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Rolling table failure analysis and its solutions
The conveying roller table is the equipment with a large number of steel rolling production lines, and it is also the equipment with many failures. Due to the continuity of rolling production, any roller table in the rolling production line does not turn, which will cause production interruption. The bevel gear drive roller table supported by the traditional bearing seat is a commonly used structure for medium and larger steel rolling production lines, but the loss of rolling stoppage caused by it is very alarming. For a medium profile production line with an annual output of 300,000 tons of bevel gear drive roller table, the average daily downtime caused by the roller table is more than two hours. For such a production line, one hour of downtime during the production process will cost 5,000 yuan. The above coal consumption and labor cost losses will cause economic losses of more than three million a year. Therefore, reducing the failure rate of the roller table and reducing the time for emergency repair of the roller table failure is one of the main ways to improve the benefits of the steel rolling enterprise.
1. Analysis of the causes of the failure of the rolling table
The working characteristics of the steel rolling table are that the temperature of the conveyed billet is high and the conveying load is relatively large. The roller table supported by the traditional bearing seat has two structures, one is the chain drive structure, and the other is the bevel gear drive structure. for bevel gear drives).
1. Analysis of the causes of roller bearing damage
?、?The bearing seat changes the design oil clearance of the bearing
One of the working characteristics of the steel rolling table is that the temperature of the steel billet being conveyed is high. When the high temperature steel billet is transported by the roller table, the heat will be directly transferred to the bearing ring through the roller table shaft, and the bearing must expand from the ring to the axial and radial directions respectively. .The bearing in the traditional bearing seat is in the axial direction, because the width of the bearing chamber is often more than 10% larger than the width of the bearing, the bearing can expand in the axial direction, and the bearing will not cause "burning damage". However, the bearing is in the radial direction, due to The bearing seat is a structure fixed by upper and lower bolts, and the diameter of the bearing chamber cannot be changed. When the bearing ring continues to expand with the continuous increase of temperature, the outer ring of the bearing is fastened by the bearing seat and cannot expand. Therefore, the original design of the bearing The oil gap between the outer rings will be reduced, and the bearing will generate heat because the oil gap between the outer rings is too small, so that the bearing temperature will rise quickly until it "locks up".
In order to reduce the temperature and improve the bearing life, some companies design the roller bearing seat as a water-penetrating structure. This measure has both advantages and disadvantages for the bearing. The advantage is that the temperature of the outer ring of the bearing is lowered, so that the lubricating oil in the bearing chamber will not be "baked dry", reducing the damage of the bearing due to lack of oil. factor. The downside is that after reducing the temperature of the bearing outer ring (the expansion of the bearing ring still exists), the oil gap between the bearing outer ring will become smaller, which will accelerate the heating and damage of the bearing.
② The bearing seat causes the bearing to run in a non-concentric manner
High temperature, large load and large impact, this is the unchangeable working environment of the rolling table. No matter how flat the roller table is made, it will be deformed during the production process. The two bearing seats fixed on the roller table will be concentric, and the two bearings installed on the same roller table will run under the condition of non-concentricity. The "separation force" caused by this non-concentric operation acts on the bearing, and the service life of the bearing is bound to be greatly reduced.
?、?The bearing seat makes it inconvenient to check and refuel.
The characteristics of steel rolling production require that the roller bearing seat must be checked frequently and refueled frequently, while the upper cover of the traditional bearing seat is fixed with bolts. To check or refuel, the upper cover of the bearing seat must be opened, and the continuity of steel rolling production does not allow frequent Shutdown, so the bearing will often lack oil, which will accelerate the damage of the bearing.
④ The bearing seat is not tightly sealed, water and dust seriously affect the bearing life
The dust generated in the steel rolling production process is not only a lot, but also hard metal compounds. The hard dust entering the bearing will seriously damage the bearing and reduce the bearing life. In addition, due to process or equipment requirements, there are many places where water needs to be sprayed (splashing water) on the roller table. The water enters the bearing chamber with dust, which will damage the bearing more seriously. The upper and lower openings of the traditional bearing seat are all flat contact seals. Most of the input and output shaft holes are not sealed, and a few are just ordinary blanket seals. Under the working environment of high impact, dust and water, large Most of the time, even if there is a seal, it will not work at all. The roller bearing is running in the mixture of oil, water and dust, which seriously affects the bearing life.
2. Failure analysis of bevel gear drive roller table
The bevel gear drive roller table has the advantages of smooth transmission and low noise. However, it has the disadvantages of high failure rate and long replacement time. The failure of the bevel gear drive roller table is mainly due to bearing damage and bevel gear wear. Due to the limited installation space of the roller table driven by the bevel gear, the selected bearings are light and narrow series bearings with low life, plus the axial force caused by the bevel gear, the high failure rate of the bearing is inevitable. In addition to the fast wear and tear of the bevel gear of the drive roller table, the bearing has a slight axial clearance, and the bevel gear will change the meshing state and soon the "bald tip" cannot run. Therefore, the failure of the bevel gear drive roller table is often more than twice that of the other way of driving the roller table.
3. Comparison of emergency repair time for steel rolling table failure
In the steel rolling production process, once the bearing or bevel gear of the roller table fails, it must be repaired to reduce downtime. For the chain drive roller table, in addition to the preparation and hoisting time, the time necessary for emergency repair is mainly used in the disassembly and assembly of the upper cover of the bearing seat, which generally takes about 30 minutes. For the bevel gear drive roller table, in addition to the preparation and hoisting time, the time necessary for emergency repair is mainly used in the disassembly and assembly of the upper cover of the bearing seat, the disassembly and assembly of the bevel gear box, and the disassembly and assembly of the bevel gear and the bearing. . It usually takes more than two hours.
2. The scheme to reduce the failure of the rolling table and the repair time
1. The scheme to reduce the failure of the rolling table and the repair time
From the above analysis, it can be seen that in order to reduce the failure and repair time of the rolling table, it is necessary to change the structure and transmission mode of the roller bearing seat. Over the years, steel rolling workers have done a lot of research and work for this. After years of discussion and use, so far, the bearing seat structure suitable for rolling steel production is a boltless cartridge bearing seat with national patent technology, the patent number is: ZL8.8, and the patentee is Qiping. The transmission mode suitable for the non-frequent forward and reverse starting roller table in steel rolling production is chain drive, and the transmission mode suitable for frequent forward and reverse starting roller table in steel rolling production is the overall cartridge structure of single motor.
Specifically, the structure and transmission scheme of all feeding rollers, billet and finished product conveying rollers are: the combination of the patented boltless cartridge bearing seat and the chain drive; all the front and rear rollers, furnace The structure and transmission scheme of the special roller table such as the front (out of the oven) are: the combination of the patented boltless cartridge bearing seat and the motor single-drag transmission.
2. The effect of reducing the failure of the rolling table and the time for emergency repair
Due to the national patented technology of the boltless cartridge bearing seat, it is specially designed according to the working characteristics of the rolling table. Compared with the bevel gear transmission, the chain drive is not as stable as the bevel gear, and the speed limit is not as high as that of the bevel gear, but it is completely It can meet the needs of steel rolling production. The bevel gear transmission structure is used on the steel rolling production roller table. Not only does it not play its advantages of high speed and stability, but it has more failures, longer repair time and higher maintenance costs than chain transmission. As the saying goes, what is good? Applicability is good.
The above scheme is good because it has the following effects:
?、?It can reduce the investment cost of one-time roller table production by (10-20)%.
?、?The service life of the bearing can be increased by 3 to 5 times, and the failure of the rolling table bearing can be reduced by 80%.
?、?The emergency repair and replacement time can be shortened to less than ten minutes (the bevel gear drive roller table emergency repair and replacement time needs at least two hours), reducing the emergency repair and replacement time by 90%;
④ It can reduce the consumption of spare parts and maintenance costs of the rolling table by 60%.
A medium-profile production line with an annual output of 300,000 tons can reduce the investment in the construction of the roller table by 1-2 million yuan, increase the output by 30,000 to 50,000 tons per year, and reduce the annual loss of 2.5-3.5 million yuan due to roller failures. It can save 1-1.5 million yuan in spare parts and repair costs every year.
3. Analysis of the scheme to reduce the failure of the rolling table and the time for emergency repair
The above solutions have such an effect, let us analyze their structural characteristics at a glance.
1. Structural features and advantages of the patented boltless cartridge bearing seat
The patented bearing seat is composed of a bearing box composed of upper and lower parts and a bearing box positioning frame. The bearing box is inserted in the positioning frame, and the bearing is installed in a bushing clamped between the two bearing boxes. The advantages of the bearing seat are as follows :
?、?The upper and lower insert structure will not reduce the bearing clearance, and the operation will not be "hard"
Since there are no bolts between the upper and lower bearing boxes of the patented technology, when the external temperature rises or the temperature of the bearing itself causes the bearing to expand radially, the distance between the upper and lower bearing boxes increases accordingly, which has the advantage of adjusting the diameter. The function of the outer ring of the bearing allows the outer ring of the bearing to expand, thereby ensuring that the oil gap between the outer rings of the bearing remains unchanged, and the heat does not "lock up" or "burn out". In addition, since the bearing box is inserted into the spacer in two pieces, it is free in the vertical direction. The bearing life will not be shortened due to the misalignment of the bearing seat caused by the deformation of the roller frame
② The upper and lower plug-in structure is used in combination with chain drive, which is easy to disassemble and save time
Because the bearing seat of the patented technology is an up and down insert structure, after it is used in combination with the chain drive, when the roller table fails, just open the drive chain, lift the roller table, and then replace it with a drive chain to run. It is not necessary to disassemble and assemble the bevel gear box, roller bearing and bevel gear like the traditional bearing housing, which can reduce the emergency repair time by 90% and greatly improve the operation rate of the rolling mill.
?、?The upper and lower cartridge structure is used in combination with chain drive, and heavy-duty series bearings can be selected
Using this patented technology, the bearing seat is used in combination with the chain drive. The diameter and thickness of the bearing are not limited by the installation space like the bevel gear. During the design, various heavy-duty series bearings can be selected according to the needs, which can improve the bearing life. 2 ~3 times.
?、?Equipped with protective bushing, the upper cover can be opened during operation, easy to check and refuel
Due to this patented bearing seat, between the upper and lower boxes, there are special-sized bushings with oiling holes, the upper cover can be opened at any time during operation, checked at any time, and refueled at any time, which can ensure that the bearing does not lack oil and has a long life.
?、?Equipped with protective bushing, the sealing structure is reasonable and the sealing effect is good
Due to the patented bearing seat, there are special-sized bushings with oiling holes between the upper and lower boxes, and a sealing gland can be added between the bushing and the end cover as required, which can ensure that even if the bearing seat is installed Running buried in dust, dust will not enter the bearing chamber, thereby improving bearing life.
2. The applicable range of the patented boltless cartridge bearing seat
This patented technology bearing seat is suitable for the following production lines and equipment.
?、?All conveying rollers in the rolling production line from the charging of raw materials to the packaging of finished products.
?、?Various conveying rollers on steel plate flattening production lines and other production lines.
③ Bearing support on the eccentric wheel shaft of rolling steel lifting table and various turning equipment shafts on other metallurgical production lines.
?、?Bearing support for low-speed and large-load transmission shafts in mining, coal, chemical and other industries.
3. Analysis of structural characteristics and advantages of chain drive
Compared with the bevel gear drive, the chain drive is used in the steel rolling table drive and has the following advantages:
① There are few failures. The first reason is that the chain driven by the chain is a roller chain. During operation, the roller of the chain itself and between the roller and the sprocket are rolling friction, while the bevel gear and the bevel gear are sliding friction, and the friction coefficient is different by two. order of magnitude. Second, the roller table bearing of the chain drive can be selected from the heavy-duty series according to the needs. The design life of the bearing itself is three times that of the bevel gear drive roller table. The third is that the chain drive does not have the axial force generated by the bevel gear drive on the bearing.
?、?Low cost. The first reason is that the roller chain used in the chain drive is a standard part, and all we need to process is a sprocket, and the processing difficulty and processing volume are much smaller than bevel gears, bevel gear boxes and connecting shafts. Second, the weight of the sprocket and chain is only one-third to one-fifth of the weight of the bevel gear, the bevel gear box and the connecting shaft. The third is that the width of the roller rack at the chain drive end is only one third of the width of the roller rack at the bevel gear box.
?、?Fast replacement. When replacing the chain drive roller table, it is only necessary to disassemble and assemble the head (using the patented insert bearing seat), and when replacing the bevel gear drive roller table, not only the bevel gear box should be disassembled, but also the bevel gear connecting the shaft should be replaced. , but also disassemble the bevel gear and bearing. Therefore, the time to replace the chain drive roller table is only one tenth of the time to replace the bevel gear roller table.
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15358968703
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15358968703