Sep. 26, 2019
Find here details of Carpet Base Cloth Wide Rapier Loom on our website. Today we would like to talk about the characteristics of papermaking blankets.
The papermaking process is inseparable from the papermaking felt. It can be said that the papermaking process cannot be realized without a papermaking felt on a modern paper machine. Although papermaking blankets account for only a small percentage of the total cost of papermaking, their quality has a significant impact on the papermaking process. The blanket manufacturer is also striving to improve the new requirements for the development of papermaking technology from the aspects of fiber raw material selection, weaving methods, needle punching technology and post-treatment technology.
Carpet Base Cloth Wide Rapier Loom
So what are the quality parameters of papermaking blankets? Wide Rapier Loom Manufacturer would like to tell you.
1. Length and width of the blanket
The width of the blanket should be sufficient to support the full width of the paper. The wide width of the blanket not only increases the unit consumption of the blanket, but even tears the blanket; if the width of the blanket is narrow, the blanket may not effectively cover the suction box panel of the paper machine, and cannot support Full-width paper.
The length of the felt must match the operating structure of the paper machine and be able to withstand the required tension during operation of the machine. If the length of the felt is too long, the running tension required by the paper machine will not be reached, and if the length of the felt is too short, it will not be installed properly.
2. The weight of the blanket
During the papermaking operation, the felt and the wet paper sheet are subjected to a pressing force in the thickness direction between a pair of press rolls in the press section of the paper machine, which requires a moderate weight of the felt square, a reasonable carpet structure, and a certain amount of acceptance. The ability to squeeze out moisture from wet sheets. The square meter weight deviation of the blanket is too large, so that the dewatering rate of the wet paper sheet is lowered, the paper sheet is easy to produce a blanket print, and the like, and more paper diseases such as wet paper embossing and local dehydration are also caused.
3. Compressibility of the blanket
The blanket must maintain a certain degree of compressibility. After the blanket is used, the pore volume is gradually reduced, and the diameter of the capillary tube in the felt is gradually reduced. As a result, the passage of the fluid flow and the permeability of the felt are reduced, and the liquid resistance of the nip is increased. When the thickness of the felt is reduced to a certain extent, the water filtration of the felt cannot meet the requirements of use, indicating the end of the life of the felt. The anti-compression ability of the felt is directly related to whether the performance of the felt remains stable, and whether the paper machine reaches the steady state press.
4. Abrasion resistance
The abrasion resistance of the felt is the extent to which the felt is damaged by the friction between the rollers and the vacuum components during the operation of the press section of the simulated paper machine under certain pressure conditions. The felt acts to transmit power and drive the driven roller of the press section to generate friction with the surface of a part of the fixing member of the press section. However, in terms of the service life and performance of the felt, the higher the warp breaking strength of the paper felt and the abrasion resistance index of the surface fiber layer, the more advantageous.
5. Saturated water
The saturated moisture of the felt refers to the amount of water that can be absorbed by the static underlying blanket and is used to characterize the ability of the felt to absorb moisture from the wet paper in the nip. The felt should have a volume of void to absorb the water squeezed from the wet paper. At the same time, the felt can reach the vacuum dehydration capacity of the vacuum dewatering box design under a certain pressure. The new felt not only absorbs more water than the old felt, but also the water in the blanket is more easily absorbed by the vacuum suction box and is more easily dewatered.
6. Air permeability
The dry blanket's air permeability refers to the amount of air per square meter per minute that can be transmitted at a pressure of 127 Pa.
The smoothness of the felt directly affects the surface properties and print quality of the paper. The smoothness of the felt is mainly determined by the base fabric and the surface fibers. The smoothness of the felt base fabric can be measured by its roughness, but the smoothness of the felt is determined by the combination of fiber fineness, fiber uniformity, needle type, and finishing process.
The main reason for the generation of the felt base fabric marks on the paper sheet may be that the base fabric of the felt base fabric is too thick, the amount of short fibers on the surface of the felt is too small or falls off, so that the wet paper is subjected to uneven pressure in the nip. The fiber print on the surface of the felt sheet is mostly caused by excessive fiber fibrillation and fluffing on the surface of the felt.
The warp breaking strength of a felt refers to the maximum tensile strength (N) produced by cutting a fabric sample of a certain width (50 mm) on a tensile tester and measuring the tensile strength of the warp until the sample breaks. Periodic stress and fatigue during the pressing process can cause elongation, compression and horizontal strain of the felt. In terms of the service life and performance of the felt, the higher the warp breaking strength and wear resistance index of the paper felt is, the more advantageous.
9. Flow resistance of the blanket
The permeable tester measures the longitudinal, lateral and vertical flow resistance of the felt and reduces the fluid pressure in the nip. The press dewatering efficiency can be improved, and the flow resistance of the bottom net base cloth felt and the pressure of the nip pressure fluid are both small, so the press dewatering efficiency is high.
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