Precautions and maintenance of slewing bearings on the reclaimer.

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The reclaimer is a continuous and efficient bulk loading and unloading machine. It is widely used in raw materials fields of power plants, ports, steel plants, chemical plants, cement plants and other basic industries. It is suitable for strip or circular storage yards. Piles of bulk raw materials such as coal, iron ore, and limestone are taken continuously.

The slewing bearings of the reclaimer are most commonly used in the following three types: tapered roller slewing bearing, trolley type support, and rotary large bearing type support.

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2. Slewing bearing type and structure type

2.1. Trolley type slewing bearing

The trolley type slewing bearing completes the turning motion by rolling the wheel along the circumference.
This type of support requires high assembly and machining accuracy. If it is slightly improper, the wheel rolling circle will not be perpendicular to the radius of gyration, and abnormal noise will occur.

When the slewing device is being repaired, it is necessary to use lifting equipment, large jacks, and necessary fixing and welding. The equipment needs to be disassembled locally, and many safety problems need to be dealt with.

Because of the relatively high height of the trolley itself, this type of support can easily increase the height of the center of gravity of the whole machine, which in turn affects the stability of the whole machine.

2.2. Rotary large bearing slewing bearing

There are many kinds of structural forms in this type of support. Among them, three rows of roller bearings are the most capable ones in various types. They have three races, and the upper and lower and the radial races are separated so that each row The load of the roller can be accurately determined, can withstand large axial forces, tipping moment and large radial force, and is especially suitable for heavy machinery such as reclaimer.
When the slewing device is being repaired, a large amount of work is required to replace the large bearing. It is necessary to use lifting equipment, large jacks, and necessary fixing and welding. The equipment needs to be disassembled locally, and many safety problems need to be dealt with. The maintenance cycle also takes about half a month. In terms of cost, if the large bearing is used as the slewing bearing, if the margin of choice is large, the bearing needs to be replaced in about ten years. The shortest in the country has five or six years to replace the large bearing equipment. The price of large bearings is relatively high, and the price of bearings of about 3 meters is more than 200,000 yuan.
The stacker and reclaimer is a large-scale mechanical equipment for open air operations. When using large rotating bearings, measures must be taken to prevent dust and water. It is very difficult to guarantee the above two. After the dust enters the water, it will increase the wear and corrosion of the bearing and reduce the service life of the bearing. In addition, large bearings should be placed horizontally during transportation and storage, and must be stored in a dry environment. The storage period should exceed a certain period of time, and other storage measures or anti-rust measures should be taken. Although the large bearing is simple to install, small in size and space saving, its cost is still relatively high.

2.3. Conical roller slewing bearing

After the support of the slewing roller, the cost is not much different from other support forms, but it has significant structural features:

2.3.1. No lubrication required: In actual operation, the roller and the bearing are almost unstressed due to the upper and lower pressure of the roller, and the load on the shaft and the bearing is only the additional load when the cage is fixed. Each roller bearing uses oil-impregnated bearings, so no lubrication is required.

2.3.2. Convenient maintenance: When using the conical roller support method, the maintenance is relatively simple and easy. It does not require large lifting equipment and jacks to complete, and the maintenance time is short, the maintenance cost is low, and it can be completed in one day.

2.3.3. The height of the center of gravity of the whole machine is low: because the diameter of the conical roller is relatively small, the overall height of the supporting device will be small, whether under normal working conditions or under high wind conditions, the supporting method is The stability of the machine will be better.

2.3.4. Low cost of spare parts: The conical roller type slewing bearing does not need to be replaced as a whole during maintenance. It only needs to be used with several rollers, and the spare parts cost is low.

2.3.5. Long service life: There are two reasons for the long service life of the tapered roller: First, the shaft and bearing of the tapered roller do not bear the supporting force of the slewing bearing, so that the bearing and the shaft have a long service life; the second is the diameter of the tapered roller. It is much larger than the diameter of the roller in the large bearing of the slewing bearing. Because of the large radius of curvature and the large number of tapered rollers, the contact stress of the tapered roller is small, so the large bearing has a relatively long service life.

2.3.6. Applicable to harsh environments: The stacker and reclaimer are large-scale mechanical equipment for open-air operation. The conical roller does not have to worry about dust and rain in specific use. Dust and rain do not have too much influence on the conical roller. The reason is that the diameter of the conical roller is much larger than the diameter of the roller of the large bearing, and the effect of a small amount of corrosion and dust on the conical roller and raceway is very small. The rollers and raceways should be properly greased during normal operation.

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3. Summary

In the selection of the three slewing modes, in addition to the user’s designation, comprehensive aspects such as maintenance, installation, load capacity, space size, cost, machine stability, etc., the tapered roller slewing is preferred.

Excavator slewing bearing solution for broken teeth

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The problem of slewing bearing breaking teeth mainly occurs in the internal meshing and hard tooth surface (tooth surface hardness ≥HRC50), such as excavators, rotary drills, crawler cranes, etc. The external meshing and soft tooth surface (tooth surface hardness ≤ HRC30), the phenomenon of broken teeth is rarely seen. According to the research and manufacturing experience of domestic slewing slewing bearing and the incomplete statistics of the foreign brand excavator slewing bearing, the probability of broken teeth of different brands of domestic excavators is different at different times, about 1%~2%, and then The rate of broken teeth in the market slewing bearing is as high as 5% to 6%.

Especially on some domestic brands of 5 tons, 7 tons, 8 tons of excavators, even double-digit percentage of large-area broken teeth. The damage of the slewing reducer assembly is always proportional to the slewing bearing broken teeth. The damage of the 20 ton excavator reducer assembly is about twice that of the slewing bearing broken teeth. The slewing bearing modulus of a certain foreign-funded 20-ton excavator is 10, 12, and 14, respectively, but the probability of broken teeth is comparable, or even the opposite.

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The slewing bearing has a clearance at the factory, and the pinion gear is installed on the upper frame. When the main machine is working, the gap of the slewing bearing will cause the pinion gear to have a radial displacement amount La. Under the action of the overturning moment M, the pinion gear An angle of inclination α is generated again. Under normal circumstances, the excavator slewing bearing factory clearance <0.20mm, after a period of use, the slewing bearing clearance <0.30mm in the actual work, the raceway will produce a certain elastic deformation, in the Hitachi excavator A slewing bearing, after the load, the contact area between the raceway and the steel ball is in surface contact (see Figure 2). With such a large contact area, the one-side elastic deformation of the raceway is about 0.20mm, and the bilateral is 0.40. Mm, only the deformation of the raceway is so large, plus the deformation of the mainframe and other factors, the radial offset of the pinion coupled to the frame of the excavator reaches about 1.0mm, corresponding to the size of the gear The amount of extrusion is also about 1.0 mm. Since the pinion gear meshed with the slewing ring is installed in the opposite direction of the boom, when the flank clearance is too small, the displacement is not completed, and the pinion gear is pressed on the large gear. In this case, the slewing bearing raceway should be carried. The load is carried by gears. The repeated extrusion of the large and small gears eventually leads to broken teeth. The conclusion is that the broken teeth of the slewing ring are caused by the meshing of the large and small gears.

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Third, to solve the slewing ring breaking process of excavators

Squeeze and broken teeth of the slewing bearing: the broken teeth usually occur in the upper half of the tooth width direction, and the fracture surface intersects with the upper end surface of the gear teeth and forms an angle of about 45°~60° (see Figure 3 and Figure 4). ), even if the full tooth falls off, the crack is caused by the top-down expansion. The plastic deformation of the gear is also quite obvious, and the upper part is much more serious than the lower part. The width of the entire ring has different degrees of variation. From bottom to top, the width from the root to the top is increasing.

For the problem of broken teeth of slewing bearings for excavators, we have been working hard to find solutions. The specific solutions are divided into the following processes:

1. Ensure that the tooth side clearance of the large and small gear meshing is not less than 0.06X modulus. For a 20-ton excavator, the modulus of the slewing ring is 10 modes, and the flank clearance of the large and small gear meshes is not less than 0.6 mm. In the aftermarket of excavator parts, because the customer pays less attention to the tooth side clearance when the large and small gears mesh, the breaking rate is high, so we will spread the relationship between the broken teeth and the flank clearance, let them understand the flank clearance control. Not good, slewing bearing breaking teeth is inevitable. After several years of publicity, the breaking rate of the slewing bearing of the excavator (accessory market) has dropped from the previous 6% to about 5%.

2. 37° bevel gear slewing bearing. The gear portion on the non-mounting surface of the slewing ring gear is changed from the full tooth width to the chamfering angle of 37°, and the slewing bearing cuts off the frequently broken portion, so that the pressing force cannot be concentrated when the pinion gear is displaced. In the upper part of the tooth width, the gear portion of the slewing bearing does not cause crush cracks in the early stage of use, and can effectively delay the early tooth breaking problem of the slewing ring gear. Through this improvement, after two years of statistics, the slewing bearing’s breaking rate of the excavator aftermarket (accessory market) dropped from the previous 5% to about 4%.

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3. Gradual hardness gear slewing bearing. Since the broken teeth of the slewing ring are caused by the extrusion, how to prevent the large and small gears from being squeezed is the key point. When the gear is induction hardened, the gear heating section is divided into three sections: normal hard zone, transition zone and soft zone. The hardness of the hard zone is HRC50~56, and the hardness of the soft zone is the quenching and hardness of the steel base. Thus, when the large and small gears are meshed and squeezed, the soft region of the upper end surface is deformed by extrusion deformation without being broken. After one year of statistics, the excavator aftermarket (accessory market) used this slewing bearing without broken teeth, which solved the problem of broken teeth.

The method of solving the broken teeth is to increase the flank clearance of the large and small gears, but the increase of the flank clearance will increase the amount of swing of the excavator bucket to the left and right, which is unwilling for any OEM and excavator customers. See the results. The gradual hardness tooth slewing bearing solves this problem very well. It has been introduced above. After the experiment, when the pinion is pressed against the large gear by 2mm, the gradual hardness tooth can work normally, the excavator and the rotary drilling are normal. When working, the crushing amount of the large and small gears does not exceed 2 mm, and the flank clearance when the large and small gears mesh can be appropriately reduced. When the slewing bearing has broken teeth, the slewing speed reduction mechanism also suffers from damage. After the large and small gears mesh without the squeezing, the damage of the slewing speed reduction mechanism is greatly reduced. In this way, the gradual hardness tooth slewing bearing solves the problem of broken teeth, and can control the swing problem of the excavator and the rotary drilling boom, and at the same time reduces the damage of the rotary speed reduction mechanism, and serves the purpose of three arrows.

Fourth, the conclusion

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The gradual hardness tooth slewing bearing has been put on the market for more than a year, and more than 2,000 sets of products have not yet had a set of broken teeth. The gradual hardness tooth slewing bearing has been put on the market for more than one year for the excavator and rotary drilling grading hardness tooth slewing bearing. More than 2,000 sets of products have not yet had a set of broken teeth. Gradual hardness tooth slewing bearing is a revolutionary breakthrough in the problem of engineering machinery broken teeth such as excavators and rotary drilling, which completely solves the problem of broken teeth.

Large slewing bearing processing technology

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Abstract The paper introduces several key processes of large-scale pivoting support and measures taken for the production with the result that the products can meet the requirements marked in the drawings.

Descriptors super huge bearing, processing , quench-hardening, deformation.

Large slewing bearing, also known as slewing bearing or extra large bearing, is a large bearing capable of withstanding comprehensive loads. It can withstand large radial loads, axial loads and tipping moments. Slewing bearings are widely used in hoisting and transporting machinery. , port machinery, ship machinery and other large-scale rotary devices.

Due to the large volume of the large slewing bearing, the small cross-sectional area of the part, the high machining precision, the long process, and the easy deformation, the difficulty of machining increases. We have adopted corresponding technical measures for the support rings and outer rings of the slewing bearings, and according to the design. It is required to be processed, assembled by commissioning and more than one year of use inspection, which fully meets the original design requirements, and some aspects are even higher than the original design requirements.

1. Selection of rough forging

The large-sized workpiece of the slewing bearing has a support ring, an outer ring and a fixing ring. Since the support ring and the fixed ring are thin-walled annular parts, if the blank of one piece needs to be large when forging, and the heat treatment is prevented, the amount of quenching and tempering needs to be increased. Since the dimensions of the inner and outer rings of the retaining ring and the supporting ring are relatively similar, after repeated analysis, it is relatively easy to forge a large forging, and the fixing ring and the supporting ring are forged into one body, so that one set of slewing bearings has two blank forgings, one for outer The ring, the other is a forging of the retaining ring and the support ring.

2. Rough machining

The key to roughing is whether to separate the retaining ring from the support ring. The roughing process is a process before quenching and tempering. If the retaining ring is separated from the support ring, the amount of the retaining ring should be increased, and the deformation during the heat treatment is easy to increase; if it is not separated, during the semi-finishing process, due to the high hardness of the quenching and tempering, the machining and the large ring cut open. It is more difficult. From the perspective of the overall manufacturing process, it is not separated, and then separated after being tempered.

First, the amount of deformation during the quenching and tempering process is reduced.

Second, it is beneficial to better heat treatment, thus ensuring the quality of the heat treatment process. Through this analysis, we decided not to separate the retaining ring from the support ring before heat treatment, thus making the overall The roughing allowance is correspondingly reduced.

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3. Since the fixing ring and the supporting ring require the hardened layer to be 3 to 5 mm, the hardness after surface quenching reaches HRC 55 to 60. The diameter of the part is large, but the cross-sectional area is small. After the car is finished, the surface is quenched. If the deformation is too poor, it can only be scrapped and the loss is too great. If quenching first, the thickness of the hardened layer should be 3~5 mm. If the amount of space is smaller than the shape variable, it will cause waste.

If the amount is larger than the shape variable, it is difficult to process. The amount of deformation is 1. 5 mm, such a 2 mm retention, the amount of the hardened layer is 2 mm, and the thickness of the hardened layer is 5 to 7 mm. Sufficient, after the quenching and tempering process, after the hardness test is passed, we test the support ring and the fixed ring and the outer ring, and find that the deformation amount is up to 1 mm, the minimum is 0.70 mm, and the amount is not exceeded. If it is reworked, it can also be supported by multiple points. The quenching surface can be 1.5 mm. If there are more support points, the retention can be reduced to 1 mm.

4. Finishing

In the turning process, since the hardness is basically HRC 59-60, we use the special alloy tool we developed and use the low-speed small feed for turning. When the amount is 0. 02 mm, it is ground with a bowl-shaped grinding wheel. When required for size, it is ground with a polishing belt to achieve the dimensional and roughness requirements of the drawings, laying the foundation for the manufacture of high quality slewing bearings.

Structure and scope of slewing bearing

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The slewing bearing is also a kind of bearing. The type distribution and structural characteristics of the slewing bearing are also very complicated. There are single row and cross type and roller type slewing bearings. At the same time, to a large extent, The uniform applicability of the slewing ring in various application areas is determined.

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The slewing bearing specifically includes the above seven types of bearings:

  1. Single row four-point contact ball type slewing bearing;
  2. Double row reducer ball type slewing bearing;
  3. Single row cross roller type slewing bearing;
  4. Row roller type slewing bearing;
  5. Light series slewing bearing;
  6. Single row four-point contact ball type slewing bearing;
  7. Single row cross roller type slewing bearing.

Slewing bearings for different types of bearings:

Single row four point contact ball slewing ring
The single-row four-point contact ball slewing ring consists of two races. It is compact and lightweight. The steel ball is in contact with the arc track at four points and can withstand axial force, radial force and tipping moment. Construction machinery such as rotary conveyors, welding operators, small and medium-sized cranes and excavators are available.

Double Row Ball Slewing Bearing
Double row reducer ball slewing bearing

The double volleyball slewing bearing has three races. The steel ball and the spacer block can be directly discharged into the upper and lower raceways. According to the force condition, two rows of steel balls with different diameters are arranged. This open assembly is very convenient, the upper and lower circular races have a bearing angle of 90° and can withstand large axial forces and tipping moments. When the radial force is greater than 0.1 times the axial force, the raceway must be specially designed. The double-row and different-diameter spherical slewing bearings have relatively large axial and radial dimensions and are structurally fastened. It is especially suitable for loading and unloading machines such as tower cranes and truck cranes that require medium and large diameters.

Single row cross roller slewing ring

Single row cross roller type slewing ring consists of two races. It is compact in structure, light in weight, high in manufacturing precision, small in assembly clearance, high in installation accuracy, and 1:1 cross-arrangement of rollers. Force, tipping moment and large radial force are widely used in lifting and transportation, construction machinery and military products.

Three Row Roller Slewing Bearing

Three row roller slewing bearing

The three-row roller type slewing bearing has three races, and the upper and lower and the radial raceways are separated, so that the load of each row of rollers can be accurately determined. It can withstand various loads at the same time. It is the most load-bearing type among the four products. It has large shaft and radial dimensions and is firm in structure. It is especially suitable for heavy machinery requiring large diameter, such as bucket wheel excavator and wheel. Cranes, marine cranes, port cranes, steel run tables and large tonnage truck cranes.

Light series slewing ring

The lightweight slewing bearing has the same structure as the ordinary slewing bearing, and is light in weight and flexible in rotation. Widely used in food machinery, filling machinery, environmental protection machinery and other fields.

Single row four point contact ball slewing ring

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The single-row four-point contact ball slewing ring consists of two races, which is compact and has four points of contact between the steel ball and the circular raceway. It is mainly used in machinery such as truck cranes, tower cranes, excavators, pile drivers, engineering work vehicles, radar scanning equipment, etc., which are subjected to tipping moment, vertical axial force and horizontal tendency force.

Single row cross roller slewing ring

Single row cross roller type slewing ring, consisting of two races, compact structure, high manufacturing precision, small assembly clearance, high requirements for installation accuracy, roller 1:1 cross arrangement, can simultaneously withstand axial force, tilt Rolling torque and large radial forces are widely used in transportation, construction machinery and military products.
There are different types of slewing bearings, and among these types, there are also different structural features. As a result, this also largely determines the importance of slewing bearings in different fields.

Ten of slewing bearing application industry

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1. Solar power generation industry

In the solar power generation system, the solar panel assembly needs to follow the movement of the sun position to rotate up and down, left and right to ensure higher power generation.2. Wind power industry

The wind power generation system is in a harsh environment, with many dusts, strong corrosiveness, large temperature difference, and difficult maintenance. The bearing life is required to be more than 20 years.

Bearing applications: yaw bearing (slewing bearing), pitch bearing (slewing bearing), generator bearing (cylindrical roller bearing, angular contact ball bearing), gearbox bearing (cylindrical roller bearing, deep groove ball bearing), Spindle bearings (centrifugal roller bearings), etc.

3. Mining machinery industry

The working environment of mining machinery is harsh, dust is heavy, load is heavy, impact is large, and bearings are easily damaged. Bearing applications: slewing bearings, double row cylindrical roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings.

4. Construction machinery industry

Construction machinery includes cranes, excavators, bulldozers, road rollers, earth moving machines, etc. The working environment of construction machinery is harsh, dust is heavy, the load is heavy, the mechanical faults are many, and the working time is long.

Bearing applications: slewing bearings, deep groove ball bearings, cylindrical roller bearings, spherical roller bearings, tapered roller bearings.

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5. Metallurgical industry

Metallurgical machinery has rolling mills, continuous casting machines, etc. Its operating conditions are high speed, high load and high temperature, which puts high requirements on the application difficulty of bearings.

Bearing applications: single row, double row, four row tapered roller bearings and cylindrical roller bearings

6. Machine tool industry

Machine tools are moving in the direction of high speed, high precision and high performance.

Bearing applications: full complement cylindrical roller bearings, deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, tapered roller bearings, thrust ball bearings and thrust cylindrical roller bearings

7. Medical industry

With the improvement of quality of life, medical, environmental, rehabilitation and fitness equipment are becoming more widespread. It requires a small noise and smooth operation.
Bearing applications: slewing bearings, deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings and tapered roller bearings

8. Plastic industry

Die casting machines used in the plastics industry to press plastic finished products are extremely load-bearing and require long-lasting continuous operation.
Bearing application: tandem bearing

9. Petroleum industry

Drilling equipment used in the petroleum industry includes mud pumps, winches, top drives, and cranes. Working conditions: heavy load, many sediments, strong corrosiveness and large impact vibration.

Bearing applications: deep groove ball bearings, spherical roller bearings, cylindrical roller bearings, tapered roller bearings, thrust cylindrical roller bearings.

10. Port ship industry

The gantry cranes, vertical cranes and ship cranes used in the port are all working in the open air. The bearing conditions are heavy, corrosive and difficult to lubricate.
Bearing applications: slewing bearings, full complement cylindrical roller bearings, roller bearings.