1. Vibration of SKF bearings
SKF bearing vibration is very sensitive to bearing damage, such as peeling, indentation, rust, cracks, wear, etc., will be reflected in the bearing vibration measurement, so it can be measured by using a special bearing vibration measurement device (frequency analyzer, etc.) The magnitude of the vibration cannot be inferred from the specific abnormality by frequency. The measured value is different due to the use condition of the bearing or the installation position of the sensor, so it is necessary to analyze and compare the measured value of each machine in advance to determine the judgment standard.
2. SKF bearing temperature
The temperature of SKF bearings can generally be inferred from the temperature of the outer surface of the bearing. It is more appropriate if the oil hole can be used to directly measure the temperature of the outer ring of the bearing.
Normally, the temperature of the bearing starts to rise slowly as the bearing runs, and reaches a stable state after 1-2 hours. The normal temperature of the bearing varies with the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are proper, the bearing temperature will rise sharply and abnormally high temperature will occur. At this time, the operation must be stopped and necessary precautions must be taken.
The use of a thermal sensor can monitor the working temperature of the bearing at any time, and automatically alarm or stop when the temperature exceeds the specified value to prevent combustion shaft accidents.
High temperature often indicates that the bearing is in abnormal condition. High temperature is also harmful to the lubricant of the bearing. Sometimes bearing overheating can be attributed to the lubricant of the bearing. Long-term continuous rotation of bearings at temperatures exceeding 125°C will reduce bearing life. Causes of high temperature bearings include: insufficient or excessive lubrication, lubricants. Containing impurities, excessive load, bearing ring damage, insufficient clearance, and high friction caused by oil seals, etc.
SKF bearings show strong regularity during their use and have very good repeatability. Normal high-quality imported bearings (rolling bearings) have relatively small vibration and noise at the beginning of use, but the frequency spectrum is somewhat scattered and the amplitude is small, which may be caused by some defects in the manufacturing process, such as surface burrs.
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After a period of exercise, vibration and noise maintain a certain level, and the frequency spectrum is very single, with only one or two octave frequencies. There is rarely a frequency spectrum above three times the power frequency, and the bearing state is very stable, entering a stable working period.
After continuing to run and entering the later stage of use, SKF bearing vibration and noise begin to increase, and sometimes abnormal sounds appear, but the increase in vibration changes slowly. At this time, the bearing kurtosis value suddenly reaches a certain value. We believe that at this time, SKF bearings are manifested as initial failures.
Therefore, continuous monitoring of bearing temperature is necessary, whether it is measuring the bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a malfunction has occurred.
At this time, it is required to conduct close monitoring of the SKF imported bearings and pay close attention to their changes. After that, the bearing kurtosis value began to drop rapidly and approached the normal value, while the vibration and noise began to increase significantly, and the increase rate began to accelerate. When the vibration exceeded the vibration standard (such as the ISO2372 standard), the bearing kurtosis value also began Rapid increase. When both the vibration standard and the kurtosis value exceed the normal value (the available kurtosis is relatively standard), we believe that the bearing has entered the late stage of failure production, and the equipment needs to be repaired and replaced in time.
SKF bearings show late failure characteristics to serious failures (usually bearing damage such as shaft holding, burns, spalling of the sand frame, 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 time. Therefore, in the actual fault diagnosis of SKF bearings, once the late fault features are found, the bearing should be determined decisively and repaired as soon as possible.