Teach you a few practical tips for fault diagnosis of rolling bearings

      Rolling bearings are widely used in equipment. The condition of rolling bearings is directly related to the operating state of rotating equipment. Especially in large-scale continuous production enterprises, it is widely used in important parts of large-scale rotating equipment. Therefore, in actual production, the rolling bearing condition monitoring and Fault diagnosis is an important part of equipment maintenance and management. After long-term practice and exploration, we have accumulated some practical skills for the actual fault diagnosis of rolling bearings.
First, the method and key points of rolling bearing fault diagnosis
A practical method for condition monitoring and fault diagnosis of rolling bearings is vibration analysis.
In practice, you need to pay attention to the location and acquisition method of the measuring point. In order to accurately and accurately reflect the vibration state of the rolling bearing, it must be noted that the collected signal is accurate and true. Therefore, the measuring point should be arranged in the nearest place to the bearing. Generally, there is a rear fan cover at the free end of the motor, and the measuring point is selected in the fan cover fixing screw. Good monitoring results. In addition, it is necessary to pay attention to the multiple acquisition and analysis of the vibration signal, and comprehensively compare. To get an accurate conclusion.



Second, the characteristics of rolling bearings normal operation and practical diagnostic techniques
In the long-term production status monitoring, we found that the rolling bearing showed strong regularity during its use and the repeatability was very good. Normal high-quality bearings are relatively small in vibration and noise at the beginning of use, but the spectrum is somewhat scattered and the amplitude is small, which may be due to some defects in the manufacturing process, such as surface burrs.
After a period of motion, the vibration and noise are maintained at a certain level, and the spectrum is very single, only one or two times the frequency. There are very few spectrums above the power frequency, and the bearing status is very stable and enters a stable working period.
After continuing to run, the bearing vibration and noise begin to increase, and sometimes abnormal sounds occur, but the vibration increase changes slowly. At this time, the bearing kurtness value suddenly reaches a certain value. We believe that the bearing is an initial failure at this time.
At this time, it is required to closely monitor the bearing and pay close attention to its changes. After that, the bearing kurtosis value begins to drop rapidly and approaches the normal value, while the vibration and noise begin to increase significantly, and the increase rate begins to accelerate. When the vibration exceeds the vibration standard (such as ISO2372 standard), the bearing kurtosis value also begins. Rapid increase, when both the vibration standard is exceeded, and the kurtosis value also exceeds the normal value (the available kurtosis is relative to the standard), we believe that the bearing has entered the late fault production, and it is necessary to repair the equipment in time and replace the rolling bearing.
The bearing exhibits late fault characteristics to serious faults (generally bearing damage such as axle hung, burn, sand frame spalling, raceway, bead wear, etc.). The time is not more than one week. The larger the equipment capacity, the faster the speed. The shorter the interval. Therefore, in the actual rolling bearing fault diagnosis, once the late fault characteristics are found, the bearing should be judged decisively and the maintenance should be arranged as soon as possible.

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Technical introduction of high speed spindle bearings for machine tools

Technical introduction of high-speed spindle bearings for machine tools (machine tool bearings):

    Increasing the speed of the spindle bearings is the key to achieving a high-speed, practical spindle. With the development of high speed, it is efficient for machining machine tools. The rolling element is made of ceramic material, the dmN value is about 20×104, and the numerical control machining center with dmN value of 100×104 under grease lubrication condition is increasing day by day. It has become a development trend, and the oil and oil mist lubrication method will become the future. The development direction of high-speed machine tool spindle bearing lubrication.

    1 high-speed spindle bearing development:

    Generally, angular contact ball bearings with excellent rigidity and high speed performance are used, in order to meet the high speed requirements of the machine tool spindle. Secondly, cylindrical roller bearings are used.

    The dmN value under grease lubrication conditions is 50×104 or less. After the development of oil and gas lubrication, at the same time, gradually develop a compatible lubrication system. From the dmN value of the high-speed performance of the spindle bearing (dm is the diameter of the bearing pitch circle mm × N is the speed r / min. The dmN value has reached 100 × 104 or more. Later, in the bearing, the angle of the rolling element is ceramic Contact ball bearings, after the dmN value of 200 × 104 × 90 years developed spray lubrication, dmN value can reach 300 × 104.

    2 high speed spindle bearing technology:

    (1) High-speed angular contact ball bearings:

    Single row and double row cylindrical roller bearings are inferior to angular contact ball bearings in terms of high speed performance. Angular contact bearings are bearings with contact angles, and tapered roller bearings can be seen. The larger the contact angle, the better the axial stiffness, but since the gyro sliding and the spin sliding between the ball and the raceway are also large, the heat is also increased. In order to improve the speed performance, the method is to reduce the size (or mass) of the ball to change the curvature coefficient of the channel, to reduce the centrifugal force of the ball, reduce the internal load generated during high-speed operation, and increase the number of balls to increase the rigidity.

    (2) Ceramic ball angular contact ball bearings:

    Hybrid ceramic ball bearings with silicon nitride (Si3N4) ceramics for rolling systems have been introduced, in order to reduce the ball quality and increase the speed. Performance comparison

    As a high-speed spindle bearing material, ceramic (Si3N4) has the following advantages: the rolling element generates small centrifugal force and is light in weight when rotating at high speed. Because the density is smaller than the bearing steel. The rotational torque can be reduced, thus reducing the temperature rise and increasing the life. Good thermal conductivity makes it difficult for the rolling elements of ceramic materials to adhere to metals at high speeds. Burns and burns occur when lubrication conditions are good. The thermal expansion is small, and when the rolling elements are in contact with the inner ring, the pre-tightening force is less likely to occur and the clearance is reduced. The deformation of the bearing is small due to high hardness and good rigidity. The rigidity of the spindle is also improved. In summary, therefore, the ceramic material (Si3N4) is used as the rolling element, and the speed can be increased by about 25% and the life of the bearing steel rolling body can be increased by about 3 times.

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