2022 December the Third Week ITS Technical Knowledge: Discussion on Installation and Maintenance of Reducer

 

Abstract: The reducer is widely used in modern machinery, and its main function is to transfer torque and match speed between each actuator or working machine and the prime mover. Reducers can be divided into two categories according to their different purposes, namely, special reducers and general reducers, which are different in manufacturing, design and use characteristics. The article introduces the installation characteristics of the reducer, takes the reducer installation as an example, analyzes its installation process in depth, and discusses the relevant matters needing attention in the installation and maintenance of the reducer, hoping to provide some theoretical basis and reference value for relevant personnel.

Key words: reducer; Installation; repair

 

1 Installation overview of reducer

1.1 Installation characteristics of reducer

The herringbone gear needs to make the two end faces of the gear perpendicular to the axis, and the plane formed by the center points corresponding to the two helical gears on the left and right sides should also be perpendicular to the axis. In the actual gear assembly and processing process, there will inevitably be some deviation. If it is herringbone gear reducer, when it is engaged correctly, the left and right rotary gears will produce an axial force. Since the axial force generated is in two different directions, it can offset each other. If the herringbone gear reducer does not work properly during the installation of herringbone gear, the reducer will not be able to achieve free alignment in the specific operation process, and one side of the unilateral gear will not be able to engage, and the resulting axial forces will not be able to offset each other. Under the action of heavy load, herringbone gear will produce relatively large axial force, and also produce greater axial force on the bearing. Bearing overheating is largely caused by improper assembly of the reducer.

 

During the specific installation of herringbone gear reducer, the gear shaft shall be reasonably selected and fixed according to the actual needs, and at the same time, another gear shaft matching with this gear shaft shall also have a reasonable free space for movement.

 

If the reducer is not installed properly, it will cause very loud noise and violent vibration, which will cause the support bearing to heat up and be damaged, and ultimately greatly shorten the service life of the bearing. During the installation of large heavy-duty herringbone gear reducer, the fixed stage shall be reasonably determined to ensure that the axial direction of other gear shafts at all levels has a suitable moving space and range.

 

1.2 Installation example of reducer

Φ The main reducer of 90mm pipe pressing machine is a two-stage reducer. The high-speed shaft and low-speed shaft of the reducer are all bearing. During the specific installation, several points need special attention.

 

1) The central symmetrical plane formed by the left and right rotations of the herringbone gear of the reducer is a curved surface. In the specific installation process, consider which shaft should be used as the fixed stage. If the fixed stage is a high-speed shaft, according to the alignment principle of herringbone gear, the power should be transmitted from the high-speed shaft to the intermediate shaft, and then further to the low-speed shaft, which will result in a very large lightning static error, and finally make the axial displacement of the low-speed shaft at the end relatively large. On the contrary, if the low-speed shaft is used as the fixed stage, and it passes through the intermediate shaft and then arrives at the high-speed shaft, the axial displacement of the high-speed shaft will also increase. After comprehensive consideration, it is considered that the power transmission generated by making the intermediate shaft as a fixed stage is better, so that too many errors will not occur and a better configuration quality can be achieved.

 

2) After the fixed stage is determined, in the actual installation process, first of all, it is necessary to determine the positioning and size of the intermediate gear shaft, and install the assembled gear shafts into the gearbox box in order; Next, use the end cap 2 to position the axial direction of the intermediate gear shaft. As shown in Figure 1, there are three precautions during the installation process:

① The low-speed gear shaft needs to be installed in the middle, and 3~4mm clearance needs to be reserved in advance at I, J and K for easy installation.

② A gap of 2-3 mm shall be reserved at E and F in advance for installation.

③ If the high-speed shaft of the reducer adopts double row centripetal spherical bearing, the bearing has a good centripetal property. In the actual operation process, it will have a certain impact on the axial displacement when the high-speed shaft engages. When carrying out reducer box bore and bearing housing, a clearance of 0.02~0.04mm shall be reserved.

 

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Fig. 1 Herringbone gear reducer

 

3) Determining the axial position of the intermediate gear is a very important step. It is necessary to conduct a coloring treatment on the gear surface teeth of the low-speed shaft first, and rotate it for one circle in the direction of operation. The above operations need to be repeated five times, and then the clearances at C, I, J and K are measured and recorded. If the non working surface contacts, it will make it difficult to align the symmetrical surfaces of the two gears naturally. At this time, it is necessary to adjust the axial direction or move the position of the intermediate gear in combination with the measured data. Specific methods:

① If the clearance at position I is too large, move the intermediate gear shaft to the right. In the process of moving, consider turning the thrust surface at the bearing pad end to ensure the clearance at position K.

② If the clearance at K is too small, it will cause the gear shaft of the intermediate stage to move to the left. The clearance at K should be adjusted properly, and the clearances at J and C should also be considered.

 

2 Precautions for installation and maintenance of reducer

2.1 Precautions before installation and maintenance of reducer

1) During the inspection and maintenance of the reducer, the power must be cut off.

2) Before the inspection and maintenance of large reducers, a reasonable and effective? The specific work shall be clearly divided and implemented.

3) Maintenance personnel shall not only have corresponding maintenance qualification, but also have rich and reliable maintenance experience.

4) During the maintenance, it is necessary to confirm the safety and reliability of the guardrail and the bearing in the field work in combination with the actual situation of the site.

5) In case of work at heights, safety areas shall be set up, and some necessary roadblocks shall be set up to ensure the personal safety of workers.

6) In the process of installation or maintenance of mechanical and electrical equipment reducers in public spaces such as some roads, warning signs should be set up in advance, or a person should be specially designated to guide passing vehicles. If necessary, road closure measures can be taken.

 

2.2 Use of lubricating oil

After the reducer is installed and put into normal use, the corresponding model and standard grease shall be selected for lubrication according to the specific characteristics of the reducer. If the reducer is installed vertically, it is difficult to ensure that the bearing at the top plays a lubricating role when lubricating the reducer with lubricating oil. In view of this phenomenon, two lubrication methods or other lubrication methods can be considered for lubrication.

 

2.3 Precautions during installation and maintenance of reducer

Generally speaking, the reducer is equipped with oil drain hole and oil filler hole at a specific location. During the installation and maintenance of the reducer, attention should be paid to these two locations. Here, several matters needing attention during the installation and maintenance of the reducer are analyzed.

 

1) Before installing the reducer, it is necessary to make some necessary inspections on the reducer's appearance to ensure that there is no damage or oil leakage on the reducer's appearance.

 

2) The nameplate of the reducer needs to be checked to determine whether the safe use voltage of the reducer can match the actual power supply voltage. If the actual power supply voltage does not match the safe use voltage of the reducer or the power supply voltage is unstable, consider using a transformer or voltage stabilizer.

 

3) Ensure whether the function and model of the reducer meet the design requirements.

 

4) Further check the fixed base of the reducer, and use the specified installation method to reasonably install it. Try not to loose it in use.

 

5) If a coupling or coupling key is required, it can be installed according to relevant regulations.

 

6) Check whether the reducer is filled with qualified lubricating grease in advance. If yes, it is unnecessary to replace the lubricating oil within 12000 hours.

 

7) During the operation of the reducer, its rated current shall not be greater than the current value marked on its nameplate.

 

8) Before using the reducer, it is necessary to consider whether the surrounding use environment conforms to the use standard of the reducer, such as the temperature, humidity and pH around the reducer. These factors will affect the normal use of the reducer. Generally speaking, the applicable temperature of the reducer is - 10~40 ℃, the applicable humidity is below 90%, and the applicable altitude is below 1000m.

 

9) When the reducer is repaired or removed for installation, make sure that it is completely powered off.

 

10) During the installation and maintenance of the reducer, relevant safety protection facilities must be provided.

 

11) For the motor frequency converter connected to the reducer, it is necessary to provide some supporting power supply lines according to the actual situation.

 

12) If the motor frequency converter connected to the reducer starts at a speed obviously lower than the lowest speed, which does not meet the operation requirements, additional cooling devices need to be installed.

 

13) In case of unidirectional power failure of the reducer, discharge the capacitor before the next operation.

 

14) After ensuring that all the installation parts related to the reducer are installed, start the reducer.

 

3 Conclusion

During the installation and maintenance of herringbone gear reducer, it is necessary to fix the intermediate shaft to ensure that the axial direction and displacement of the gear shaft meet the specification requirements. Although from a theoretical point of view, a good transition fit of the bearing housing can ensure that the displacement will not have too much deviation, in the actual installation and application process, when the gearbox cover is closed, its preload cannot be well guaranteed, which may lead to excessive clearance or interference. Only by correctly understanding the installation and maintenance points of the reducer, correctly installing the reducer at the beginning, and doing a good job in repair, maintenance and other work in the subsequent operation process, can the reducer be operated safely and reliably.

 

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spherical roller bearing is a bearing with drum shaped rollers assembled between the inner ring with two raceways and the outer ring with spherical raceways. spherical roller bearing has two rows of rollers, which mainly bear radial load and axial load in either direction. It has high radial load capacity, especially suitable for working under heavy load or vibration load, but can not bear pure axial load. The outer race of this kind of bearing is spherical, so its centering performance is good and can compensate the coaxiality error.

 

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2022-12-18

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