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|Stainless Steel And Ceramic
paper cup machine parts,
paper plate making machine parts
The stainless steel body ceramic faceboard foil box used for the dewatering
The foil box consists of face board and frame, and is divided into single-page, double-page and multi-page foil boxes.
1. face board: Long strip board with rake angle, horizontal support surface and backward inclination angle. The bottom is made into various tongue and groove shapes to match the connection bracket.
The face board requires a low coefficient of friction and is wear-resistant. Commonly used materials are high-molecular polyethylene, inlaid ceramic strips, and all-ceramic blades.
High-density polyethylene has a life of about 3 months, low price, can be reground three times, and is only used for low-speed paper machines;
The service life of ceramics can reach several years, and the friction coefficient on the paper making wire is small, and it is easy to keep clean. Although the cost is high and the processing difficulty is large, it is used more and more.
2.Frame: It is a stainless steel box structure, which requires high rigidity and small deformation. The brackets at both ends can be adjusted back and forth and up and down.
3. Dewatering mechanism and characteristics of the foil box:
3.1 Dehydration mechanism: The water attached under the net is first scraped off by the leading edge angle. When the wire slides over the horizontal plane in the front of the chopping board, it forms a wedge-shaped space with the inclined surface at the rear. Due to the relative movement of the two planes gradually separating , And by the adhesion of water, the negative pressure is generated in the wedge-shaped space, thereby accelerating the dehydration process. The released water adhered to the bottom surface of the wire and was pushed to the next chopping board, scraping off the leading edge of the next chopping board.
3.2 Dewatering characteristics: As the dewatering effect of the foil box blade is relatively mild, the wiper blade is often used for dehydration in the high-speed paper machine net to reduce the loss of fiber filler and rubber, and improve the uniformity of the paper sheet.
4. Several problems in the design and use of wiper blades:
The shape and size of the wiper blade have a significant impact on the performance, so there are higher requirements in terms of design and manufacturing.
4.1 Number of blades: single-leaf wipers are convenient and flexible, but the cost is high, and the rigidity of the frame is poor, so they are rarely used; the two-leaf or three-leaf wipers with larger spacing are mostly used at the wettest end. Spacing; 4-6 blade wipers are used in other parts, which has good rigidity and low cost.
4.2 Width of wiper blade: The choice of the width of the wiper blade should mainly be considered from controlling the degree of disturbance of the slurry on the net by the wiper blade. The narrow wiper has great flexibility and has a large disturbance to the pulp. The wide wiper reduces dehydration, which helps to improve the retention of fine substances in the paper web, but the power consumption is large. Generally, a 50 mm wide wiper blade is selected, which can meet the rigidity requirements, but also has sufficient dewatering capacity and slurry disturbance performance, and the power consumption is low.
4.3 The inclination of the wiper blade: Generally speaking, the dehydration of the wiper blade increases to a certain maximum value with the increase of the blade inclination angle. When the inclination angle continues to increase, the dehydration capacity of the chopping blade decreases quickly. As usual, the angle of the inclined surface is between 1-5 °. Select a large value for the maximum inclination angle at high speed (change within 1-5 degrees); select a small value for the maximum inclination angle at low speed (change within 2-3 degrees). When the vehicle speed is low, the angle of dehydration decreases when the angle is too large. Choosing boards with different inclination angles should be used in different parts of the net. Generally speaking, a small-inclined chopping board should be used in the molding area, that is, the wet end of the screen, to control dehydration and reduce disturbance to the slurry. At the dry end of the net case, the inclination of the wiper blade should be increased to enhance dehydration and disturbance.
4.4 The distance between the wiper blades: The distance between the blades directly affects the dehydration efficiency. Generally speaking, at the wet end of the net case, if the spacing between the leaves is appropriately increased, the amount of dehydration of a single sheet will increase, and the phenomenon of pulp skipping will decrease. At the dry end of the mesh case, shortening the pitch of the leaves helps to strengthen dehydration. It can prevent the detached water layer from being sucked back into the paper web again, affecting the dewatering effect of the wiper.
4.5 Front angle of wiper blade: generally between 30-45 °, which is related to vehicle speed. A large front angle can be used at low speed. Generally, a 30 ° angle is used when the speed is higher than 400 m / min. Keep the leading edge of the blades straight, which is prone to defects and build-up. Too much water scraped will cause too little disturbance to the pulp layer, which will be detrimental to the uniformity; too large anterior angle: small amount of water scraped off by the leading edge will cause too much disturbance to the fibers, which is not good for evenness.
4.6 The geometric accuracy of the wiper blade should be high: the most sensitive interval for the change of the dewatering amount of the wiper blade is 15-25 °, which is within the commonly used inclination angle range, which requires that the maintenance and installation of the chopping plate should be relatively high Accuracy
Contact Person: Mr. Mark Zhang