It is now widely believed that paper press felts are made to order and that each blanket is designed and manufactured for a certain defined paper machine, part of the technical requirements, according to the speed, production paper type and specifications, etc. Therefore, when designing and selecting press felts, the following factors must be concerned.
The choice of species refers to the choice of blankets suitable for this machine and different parts of the blanket among the many different paper blanket species.
The choice of weight, when the type of blanket chosen is determined, must be based on the many factors of the paper machine reasonable choice of blanket square meters of weight.
The choice of size includes the choice of the length and width of the paper blanket. The actual length and width of the paper blanket in tension on the paper machine to meet normal operation should take into account the changing elongation of the selected blanket.
In actual production, the air permeability of the new blanket, the air permeability when the blanket is in its best condition and the air permeability when the blanket fails under the machine are different, and the air permeability will be worse and worse. If the air permeability is too high. If the air permeability is too large, the water content of the blanket will be too large, the moisture of the paper sheet will not be taken off, the blanket will be permeable to the pulp, etc. If the air permeability is too small, it will lead to the blanket jumping at the vacuum suction box, the wear of the blanket will be aggravated, the paper sheet will be difficult to dehydrate, etc.
For a new paper machine, a simulation test of the press felt is carried out in the same position as a similar paper machine. After the press blanket has been run, it is checked and analysed and, if necessary, the original design is modified.
The choice of press felts depends on the type of paper to be produced, its weight and surface finish requirements, the type of paper machine, the environmental conditions in which the press felts will be used and the available felts cleaning and purification equipment.
When choosing a press felt, we must pay particular attention to the relevant technical parameters of the paper machine.
The line pressure and mechanical load in the press area of the paper machine are directly proportional to the strength requirements of the blanket. The greater the line pressure, the higher the pressure resistance the chosen paper felts can withstand during their life cycle, and the better the elasticity of the paper felts, so that the felts can maintain good water filtration performance and water space for a long time. The greater the mechanical load, the greater the tensile (breaking) strength of the paper felts in transmitting power, and the lower the elongation and shrinkage.
The washing conditions include the configuration of the washing device, the requirements of the washing water quality, the setting of the washing water pressure and vacuum, etc. The washing conditions are directly proportional to the washing effect. When choosing a paper blanket, it is important to pay attention to the washing conditions of the paper machine. Under normal circumstances, we require that every paper machine should have good washing conditions to meet the requirements of the net and blanket, but the reality is that the situation varies from paper machine to paper machine, and from paper machine to paper machine at different times. Therefore, when choosing paper blankets, it is completely necessary to adjust the variety of paper blankets, the quantitative adjustment, the structural ratio and the production process, and the degree of shaping to cater for the needs of the paper machine within a certain range.
The press type of the paper machine determines the dehydration of the wet paper sheet, and the paper felts adapted to different press types are different. It is necessary to select the right paper blanket for the performance according to the press line pressure, the vacuum level, the state of the blanket fit, the state of the vacuum system settings and the washing state. In general, for paper machines with mainly horizontal dewatering, it is advisable to choose blankets with larger compressibility and smaller quantification; for paper machines with vertical dewatering where press dewatering and vacuum suction co-exist, it is generally advisable to choose blankets with smaller compressibility, good elasticity and larger quantification.
With the continuous improvement of papermaking technology and papermaking machinery and equipment level, the requirements for the performance of papermaking blankets are also getting higher and higher, so the performance of papermaking blankets is more refined and more and more varieties. Frequent technical communication with the technical staff of the felt suppliers is a good way to do this. Contact QIANGHUA for more information on press felts.
