There has been the failure of rolling mill bearings in recent years. Engineers are also looking for the reason, but they have not found it. And properly block sundries and moisture, indicating that the oil seal should not be worn However, when opening the bearing housing, check the bearing and regularly check the oil seal Check the condition of the oil seals near the high temperature bearing to ensure that they are sufficient to prevent hot or corrosive liquid or gas from penetrating the bearing along the axis.
Generally, the temperature of NTN bearing starts to rise slowly with the operation of the bearing and reaches a stable state after 1-2 hours. The normal temperature of rolling mill bearing varies with the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are appropriate, the bearing temperature will rise sharply and abnormal high temperature will occur. At this time, the operation must be stopped and necessary preventive measures must be taken.NTN Clutch Bearing over Temperature leads to Common Failure Modes
The 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 the occurrence of combustion shaft accident.NTN Clutch Bearing over Temperature leads to Common Failure Modes
High temperature often indicates that NTN bearing is in abnormal condition. High temperature is also harmful to the lubricant of rolling mill bearings. Sometimes bearing overheating can be attributed to the lubricant of the bearing. If the temperature of the bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, bearing ring damage, insufficient clearance, high friction caused by oil seal, etc.NTN Clutch Bearing over Temperature leads to Common Failure Modes
Therefore, it is necessary to continuously monitor NTN bearing temperature, whether it is measuring the rolling mill bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a fault has occurred.NTN Clutch Bearing over Temperature leads to Common Failure Modes
In fact, the bearing faults we analyzed before are not so possible. High temperature is also harmful to the lubricant in the bearing. Sometimes the overheating of the bearing can be attributed to the lubricant of NTN bearing. If the bearing operates for a long time at a temperature of more than 125 ℃, the service life of high-temperature bearing will be reduced. The reasons for high-temperature bearing include insufficient or excessive lubrication, magazine contained in the lubricant, excessive load, damage of rolling mill bearing and insufficient clearance, And high temperature friction caused by oil seal, etc. Well, let’s summarize these. If you are incomplete, we can only say so much about the failure of NTN bearing.
The serious damage of NTN bearing is often not caused by a single reason, but under the combined action of several aspects, a vicious cycle occurs under bad operating conditions, resulting in the serious burning loss of clutch bearing. Therefore, after the accident, it is often difficult to judge the cause, which brings some difficulties for us to formulate relevant measures. For the convenience of discussion, first analyze the causes of bearing failure from several aspects.
NTN Clutch Bearing over Temperature leads to Common Failure Modes
(1). Check whether the cooling water pressure, water flow and pipeline system are normal. If the water pressure is low, the filter may be blocked and cannot be handled in time, it can be shut down for treatment. When it is confirmed that it can work, it can be put into use.NTN Clutch Bearing over Temperature leads to Common Failure Modes
(2). Check the oil pressure of the governor. If the oil pressure is low, the cooling water hydraulic valve may be closed.
(3). Check NTN bearing for abnormal sound, and check whether the swing of clutch bearing is abnormal.
(4). Take an oil sample to observe whether the oil color has changed, and test to see whether it has deteriorated. If the deterioration is confirmed, stop the machine and replace it with new oil.
(5). Check whether the oil level of the oil gauge is normal. If not, check whether the oil drain valve of the oil tank is tightly closed. If it has been closed tightly, oil shall be added. If it is oil leakage from the sealant pad, it shall be shut down for treatment.NTN Clutch Bearing over Temperature leads to Common Failure Modes
Contact fatigue failure refers to the failure of the working surface of the clutch bearing under the action of alternating stress. Contact fatigue spalling occurs on the working surface of NTN bearing, which is often accompanied by fatigue cracks. It first occurs from the large alternating shear stress below the contact surface, and then extends to the surface to form different spalling shapes, such as pitting or pitting spalling, which is called shallow spalling. Due to the gradual expansion of the spalling surface, it often expands to the deep layer, forming deep spalling. Deep spalling is the fatigue source of contact fatigue failure.
Wear failure refers to the failure caused by the continuous wear of the metal on the working surface caused by the relative sliding friction between the surfaces. Continuous wear will cause NTN bearing parts to be damaged gradually, and eventually lead to the loss of dimensional accuracy of clutch bearing and other related problems. Wear may affect the change of shape, the increase of fit clearance and the change of working surface morphology, may affect the lubricant or make it polluted to a certain extent, resulting in the complete loss of lubrication function, so that the bearing loses the rotation accuracy and even cannot operate normally. Wear failure is one of the common failure modes of various bearings. According to the wear form, it can be divided into common abrasive wear and adhesive wear.