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Crane is a common engineering machinery equipment. It is mainly used in the construction of bridges, roads, and port projects. Due to the working environment and overloading, there is often no turning action during work, which not only affects the overall performance of the equipment, It also delays work efficiency. Today, we mainly introduce the causes and troubleshooting methods of common crane rotation failures.

The crane does not rotate, mainly dues to the mechanical transmission of the slewing mechanism or its electronic control system fail. Today, we mainly discuss the non-rotational failures of tower cranes (Towers) and gantry cranes, analyze the causes of the failures, and propose ways to eliminate them.

First, mechanical failure

The slewing bearing of the crane acts as a connection between the upper and the chassis in the slewing mechanism while supporting the entire rotating portion of the crane. The main cause of mechanical failure: slewing bearing wear. When the crane works in an environment with strong corrosiveness and dust, or after large rainwater has passed, the steel ball in the slewing bearing is damaged and the raceway is worn. Both will affect the work of the slewing mechanism. In severe cases, the slewing mechanism will experience heavy rotation and noise. Violation of the operation, such as lifting the weight, when using the basic arm of the crane to pull and tilt the heavy objects in the distance to achieve the purpose, often erroneously use the slewing mechanism to diagonally pull, this is a violation of the safe operating procedures. At the same time, the slewing mechanism and the basic arm are also damaged.

Remedy: Repair or replace the slewing ring bearing. Wipe in time, add a proper amount of lubricant to the inside of the slide, and apply some anti-rust oil to the outside. The grease nipple should be unblocked frequently to prevent clogging, and the tightness of the bolts everywhere should be checked frequently to prevent the gap between the upper and lower landslides from being too large due to the looseness of the bolts, resulting in wear of the steel balls and raceways.

Second, the rotary hydraulic system is low

When the pressure of the rotary hydraulic system is low, the sound and speed of the rotary process are normal under the condition of the no-load or light load of the crane; when it is heavy, there will be difficulty in turning or even no turning. The reason for this phenomenon is that the spring of the overload buffer valve of the rotary hydraulic system is softened. The pressure of the rotary hydraulic system is realized by adjusting the screw of the overload buffer valve. This adjustment screw also has the function of sealing the oil passage. In order to ensure the sealing of the oil passage, the screw must be tightened, but the spring cannot be adjusted at will. The pressure is gone. Remedy: When the spring pressure is not enough, only use the spring end to add a washer to solve or replace the new spring.

Third, the rotary electronic control system has failed

First, the rotary motor burns or the carbon brush breaks to produce a short circuit, and the carbon brush wears to cause an open circuit with the slip ring; the second is that the brake electromagnetic coil is burnt, causing the brake friction plate to lock and can not release the brake; the third is the electronic component The damage is broken or the fuse is blown; the fourth is the damage of the contactor that controls the rotation; the fifth is the damage of the relay that controls the rotation; the sixth is the poor contact of the electrical part of the main controller (the main switch).

Remedy: If the rotary motor burns, it is often caused by excessive load, phase loss of the three-phase power line or short circuit. If the slewing load is too large and the three-phase power line of the slewing motor is out of phase, the motor will be burnt. At this time, stop the operation immediately. Carbon brush breaks are prone to short circuits and high-quality carbon brushes should be used. The carbon brush should be maintained in time to replace the carbon brush with excessive wear. If the brake solenoid is burnt, check the solenoid. When checking, turn on the power of the electromagnetic coil to be inspected, and use a screwdriver to check whether the electromagnetic coil generates suction force to the screwdriver. If there is suction, it means that the electromagnetic coil is not broken, otherwise, the electromagnetic coil is broken, and the new electromagnetic coil should be replaced. Also, check the brake lining wear and replace if necessary. If the electronic component is damaged or its fuse is blown, replace the fuse in the electronic component or electronic component. If the contractor and relay that control the rotation are damaged, replace the new one. If the main controller of the swing is in poor contact, adjust or replace the contact or master controller assembly.

If there is a crane rotation failure during work, it should be stopped immediately to prevent the equipment from working, which not only affects the performance of the whole machine but also greatly reduces the life. Luoyang Hengguan Bearing Technology Co., Ltd. is a comprehensive enterprise integrating slewing bearing design, research, and development, production, sales, and service. If you have any other questions, please contact us.

Excavator is an indispensable mechanical device in the construction of today’s engineering equipment. Powerful robotic arms and buckets can excavate the earth and then load it into the transport vehicle. This series of operations are inseparable from the working device of the excavator. The important joint in the working device is the slewing bearing. The quality of the slewing bearing directly affects the normal operation of the excavator. During the daily use of the excavator, sometimes there is a problem that the upper ring and lower ring gaps of the excavator turntable are large, or the bearing is stuck and damaged. How can we use the maintenance to solve these problems?

First, the reason and solution for the large gap between the top ring and bottom ring of the excavator slewing bearing

The reason for the large gap between the upper ring and lower ring sides of the excavator is that the lack of grease lubrication causes the rollers to become smaller when the wear is worn, the butter leaks out, and further causes wear, and then the excavator slewing bearing has a problem of large gap between upper ring and bottom ring. That is, the excavator turntable is disassembled, and then repaired, the roller is replaced and repaired, and the repaired excavator slewing bearing should be replaced in time.

Second, the other problems of the excavator slewing bearing and the maintenance

1. Teeth are broken

Broken tooth is another common problem of excavator slewing bearing. It should be stopped in time after the broken tooth, and repair and replacement should be carried out in time. The broken teeth of the excavator slewing bearing are mostly due to improper adjustment of the side gear of the large and small gears during installation, which does not meet the requirements. Causes the two gears to be misaligned during operation, causing broken teeth; or the meshing gap adjustment between the pinion and the pinion is not required as required, causing the pinion to become stuck when the meshing gear is engaged with the large gear toothing position during operation; The non-parallel axes and the slewing bearing mounting bolts are not tightly fixed, so that the large and small gears are poorly engaged and the teeth are broken.

The excavator slewing bearing should be repaired in time after the broken teeth appear. If it is repaired by the maintenance personnel, it must be replaced in time. In order to avoid the occurrence of broken teeth, maintenance should be carried out when the installation is used. The following points should be made: the backlash should be adjusted strictly according to the requirements; the meshing adjustment should be carried out with the small gear in the position where the green paint is applied, and the test should be carried out according to the requirements. Operation ensures that the two gear axes are parallel; tighten the bolts as required; operate in strict accordance with the operating procedures; ensure that the size gears are clean and check frequently.

2. Abnormal sound

The abnormal sound is also one of the common problems of excavator slewing bearings. Abnormal noise is an abnormal sound. It will have a certain sound when it comes to new products. It is normal, but it should be replaced in time when it lasts for a long time. Sometimes it is installed after installation. There will also be abnormal noise. In this case, it is necessary to check whether the installation is correct. The abnormal noise generated during the use may be the lack of grease in the raceway or the foreign matter mixed in the raceway. When the noise occurs, it is necessary to check the excavation in time. Whether the various structures of the slewing bearing are complete, and the fault is eliminated.

The above is the analysis of how to solve the problem of the upper ring and lower ring clearance of the excavator turntable. For the excavator slewing bearing, there will be many problems in the process of use, such as large gap, broken teeth or abnormal noise. These problems should be repaired or replaced in time. If you can’t solve them yourself, you must contact the manufacturer in time to provide professional guidance to avoid direct damage.

The crane belongs to a large hoisting machine. When the crane rotates the U-turn, the key bearing function is the slewing bearing. When the crane rotates, it bears a large steering force and load, and still can provide stable rotation. However, in daily use, sometimes there is abnormal noise or stuttering. What are the reasons for these phenomena? How can we handle it effectively?

1.The reason of the abnormal sound of the crane slewing bearing.

1. Insufficient lubricating oil
Lubricating oil plays an important role in the rotation of the slewing bearing. Because the steering force is too large when the crane rotates, it is necessary to have lubricating oil for timely lubrication. If the lubricating oil is insufficient, it will cause a stuttering when rotating, and it will also make an abnormal sound.

2.Loose bolts
Loose bolts are also a major reason of the abnormal sound of the crane slewing bearing. Bolts are used to fix the components of the slewing bearing. Loose bolts will naturally cause abnormal sounds in the slewing bearing, and even damage the bearing and the machine. It is not simple problem of abnormal noise.

3. Track wear
The slewing bearing has a matching rotating track, and the track appears worn, which naturally causes abnormal sound of the slewing bearing of the crane.

4.The slewing bearing damage
Damage to the slewing bearing is a serious reason of abnormal noise. If the slewing bearing is damaged, it needs to be replaced or repaired in time, otherwise it will delay the construction progress.

5.Non-standard use
Due to overload or irregular use, the slewing motor is damaged or the rotating gearbox is damaged, resulting in abnormal noise in the slewing bearing.

2. The solution of the abnormal sound of the crane slewing bearing

1. Lubricating oil and non-standard use can be avoided in normal use and maintenance. Therefore, one of the first tasks to solve abnormal noise is to pay attention to the usual maintenance. When the lubricating oil is insufficient, add lubricating oil in time. The machine should be operated in accordance with the process specification to avoid delays due to low-level operation errors.

2. For the problem of loose bolts, it is necessary to strengthen the bolts in time. The problem of loose bolts is a relatively simple problem.

3. It is more troublesome to deal with the problem of track wear and damage of the slewing bearing. The principle of handling is to change a new one and not to use damaged bearings to avoid irreparable damage. For the slewing bearing, the slewing bearing can be repaired, or the new slewing bearing should be replaced in time.

In addition to daily maintenance and replacement of the slewing bearing, choose the appropriate model when selecting the slewing bearing, after all, the crane is not a small machine.

The slewing bearing, also known as the slewing ring bearing, is a very large bearing capable of withstanding the combined load, and can withstand large axial, radial loads and overturning moments at the same time. Mainly used in large-scale mechanical equipment, such as some cranes and excavators and other equipment. The basic structure of the slewing bearing is similar to the common bearing, but in order to adapt to the more complicated environment, the structure of the slewing bearing is mainly composed of the mounting hole, the internal gear or the external gear, the lubricating oil hole and the sealing device. The design is compact, easy to guide and easy to maintain.

1.The working principle of the slewing bearing

The working principle of the slewing bearing is very simple, mainly the way of moving the object to slide and reduce the frictional resistance. Specifically, the slewing bearing mainly relies on lubrication and friction to achieve the purpose of operation. Internally, it relies on the mutual friction between the ball and the steel ring for the purpose of operation. On the outside, it also relies on the frictional force of the slewing bearing and other components to start the operation and rub against each other, thus driving the object to operate. Of course, there is still not enough light to rub. Although it relies on friction to operate, lubrication is also essential. Just like the chain of bicycles, it takes a long time, and the friction is too large, which will affect the use of parts. Therefore, after using this kind of bearing segment time, it is necessary to carry out maintenance in time and brush some lubricating oil to ensure that it can be in a suitable environment.

2.The working mode of the slewing bearing

The slewing bearing has four series of four-point contact ball bearings, double-row angular contact ball bearings, crossed roller bearings, crossed tapered roller bearings and three rows of roller composite bearings. Four point contact ball bearings have high static Load capacity; cross cylindrical roller has high dynamic load capacity; pre-interference of crossed tapered roller bearing can make bearing have greater support rigidity and rotation precision. Three row roller slewing bearing is promoted due to the increase of bearing capacity. To the bearing height, the various forces are respectively subjected to different raceways, so the bearing diameter can be greatly reduced under the same force condition, and thus has a high load carrying capacity.

2.1. Point contact rolling working mode of slewing bearing

The point contact rolling principle of the slewing bearing is mainly used for the four point contact ball slewing bearing and the cross roller slewing bearing. This working principle has a higher requirement on the quality of the steel ball for the combination of the point contact radial axial force, and the track has a uniform angle.

2.2. Surface contact rolling combined working mode of slewing bearing

The surface contact rolling combination working principle of the slewing bearing is mainly used for the three-row roller slewing bearing. Its advantage is that the contact surface is large and the bearing force is evenly rolling and flexible.

2.3. The surface contact of the slewing bearing is combined with the rolling type

The surface contact rolling combined working principle of the slewing bearing is mainly used for the rotary table bearing. Now the new slewing bearing has a compact structure and high precision. Therefore, the surface contact rolling and sliding working mode is suitable.

2.4. The slewing bearing rolling combination scrolling working mode

The rolling combined rolling principle of the slewing bearing is mainly used for the combined ball and column slewing bearing. This principle has the advantages of small eccentricity, long service life and double structure of roller and ball.

The above is the introduction of the working principle and working mode of the slewing bearing. The principle of the slewing bearing is mainly to realize the rotation of the mechanical equipment through the friction. Due to its good performance, slewing bearings are widely used in large-scale rotary devices such as lifting machinery, mining machinery, construction machinery, port machinery, ship machinery and high-precision radar machinery and missile launchers. At the same time, we can design, develop and produce various special structure slewing bearings according to the specific requirements of users.

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.

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.

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%.

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

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.