high speed. Therefore, most of the transfer from the wire section to the press section uses a vacuum feeding device for closed paper feeding.
After the forming wire passes through the vacuum roller, there is a straight section with an angle of about 45°. In this section, the wet paper is sucked away from the forming fabric by the vacuum feeding roller through the action of vacuum and capillary tubes, and attached to the felt. Then, through the paper feeding press, the wet paper is transferred to the first press felt, and then enters the second press (Note: the paper feeding press and the first press share the same press felt).
For vacuum paper feeding, it is necessary to pay attention to the use of needle punched press felt, good water filtration performance, and no creases during use. The service life is extended from 5-7 days of ordinary felts to 15-17 days, and the forming fabric is prevented from being crushed due to the creases of the
press felt. The BOM press felt produced by Sun Hong can greatly increase the service life of the felt, which can generally reach about 50 days.
In addition, the cleaning of the press felt is also very important: the fibers and fillers adhering to the pick up felt will block the gap holes of the felt, reduce the water filtration effect and openness of the press felt, and seriously affect the performance of the press felt in attracting and transferring paper. Secondly, the smooth surface of the press felt increases the humidity, resulting in poor bonding between wet paper and the felt.
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