Locomotive rolling bearing fault generation and diagnosis method

 Locomotive rolling bearing fault generation and diagnosis method

    Abstract: This paper introduces the simple diagnosis and precision diagnosis of locomotive rolling imported bearings, and enumerates the detection cases.

    Key words: locomotive rolling imported bearing fault detection
   
    1 Introduction

    As the main components of the locomotive, especially the traction motor and axle box bearing, the imported function plays a decisive role in the safe transportation. When the locomotive runs on the line, once the bearing fails, the whole train will not run, and the transportation line will be blocked. In particular, the passenger trains fail, and the negative impact is even greater. At the same time, once the locomotive bearings fail, it is very difficult to repair the locomotives. Therefore, preventing and reducing the occurrence of locomotive bearing faults is very dangerous for the safe transportation of locomotives. It is important to be able to detect the bearing with hidden troubles before the bearing is loaded, and to ensure that the qualified bearing accessories are on the car is the focus of this paper.

    2 bearing failure

    Severe damage of the bearing is often not caused by a single cause. However, under a combination of several aspects, a vicious cycle occurs under severe operating conditions, resulting in serious burning of the bearing. Therefore, after an accident, it is often difficult to judge What causes it, it also gives us some difficulties in formulating relevant measures. For the convenience of discussion, we first analyze the causes of bearing failures from several aspects.

    2.1 Abnormal wear of the bearing

    2.1.1 When the bearing is used for a period of time, the bearing inner ring, rolling element, cage, outer ring, raceway, etc. will produce certain defects and scars, resulting in poor lubrication of the bearing, causing heat generation of the bearing, long-term heating, resulting in:

    (1) Dilution of bearing lubricants.

    (2) Accelerate the fatigue of the material and reduce the hardness. Due to the above reasons, a vicious cycle is further formed, and the overheating is accelerated to burn the bearing. Severe bearing inner ring displacement, rolling element out of round, collision heat, and finally welded together. Therefore, when running on the line, if the bearing is found to be severely heated and smokes, do not stop, but keep running to the front station, because the overheated bearing is in a molten state at this moment, once it stops cooling, it can no longer walk and block the positive line.
 
    2.1.2 It is very important for the oil supply maintenance of locomotive bearings, especially for the proper amount of oil to ensure that the bearing has good lubrication. It is easy to cause bearing failure due to lack of oil and excessive oiling. Poor lubrication and heat, more often it is easy to cause stirring and overheating, so it is necessary to properly supply oil during maintenance, and the lubricating grease of the bearing is also very important. Once the oil and other impurities and moisture are dropped, it will affect the normal swimming. Gap and build the necessary oil film.

    2.1.3 The bearing is used for too long, which exceeds the service life of the bearing and is prone to fatigue of the material. The strong impact of the material causes the material to deform, causing the roller and the raceway surface to peel off and crush, resulting in poor lubrication. And the vibration is increased.

    2.2 Installation impact on bearings

    2.2.1 The inner clearance of the inner ring of the bearing does not match the interference of the shaft. It is also easy to cause bearing failure. The interference is large. It is easy to cause the inner ring of the bearing to crack due to excessive tensile stress. The interference is too small. It is easy to cause the inner ring of the bearing to "relax".

    2.2.2 Bearing assembly with improper clearance, it is easy to cause bearing failure, small clearance is easy to cause friction between the roller and the raceway. As the temperature rises, the bearing inner ring, rolling element, cage, outer ring The temperature of the end caps is not the same, there is a temperature difference between them, so the amount of expansion is also slightly different, which causes a further reduction of the matching clearance, and the heat generation of the bearing is added. If the clearance is too large, the vibration of the roller is increased, which aggravates the impact of the roller and the raceway. At the same time, the internal load distribution is uneven, the load bearing roller is reduced, and the central roller load is excessive.

    2.2.3 When assembling the bearing, the bearing is not impacted by the copper hammer, which causes the cage to be deformed. The inner and outer rings of the traction motor bearing are not installed correctly or other reasons cause the axial traverse amount to disappear, causing the bearing shaft to squash.

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Bearing housing model size

Vertical bearing housing:

SNL vertical bearing housing, large SNL bearing housing, SDG vertical bearing housing, SONL vertical bearing housing, SAF vertical bearing housing, SDAF vertical bearing housing

Integral bearing housing:

SBD vertical bearing, TVN vertical bearing, TN vertical bearing

Flanged housing:

FNL series flanged housing 7225 (00) series flanged housing, I-1200 (00) flanged housing

The bearing size model details table:

Bearing housing model: P305; basic size (mm): 62; weight (kg): 0.90; applicable bearing housing model: UC305;

Bearing housing model: P306; basic size (mm): 72; weight (kg): 1.10; applicable bearing housing model: UC306;

Bearing housing model: P307; basic size (mm): 80; weight (kg): 1.95; applicable bearing housing model: UC307;

Bearing housing model: P308; basic size (mm): 90; weight (kg): 2.20; applicable bearing housing model: UC308;

Bearing housing model: P309; basic size (mm): 100; weight (kg): 3.30; applicable bearing housing model: UC309;
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Radial thrust bearing specification sheet:

GB 273.1 Rolling bearings Tapered roller bearing dimensions;

GB 273.2 Rolling bearings Thrust bearing dimensions scheme;

GB 273.3 Rolling bearings Radial bearing dimensions scheme;

GB 276 rolling bearing deep groove ball bearing dimensions;

GB 281 rolling bearing, self-aligning ball bearing dimensions;

GB 283 rolling bearing cylindrical roller bearing dimensions;

GB 285 rolling bearing double row cylindrical roller bearing dimensions;

GB 288 rolling bearing Spherical roller bearing dimensions;

GB 290 rolling bearing dimensions of drawn cup needle roller bearings;

GB 292 radial bearing angular contact ball bearing dimensions;

GB 294 radial bearing four-point contact ball bearing dimensions;

GB 296 rolling bearing double row angular contact ball bearing dimensions;

GB 296 rolling bearing tapered roller bearing dimensions;

GB 296 rolling bearing flat bottom thrust ball bearing dimensions;
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Bearing maintenance, cleaning, overhaul, lubrication and installation

First, the cleaning of the bearing

When disassembling the lower bearing for inspection, first record the appearance of the bearing, confirm the residual amount of the lubricant, and then wash the bearing after sampling the lubricant for inspection. As a cleaning agent, gasoline and kerosene are commonly used.
The cleaning of the removed bearings is divided into coarse cleaning and fine cleaning. They are placed in the container respectively, and the metal mesh bottom is placed first so that the bearing does not directly contact the container. In rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing and should be noted. In the rough cleaning oil, use a brush to remove the grease and the adhesive. After it is almost clean, it is transferred to the fine wash.
Fine washing is to carefully clean the bearing while rotating it in the cleaning oil. In addition, the cleaning oil should always be kept clean.
Bearing inspection and judgment: In order to judge whether the removed bearing can be used, it should be checked after the bearing is cleaned. Check the raceway surface, the rolling surface, the state of the mating surface, the wear of the cage, the increase of the bearing clearance, and the damage and abnormality that are irrelevant in dimensional accuracy. For non-separable miniature ball bearings, use one hand to support the inner ring horizontally and rotate the outer ring to check if it is smooth.

Separate bearings such as tapered roller bearings can be inspected separately for the rolling surfaces of the rolling elements and the outer ring.

Large bearings cannot be rotated by hand. Pay attention to the appearance of rolling elements, raceways, cages, and ribs. The higher the importance of bearings, the more careful inspection is required.

Second, the lubrication of the bearing

The purpose of bearing lubrication:

The purpose of lubrication of rolling bearings is to reduce internal friction and wear of the bearings, to prevent sticking, and the lubricating effect is as follows.
(1) Reduce friction and wear.
In the mutual contact portion of the ferrule, the rolling element and the retainer constituting the bearing, metal contact is prevented, and friction and wear are reduced.
(2) Extend the fatigue life.
The rolling fatigue life of the bearing is prolonged when the rolling contact surface is well lubricated during rotation. Conversely, if the oil viscosity is low and the thickness of the lubricating oil film is not good, it is shortened.
(3) Discharge friction heat and cool.
The circulation oil supply method or the like can be used to discharge heat generated by friction or heat from the outside to cool. Prevent the bearing from overheating and prevent the lubricant from aging itself.
(4) Others: There are also effects of preventing foreign matter from entering the inside of the bearing or preventing rust and corrosion.

Lubrication method:

The lubrication method of the bearing is divided into grease lubrication and oil lubrication. In order to make the bearing function well, first, choose a lubrication method that suits the conditions of use and the purpose of use. Lubricity of oil lubrication predominates if only lubrication is considered. However, grease lubrication has the advantage of simplifying the structure around the bearing and comparing the advantages and disadvantages of grease lubrication and oil lubrication.

Third, the installation of the bearing:
Whether the bearing is installed correctly affects accuracy, life and performance. Therefore, the design and assembly department should fully study the installation of the bearing. I hope to install according to the operating standards. The items of the job standard are usually as follows:
(1) cleaning the bearing and bearing related components;
(2) Check the size and finishing of the connected components;
(3) installation;
(4) Inspection after installing the bearing;
(5) Supply lubricant.

Generally grease is lubricated, not cleaned, and directly filled with grease. Lubricating oil is not necessary for cleaning. However, for instruments or high-speed bearings, it should be cleaned with clean oil to remove the rust inhibitor applied to the bearing. The bearing with the rust preventive removed is easy to rust, so it cannot be placed. Furthermore, bearings that have been sealed with grease are used without cleaning.

The mounting method of the bearing varies depending on the bearing structure, fit, and conditions. Generally, since the shaft is mostly rotated, the inner ring needs an interference fit. Cylindrical bore bearings, press with multiple presses, or use hot charging methods. For taper holes, mount directly on the taper shaft or with a sleeve.

When installed in the outer casing, the general clearance fits a lot, and the outer ring has an interference amount, which is usually pressed by a press or a cold shrink fit method after cooling. When dry ice is used as the coolant and the shrinkage is installed, the moisture in the air will condense on the surface of the bearing. Therefore, appropriate rust prevention measures are required.
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Analysis of different fault life of linear bearings

Fatigue life: The material of the main moving parts of the linear bearing reaches the limit, resulting in the accumulated time before the linear bearing fails.


Rated dynamic load: The load that a linear bearing can withstand when the service life is 10,000 rpm.


Equivalent dynamic load: The assumed load in which the actual load of the linear bearing is converted in accordance with the operating conditions for determining the dynamic load.


Wear life: The cumulative working time of the linear bearing before it reaches the specified limit due to normal wear. At today's linear bearing industry level, wear life > fatigue life should be used, but in fact traction motors are just the opposite.


Fault life: The cumulative working time before the linear bearing fails and the working capacity is lost.


Service life: It is the above three life-finding formulas. In theory, it refers to the fatigue life of linear bearings. In normal use conditions, it shows the wear life of linear bearings. When the conditions are abnormal and there are no defects in manufacturing, it represents the fault life. .
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Powder metallurgy oil bearing introduction

Powder metallurgy oil-impregnated bearings are generally formed at one time and are basically not machined. The cost is lighter than machining, the material waste is less, the price is therefore cheaper, and it is in line with the current national policy of promoting energy conservation, so it is considered to be a technology that will not fall behind.

The powder metallurgy oil-impregnated bearing has been filled with lubricating oil by vacuum impregnation in the base body, and the lubricating oil will seep out to the running surface due to temperature rise and pumping during operation, so it can be used without additional lubricating oil. The occasion.

Powder metallurgy oil-impregnated bearings (oil-bearing bearings) are a class of porous alloy products impregnated with lubricating oil in the pores. When the shaft rotates, the temperature of the oil-impregnated bearing rises and the pumping action is caused by the friction between the shaft and the oil-impregnated bearing.

The lubricating oil impregnates the friction surface containing the inner or outer diameter of the oil-impregnated bearing when the shaft stops rotating. The lubricating oil is returned to the inside of the oil-impregnated bearing. Therefore, the consumption of lubricating oil is extremely small, and it can be used for a long period of time without supplying lubricating oil from the outside, and is very suitable for the occasion of difficulty in supplying oil and avoiding contamination of lubricating oil.
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Overhaul of machine tool spindle bearings

Determine whether the disassembled machine tool spindle bearing can be reused. Check the machine spindle bearing after cleaning. Carefully check the raceway surface, rolling surface, mating surface condition, cage wear, bearing clearance increase and presence or absence. Damage and abnormality in which the dimensional accuracy is lowered. For the non-separable ball machine spindle bearing, use one hand to support the inner ring horizontally and the outer ring to check whether it is smooth.

Separate machine tool spindle bearings such as tapered roller bearings can be inspected separately for the rolling surfaces of the rolling elements and the outer ring.

Large-scale machine tool spindle bearings can not be rotated by hand, pay attention to check the appearance of rolling elements, raceways, cages, ribs, etc. The higher the importance of machine tool spindle bearings, the more careful inspection is required.

The above is the introduction of the cleaning and overhaul of the spindle bearings of the machine tool, hoping to help you better maintain the bearings and extend the service life of the bearings.
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