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First, the reason for the track chain derailment 1, the excavator itself parts processing and assembly problems; The main components bear a large load when working, and it is easy to wear after using for a long time; 2, the expansion cylinder failure, track too loose; 3, improper adjustment of the gap between the guide wheel, bracket and the wear reducer plate; 4, a long time to walk on the stone, resulting in uneven force, track pin fracture, chain wear, broken; 5, there are foreign bodies between the guide wheel and the track frame, improper walking operation, uneven stress on the track, resulting in the track being pulled or broken.   Second, excavator track chain assembly skills Excavator in the work often appear the phenomenon of track chain plate fall off, especially driving a long time to use the machine, the operator is not experienced enough often have no countermeasures, so how to assemble the chain after falling off? How to reduce or avoid this phenomenon to a certain extent? Work before assembly 1. Inform the construction party that there is a problem with walking and the work needs to be stopped for processing. 2, judge the surrounding environment of the machine, after the track falls off, try to choose a spacious, flat and hard site, there are obstacles around the track, such as mounds or stones, branches, you can use the excavator bucket to sweep, maintain a certain rotation and walking range. 3, determine the degree of excavator falling off, if the object is broken caused by falling off or other faults should be notified in time to repair personnel. Check whether there is dirt, sand and stone in the excavator track, if there is a large number of objects, it is necessary to clean up in time. It is understood that the reason for most of the tracks falling off is that the track device is too much debris, and it falls off during the steering operation, especially when the machine track link is in poor condition, the gap is large after wear, and it is easier to fall off. 4. Use a wrench or a sleeve to remove the track filling butter nozzle, and use the excavator bucket to prop up the falling side of the track and turn the track, the butter will be squeezed out and the driving wheel will shrink back.Method of assembling track Method 1: Turn the chain movable pin joint to the middle height of the two ends, knock it out, then the track plate can be placed flat, in a shape, and the excavator walks unilaterally to the top of the track. At this point we need an iron bar to "guide" the track plate to the "right track". Assemble from the driving wheel, put the iron rod under the track plate, prop up the machine to rotate the track, then also need a person in the cab operation and walk, while lifting the track at the same time turn the track forward, through the upper bracket wheel, walk to the position of the guide wheel, then an object can be placed at the guide wheel, then the two sides of the track butt, assembly on the live pin shaft. This method is also suitable for rubber track assembly, due to the aging of the live pin, it is difficult to knock, and even requires welding and cutting equipment to assemble, so this method is not recommended under normal circumstances. Method 2: When one side of the track falls off, clean up the debris around the track, you must first butt the drive wheel, hook the upper track with a bucket, align the drive wheel and enter the track, get off the car with an iron rod to adjust the alignment of the drive teeth, and align the upper tug, this step has been completed one-third. Prop up the machine to walk unilaterally to make the track straight, prop up the machine again and get off the car to adjust the lower track, and try to make the heavy wheel align the track after the track falls. By this step, two thirds have been completed. It is only necessary to gently lift the excavator with the bucket teeth to hook the track, so that the guide wheel enters the track, and then adjust the track to align the guide wheel, and then turn the track to add butter, and the track has been assembled. 4 Precautions for excavator track adjustment In the process of using the excavator, it is necessary to pay attention to the adjustment of the track tension according to the difference in soil quality of different construction sites, so as to extend the service life of the excavator track. Situation 1: When the construction site is full of pebbles, it is best to adjust the track slightly loose; Benefits: When walking on the pebble, it can avoid the bending of the track plate. Situation 2: When the soil is soft, the track should be adjusted slightly loosely; Benefits: It is easy to attach soil to the track and rail link to prevent the abnormal pressure exerted on the rail link due to the attachment of soil. Situation 3: In the solid and flat ground construction practice: it is best to adjust the track slightly tighter; Benefits: When the loose track droops too much, there may be contact with the frame and damage the frame. Track adjustment too tight: If the track is too tight, there will be a decrease in walking speed and walking power. This will not only lead to a decrease in working efficiency, but also cause abnormal wear due to excessive friction applied to the pins and bushings. Track is too loose: The track loosely rests on the drive wheel and sprocket, causing more wear or damage. Moreover, when the loose track droops too much, it may contact the frame and damage the frame. In this way, even if the lower walking body is strengthened, if the correct adjustment is not made, it will lead to unexpected failure.

The support wheel is fixed under the wheel frame with screws to support the mass of the machine and spread the mass across the track plate. At the same time, it also relies on its roller flange to clamp the chain rail without lateral slippage (derailment) of the track, ensuring that the mechanical movement along the track direction has small rolling resistance and the life of mud and water operation. The support wheel and the guide wheel, driving teeth, tug and track together constitute the four wheels of the rotary excavator walking system, in which the support wheel plays a role in bearing the weight of the rotary excavator walking system lubrication is very important, many heavy wheel bearing problems and lead to the failure of parts is because there is no lubrication maintenance and did not find the oil leakage situation in time. While doing a good job of lubrication, we must pay attention to whether the heavy wheel of the rotary excavator has oil leakage. Of course, everything should be appropriate, and the lubrication of the heavy wheel of the rotary excavator can not be excessive.

For the rotary motor reducer, there is generally an oil scale above the rotary motor, and the oil scale can be pulled out during daily inspection to observe whether the gear oil level is between the two observation holes at the bottom of the scale, the small hole at the bottom of the scale represents the lowest liquid level, the small hole above represents the highest liquid level, and the gear oil level is normal between the two observation holes. When the liquid level is lower than the bottom hole, the gear oil should be added in time. Generally, the excavator gear oil is best replaced once in 1000 hours, and the brand or use situation is slightly different.   Rotary motor reducer:   1, need to open the oil outlet under the rotary gear box, the following container to undertake, and then release the waste oil.   2, clean the drain port bolt with diesel oil, and tighten the drain port bolt after draining.   3, add the new gear oil from the fuel port, add the oil to the scale between the upper and lower scales.   4. Tighten and tighten the refueling bolt.       Travelling motor reducer:   1, after the equipment is stopped, open the oil discharge port under the walking reducer, and use the container to accept the clean oil.   2. Clean the oil drain bolt and tighten the oil drain bolt after draining.   3. Add the new gear oil from the refueling port, observe from the middle observation window of the reducer, and stop refueling when the oil overflows from the observation port.   4. Tighten and tighten the refueling bolt.       Note: The above operation of the excavator must turn off the engine, and check the oil level and replace it in the cold state after the excavator is stopped.  

The supporting wheel of excavator carries its own mass and operation load, and the property of the supporting wheel is an important standard to measure its quality. This paper analyzes the property of the supporting wheel, damage and causes. The main shaft is made of 50Mn high-quality carbon structural steel with C content of 0.48%~0.56%, Si content of 0.17%~0.37%, Mn content of 0.7%~1.0%, S content of less than 0.035%, P content of less than 0.035%, Cr content of less than 0.25%, Ni content of less than 0.30%. The Cu content is less than 0.25%.   Among them, Mn is an important element in alloy steel, which can improve the forging and plasticity of steel, and ensure that the material has enough toughness and wear resistance. After heat treatment, 50Mn steel has higher strength and hardness, excellent hardenability, deeper hardening layer, finer pearlite structure, and better mechanical properties.   The main shaft design standard requires that the depth of the hardened layer T is 2~7mm, and the quenching hardness is 50~62HRC. In order to improve the wear resistance of the support wheel body, the wheel body material is 40Mn2 alloy structural steel. The content of C is 0.37% to 0.44%, Si is 0.17% to 0.37%, Mn is 1.4% to 1.8%, P is less than 0.030%, and S is less than 0.030%.   The wheel body is formed by forging. After forming, the blank of the wheel body is tempered and the hardness reaches 26~32HRC to keep the inside of the wheel body with high strength, plasticity, toughness and comprehensive mechanical properties.   The surface of the wheel body is quenched to improve the hardness and wear resistance of the track surface of the support wheel. The hardening hardness is 50~58HRC, and the depth of the hardening layer is 6~12mm, so that the hardness of the track surface is basically close to the hardness of the chain rail section (48~58HRC).   Seal O-ring groove size and surface roughness should meet the design requirements, the matching surface should be chamfered, and clean burrs and sharp edges.

The guide wheel is mainly used to guide the track to wind correctly, and to prevent its deviation and deviation.   At the same time, the guide wheel and the tension device work together to adjust the tension of the track, mitigate the impact force from the road when moving forward, and reduce the vibration of the fuselage.   Therefore, the guide wheel is essential in the chassis movement. Operational hour   When working, the guide wheel is easily covered with mud, stones and other debris. If not cleaned up in time, these debris will affect the normal work of the guide wheel, and even damage the wheel body. The operating habits of daily work will also have a greater impact on the wear of the guide wheel. In short, the maintenance of the guide wheel is of great significance to ensure the normal work and extend the service life of the tracked construction machinery.   It should be cleaned regularly, checked for wear and seal status, and pay attention to operating habits to ensure that the guide wheel is in good working condition.   Bear in mind   Keep good habits   For example, walking on inclined ground for a long time and turning suddenly will make the side of the rail link contact with the side of the drive wheel, the guide wheel and the support wheel, which will aggravate the side wear of the wheel edge.   Therefore, long-term slope operation and sudden turning should be avoided as far as possible, and the use of straight line travel and large turns can effectively reduce wear.   After job   After each work, it is recommended to clean the guide wheel with clean water to remove debris and dirt on the surface. The normal operation of the guide wheel is required to have a good seal and internal lubrication.   Bear in mind   Periodic lubrication maintenance   Check the guide wheel float seal and shaft head seal regularly to ensure the seal status inside the guide wheel and ensure good lubrication between the guide wheel shaft and the plain bearing sleeve.   Once the guide wheel seal failure is found, the seal should be replaced or repaired in time to avoid abnormal wear between the wheel shaft and the sleeve due to leakage, and then lead to damage to the guide wheel. When the guide wheel is working for a long time, the tread of the wheel body and the part of the wheel rim will have different degrees of wear.   Bear in mind   Timely replacement   If the guide wheel with serious wear is not replaced in time, it will lose its original effect and even affect the normal operation of the equipment.   Therefore, in each maintenance, it is recommended to check the wear of the guide wheel, and once the guide wheel is found to exceed the wear limit standard, it should be replaced in time.

1) According to the damage of the gear ring, determine the position of the fixed hole and the damaged section that needs to be replaced, and then cut the section of teeth to be replaced with gas cutting.   (2) According to the parts of the gear ring that need to be repaired, the insert is processed, or the corresponding part of the other old gear ring is cut out a relatively intact gear tooth under the condition of ensuring the pitch, and the groove shape is cut out at the joint.   (3) Determine the position of the insert fixing hole, punch the hole to fix it in the corresponding part of the gear ring, pay attention to ensure the accuracy of the fixed hole position.   (4) In order to ensure that the weld has higher strength and can withstand greater impact and vibration, the junction 507 electrode with a diameter of Φ4mm is selected, and the electrode should be baked at 250 ~ 350℃ for 1h before use.   (5) Using AX3500 DC arc welding machine DC reverse welding, the current is 130 ~ 140A. (1) Preheat before welding, use 2 large gas welding guns to heat the welding surface to about 200℃.   (2) Using the temper weld method, the latter weld plays a tempering role on the previous weld, which is conducive to eliminating the hardened structure generated by the previous weld.   (3) Because of the large groove, when welding the first weld, it should be welded slightly thinner to reduce the melting width and reduce the carbon content of the steel. When welding, the electrode tilts forward about 15°, straight forward, and pay attention to filling the arc pit when the arc is closed to avoid arc pit cracks. After welding, use a small pointed hammer to quickly hammer the weld and both sides to relax the stress until the weld appears dense pitting. Continue welding when the weld cools down to about 200℃.   (4) The welding method of each weld after the first weld is the same as that of the first weld, the electrode can be slightly pendulum, in order to avoid porosity, do not pendulum too large.   (5) In order to eliminate the hardened structure and stress after welding, the weld and both sides are heated to about 600 ~ 650℃ with oxygen acetylene flame, and the heat is kept for 20min, and then the weld is covered with asbestos, hydrated lime powder or dry sand, and the weld is slowly cooled to room temperature.   (6) Polish the weld with the polishing wheel, so that the tooth ring repair is completed. The process of repairing tooth ring with segment insert is simple, the technical requirement is low, the repair time is short and the repair quality is high. The service life of the tooth ring repaired with the old insert is about 1/3 of the life of the new tooth ring, and the service life of the tooth ring repaired with the new insert is equivalent to the life of the new tooth ring. The method can be used to insert the tooth ring repeatedly, and the economic benefit is remarkable.