The drying cylinder is usedcast ironThe hollow cylinder with covers at both ends is composed of the cylinder block and the cylinder heads at both ends. The outer diameter is mostly 1000~3000 mm. During the operation, the inner steam will deliverpaperZhang drying and ironing.
Chinese name
Drying cylinder
Foreign name
dryer
Shape
Hollow cylinder made of cast iron with cover at both ends
paper machineCast iron dryers are the key components for paper drying -- Class IPressure vessel。The number of cast iron dryers accounts for about 2/3 of the total number of pressure vessels in the paper industry.The drying cylinder is generally made of HT200 and HT250. In terms of manufacturing quality, it is required that there should be no penetration and excessive sand holes. In order to increase the smoothness of the paper surface, it is required to polish the external surface of the drying cylinder and lath the internal surface, so that the entire drying cylinder wall is consistent in thickness, to ensure the safety, balance and uniform heat transfer of the drying cylinder.The drying cylinder is used to dry the moisture in the paper and decorate the paper surface.
component
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Main components of drying cylinder include: roll shell, spoiler, siphon, end cover, manhole cover, bearing, shaft head, steam joint, etc.
Structure diagram of drying cylinder
Drying principle
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The saturated steam from the steam joint condenses inside the drying cylinder, and the heat released makes the temperature of the drying cylinder rise, thus heating the paper sheets running on the surface of the roll shell.Heat is transferred to the paper in the contact between the paper and the drying cylinder surface.
A large amount of condensed water is generated after the heat released from steam is condensed. Because the rotation of the drying cylinder is attached to the inner surface of the drying cylinder by centrifugal force, the condensed water forms a water ring at a high angular speed, which blocks the transfer of heat to the surface of the drying cylinder. Therefore, a siphon is required to drain the condensed water in time.When the vehicle speed is low, there will be no water ring, but there will also be condensate splashing and accumulating in the dryer.[1]
Main components
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Steam connection
As mentioned earlier, the drying cylinder needs to be filled with steam, and the internal condensed water needs to be discharged.However, the drying cylinder is a rotating cylinder body, so a special joint is required to complete this task, that is, the steam joint.
The steam inlet and condensate outlet are generally composed ofRotary jointIt can be completed at one end of the drying cylinder, or steam can be introduced at one end and condensate can be discharged at the other end.
Schematic diagram of steam joint
The above figure is a typical schematic diagram of the steam joint. Steam and condensate are introduced and discharged at the same end.The journal at this end of the drying cylinder is hollow, so as to provide a channel for steam and condensate.After entering the input end, the steam enters the drying cylinder from the opening of the conveying pipe, and the condensed water is sucked up by the siphon pipe and discharged along the pipeline. This pipeline is inside the conveying pipe.becauseJournalBearing and other components need to be installed on the shaft, so the temperature rise of the shaft journal caused by steam injection will have an adverse effect. Therefore, heat insulation sleeve is used to separate the heat of steam in the transmission pipe from the shaft journal as far as possible.The heat insulation sleeve is fixed on the hollow journal and rotates with the drying cylinder, while the fixed support and delivery pipe are stationary.The end of the insulation sleeve shall be sealed with carbon ring to prevent internal steam leakage.
Perspective view of steam joint
Spoiler bar
The purpose of the spoiler is to destroy the condensate water ring formed in the drying cylinder under high-speed rotation and generate more turbulence.The spoiler bar is installed in the direction of the banner on the inner surface of the drying cylinder. It rotates at the same speed as the drying cylinder, so it will move the water ring to generate turbulence, which is conducive to heat conduction.The position of spoiler bar is drawn in the drying cylinder structure diagram.
common problem
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Wear of drying cylinder shaft head
Because the drying cylinder bears high temperature and pressure during operation, the drying cylinder shaft head is prone to wear, resulting in equipment failure.The traditional repair method is to process non-standard sleeves, and the combination of non-standard sleeves and shaft diameters is prone to problems;Dismantling, machining and repairing have long construction period and high cost.For many years, enterprises have failed to find effective and fast repair methods, and the relatively mature fast repair methods in China are mainly usedPolymer compositesOn site rapid repair, both the repair effect and the repair cost are far better than traditional repair methods such as surfacing, brush plating, etc., with fast repair time, simple process and low cost.The polymer composite material not only ensures 100% contact of its mating surface, but also has its own yielding property, which makes its ability to resist shock and vibration much higher than that of metal materials that cannot yield. At the same time, it expands and contracts with the expansion and contraction of the bearing inner ring, minimizing the possibility of wear, thus ensuring the normal operation of the equipment, reaching or even exceeding the normal service cycle.[2]
Operation method:
1. Mold processing: make standard split mold (bilateral or unilateral positioning);
2. Surface treatment: degreasing, polishing and cleaning to ensure that the surface is clean, dry and solid;
3. Blending materials: accurate proportion and even blending;
4. Coating material: ensure bonding, filling and thickness;
5. Install the mold: apply the release agent, install and fix it to ensure that the excess material is extruded;
6. Demoulding: after curing, remove the mold to clean the excess materials. The materials cannot be knocked, but can be removed by polishing machine, file and other tools to meet the installation requirements.
