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Analysis of roll assembly technology and precautions in use management

Description:Roll is the main component of rolling mill, so the assembly technology of roll determines the technical level of rolling mill to a considerable extent and affects the quality of calendering products. Roll is not only an important content of rolling mill design, but also the main management object of organizing production. Therefore, the establishment of reasonable roll use management precautions or system is particularly important to improve the service life and product quality of rolling mill. This paper is applicable to all kinds of rolling mills and rolls in aluminum foil industry, including management precautions of roll use process and roll assembly technology.

Title:Analysis of roll assembly technology and precautions in use management

Keyword:Roll, assembly, use management, circulation card, resume

  • roll assembly technology

2.1 precautions for roll removal

(1) The grinder section needs to receive the roll circulation card before removing the roll. Read the roll circulation card carefully to understand the reasons and status of roll replacement. If any abnormality is found, it shall be reported to the equipment department in time and handled by the equipment department in a unified manner. If it is a shaft

If the bearing end cover, bearing seat, fastening bolt, oil mist or oil-gas lubrication joint is damaged, replacement spare parts shall be prepared at the same time.

(2) After completion, hang it with nylon belt, shake it by hand or knock it symmetrically and properly with copper bar, and then disassemble the bearing seat, bearing and outer ring as a whole.

(3) After roll removal, focus on inspection: whether the bearing, inner and outer rings of the bearing, sealing rings and end cover screws are broken or missing, and check whether the oil mist or oil-gas lubrication channels are blocked. If there are problems, repair or replace them in time, and transfer to the next process only after they are qualified.

① In case of burning of bearing, the number of bearing seat and roll shall be checked in time and recorded. Check whether the lubricating oil is sufficient, whether there is water, aluminum skin and other impurities, whether the seal is damaged and whether the relevant accessories are used correctly – → whether there is obvious friction relative to the rotating parts → external dimension of the bearing seat – → seat hole size, ellipse, taper and deviation from the reference liner surface – → whether the roll neck is burned, roughened Whether the bonding and other phenomena and the runout exceed 0.05 shall be recorded, so as to further analyze the causes and take corresponding measures.

② If it is necessary to disassemble and replace the inner sleeve of four row cylindrical roller bearing, it must be heated by bearing induction heater and shall not exceed 120 C. When it is difficult to disassemble due to burning and sticking, it is strictly prohibited to burn and cut with flame unless it is absolutely necessary. Otherwise, the matching surface between roll neck and bearing will deteriorate and roll deformation will be caused. If it is light, it must be repaired on the grinder, and if it is serious, it must be scrapped. When flame cutting of bearing inner sleeve is necessary under special circumstances, it must be approved by the equipment department, the reason must be clarified and recorded. If it is decided that it can be reused, the roll neck must be polished on the grinder. It is strictly prohibited to put it into use after simple grinding with manual grinding wheel

③ Before the removed work roll is transferred to the grinding roll surface, carefully check the bearing position and sealing position for burning, obvious burr and serious abrasion. If yes, it must be marked, and the bearing position and sealing position shall be repaired in a planned way, and then the working face shall be polished.

④ When grinding the working surface of the roll, carefully check the surface quality of the roll neck or bearing inner sleeve for galling and burns, and measure whether the jump of the roll neck exceeds 0.05mm with a magnetic dial indicator. In case of the above phenomenon, the roll neck of the roll shall be polished.

2.2 precautions for cleaning

(1) dry oil lubricated bearings should check whether the emulsion is lubricated, whether there is wear metal scrap in the oil, whether there is a phenomenon of missing oil content in the exposed ball. If there should be cleaning, clean kerosene should be cleaned, use clean gauze or silk cloth to dip in the kerosene, and then wipe the contaminated oil. The kerosene should be drained or dried with the air pipe after cleaning, then add enough, clean dry oil and assemble back up.

(2) For oil mist or oil-gas lubrication, check whether there are metal chips or oil sludge on the bearing surface and ball spacing joint. If so, clean it. The cleaning method is the same as above.

2.3 assembly precautions

(1) Ensure that the assembly site is clean and prevent foreign matters from entering the bearing housing.

(2) Carefully check whether the roll neck, the end face of the embedded ring shaft end thrust ring at the side of the roll body at the sealing position are scratched, scratched, jammed and other defects. All burrs and sharp corners on the parts matched with the bearing must be removed to avoid falling into the bearing housing during assembly and affecting the assembly quality.

(3) Before assembly, the bearing seat, bearing, sealing ring, screw, oil passage or dry oil quantity shall be checked again to confirm that there is no abnormality. If there is any abnormality, it shall be replaced in time and transferred to the next process after it is qualified.

(4) The load position of the bearing in the bearing seat shall be marked on the equal position of the outer circle (when the outer ring rotates, the load position shall be marked on the inner ring). During the assembly after disassembly and cleaning each time, the load position shall be changed by 90 ° before use, and the bearing area and position shall be recorded, so that the service life of the bearing can be prolonged. Note: the best time to replace the bearing area is during the bearing inspection. At this time, turn the new outer ring bearing area to the designated position of the bearing seat. This activity must be recorded. During each inspection, turn the outer ring to a new bearing area, gradually distribute the load on the whole outer ring and roll it to the surface, which can prolong the service life of the bearing. After the four areas are used in turn — times, it is recommended to turn one side of the bearing part from the lower side to the other side while maintaining the correct sequence of the parts. In this way, the alternating use can make the bearing area evenly distributed on each row of rollers. It is recommended that the disassembly, cleaning and inspection cycle of bearing is 3 to 6 months.

(5) When assembling the roller and bearing box, apply special grease on the roller neck surface. Pay attention to the core alignment and do not damage the bearing or seal of the bearing box. After tightening the adjusting nut, put it back and lock the nut again. The return amount of large bearing is 1 / 8-1 / 6 of the circumference (the thread of nut)

The distance is more than 5 mm), and the small bearing is 1 / 6 ~ 1 / 4.

(6) When installing the bearing baffle, the screws shall be symmetrically and evenly closed to ensure that the baffle presses the bearing evenly. The screws at other parts shall also be pressed symmetrically and evenly.

(7) Special copper bar shall be used when knocking is required for assembly. It is strictly prohibited to strike violently with hammer and steel bar to prevent deformation, bruise and damage. The bearing seat and upper roll are pushed by swing rotation to prevent the seal ring from bumping and deformation.

(8) The end cover bolts shall be free of missing and tightened. If necessary, they can be tightened with a power bar with a length of about 400mm.

(9) Do not change the roll without the permission of the equipment maintenance center; Overall and local structure.

(10) It is strictly prohibited to weld on the roll bearing box at will.

(11) After assembly, the bearing seat shall be manually turned for trial operation to ensure that there are no abnormal phenomena such as jamming and ensure normal use after operation.

(12) after installation, wipe out the extruded grease, dirt on the outer surface of the bearing seat and so on, so as to prevent rolling emulsion from rolling.

(13) After the above processes are completed, the record form of roll assembly resume shall be filled in detail in time.

(14) After the assembly is qualified, it shall be hoisted to the designated place and stored neatly by category.

(15) After all processes are completed, clean the site.

(16) The assembled roll device can be used by the production section after being checked and signed by the team leader or section chief.

2.4 precautions for spot inspection other than bearing

(1) After long-term use, the inner diameter surface of the bearing box will be deformed due to different wall thickness, rolling load and micro vibration wear. Therefore, the inner diameter of the bearing housing shall be measured once every 1 ~ 2 years, and the roundness and wear shall be recorded. The roll diameter is also reduced due to wear, dressing and grinding, and the data are also recorded. The scrapping standard shall be revised according to the actual situation.

(2) The long-term use of the end faces of the insert ring on the roll body side and the thrust collar shoulder on the shaft end side will also produce micro vibration wear and differential wear. In this case, the contact area with the end face of the inner ring is too small, and scratches or thermal cracks will occur on the end face of the inner ring. Therefore, it is necessary to often correct the end face of the retaining shoulder to eliminate the segment difference.

(3) When installing the roll and bearing box, the seal is easy to be damaged. If any damage is found, it shall be replaced.

(4) The monitoring and management of the clearance between the bearing housing and the sliding plate surface of the rolling mill housing is also an important project. If the clearance is too large, the bearing housing will tilt, and torque is easy to be generated on the bearing, resulting in early peeling and burns.

The lubricating grease in the bearing needs to be tested regularly to find out the mechanical and chemical properties of the lubricating grease and the mixing of water and other foreign matters. Especially water, sand and metal dust will shorten the service life of the bearing. Therefore, the spot inspection and maintenance methods such as seal improvement, lubricating oil or grease supply gap, supply method and supply quantity should be corrected according to different degrees.

 

  • Precautions for roll use management

3.1 roll on-line

(1) When taking the roll, the rolling mill operator shall fill in the roll flow card. Before the roll is put on line, the record form of roll assembly resume shall be carefully read. The paired roll placed for more than 8 hours shall be selected. The newly replaced roll shall be preheated to 35 – ~ 50 C and kept warm for more than half an hour Use.

(2) When changing the roll, evenly apply an appropriate amount of grease on the lining plate of the roll bearing box before putting it on the line.

(3) Pay attention to adequate cooling and lubrication of rolls during rolling.

(4) Try to concentrate the materials of the same variety and specification – starting rolling, so as to prolong the service time of a roll profile and reduce the number of roll changes.

(5) After the roll goes online, the roll circulation card shall be filled in in time.

3.2 roll off-line

(1) The mill operator shall submit the roll flow card when delivering the roll. When the roll is normally used to a certain extent, it is necessary to change the roll in a planned way (mainly refers to the change of rolling specification, roll shape, normal production wear or the product throughput reaches the specified quantity, etc.).

3.3 roll change requirements

(1) Backup roll replacement: under normal production conditions, the backup roll device operates continuously for 240 h or half a month, or continuously produces 12 heats, or when the roughness is lower than Ra0.2, check the roll device and replace, grind and maintain it once as appropriate. Precautions: for normal replacement and maintenance, the shift leader shall fill in the backup roll circulation card and go through normal handover procedures with the grinder assembly section. In case of failure, damage or replacement less than the service cycle, the shift leader shall fill in the backup roll circulation card, and handle the normal handover procedures with the grinder assembly section after being signed by the workshop director. After that, the shift leader shall write a written accident report to the production director.

(2) Work roll change: under normal production conditions, 16 coils produced by foil rolling work roll need to be replaced, grinded and maintained once, and 200 coils produced by cold rolling mill work roll need to be replaced, grinded and maintained once.

Precautions: for normal replacement and maintenance, the shift leader shall fill in the work roll flow card and handle the normal handover procedures with the grinder assembly section. In case of failure, damage or replacement within the service cycle, the shift leader shall fill in the work roll flow card and contact the assembly office after being signed by the workshop director Handle normal handover procedures.

In the production process of roll, when there are cracks and peeling caused by factors such as sticking and winding roll, or due to the quality of roll itself and grinding quality, necessary roll replacement shall be carried out.

(4) When the on-line roll needs to be replaced, the removed roll needs to be carefully checked, and the reason for this roll replacement shall be filled in the roll flow card record based on the records of the roll on-line. The position of surface defects shall be marked at the corresponding position with a marking pen, so that the grinder staff can check and reference during grinding.

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