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Why is the bearing

In production, there is often a fever of rolling bearings. If the cause analysis is not clear, the treatment is not timely and the measures are inappropriate, it will take twice the effort and half the effort, and even lead to bearing burnout, gear reducer teeth beating and other malignant accidents.



Following are some typical cases encountered in the process of production debugging. The specific problems in design, installation, lubrication, assembly and other links are analyzed and summarized for your reference.




Bearing fever caused by improper lubrication


1. There are congenital deficiencies in the design of bearing lubrication parts.


The excess fan of No. 1 kiln head of ZB Company had many bearing burning accidents in 2003 (the initial stage of commissioning). After on-site investigation, it was found that there was a problem in the oil mark design of bearing seat.


When the oil level is marked under the oil mark, the actual measurement shows that the lowest row of balls of the bearing has just touched the oil level. Only when the oil level is displayed on the upper scale line, can it meet the operation needs.


When the oil level approached the lower groove, the lubrication condition deteriorated. At first, the bearing temperature increased slowly. The field personnel did not pay enough attention to the alarm of bearing fever. Once the temperature rose to a certain extent, the bearing would rise sharply and burn out in a very short time. Therefore, incorrect oil labeling will cause misleading to inspection and maintenance personnel. After ascertaining the reasons, the refueling standard line was redrawn.


Another example is the high-speed shaft bearing of CL rotary kiln reducer, which smokes suddenly only 2-3 hours after starting up. The reason for the accident is that the return hole in the bearing seat of the high-speed shaft is too low, and most of the oil coming from the oil pipe flows directly from the return hole into the reducer. The angle of oil return hole is adjusted to keep a certain oil level in the bearing seat, and the operation is normal.


2. Lubricating oil pipes are blocked by foreign bodies


Because the lubrication management is not strict, containers are dirty or pipeline welding pickling is not standardized in the process of oil refueling and oil changing, which results in impurities such as welding slag rust entering the pipeline and then blocking the oil hole, which is quite common in earlier projects.


For example, ZB's raw material mill reducer is blocked by burning bearings, TH's cement mill reducer is also blocked by cotton yarn, resulting in long-term high temperature bearings. In particular, TH company reducer high-speed axle bearing inspection oil volume, always can not see how much oil can be added to the high-speed bearing, etc. After thorough removal of the tubing with high-pressure air blowing, it was found that there were two fine cotton ropes blocked inside!


In addition, TH company also found that the oil hole of the eccentric sleeve of the bearing was too thin (the oil hole of the eccentric sleeve could be one size larger than the oil hole diameter of the bearing itself), so the oil hole was enlarged.


Because the bearings of all parts of the hard tooth surface reducer are generally forced lubricated by dilute oil station, and the oil pipes at each lubrication point are in parallel, it is difficult to find the blockage phenomenon of individual oil pipes when observing the total amount of oil and return oil. Therefore, the experienced maintenance personnel will carefully check the temperature of each oil pipe and judge it according to the temperature difference of the oil pipes. Is the oil pipeline unblocked? Generally, the temperature of oil-free tubing is lower than that of other pipelines.


The inspectors of PY Company have found that the temperature of the oil pipe of the high speed axle of the reducer in the kiln is low, and finally confirmed the serious hidden danger of the oil pipe blockage, thus avoiding a major accident.


3. Lubricating oil (grease) deterioration or improper refueling


The lubricating oil (or grease) used in rolling bearings has a certain working temperature. When the temperature is too high, the water and ash in the bearing seat will be seriously oxidized, emulsified and other deterioration, thus losing the lubrication effect and burning the bearing due to high temperature. In addition, the poor quality of lubricating oil (or grease) itself or the lack of timely refueling (grease) in operation are also common phenomena, such as rainwater entering into the roller bearing of belt conveyor, coal or raw meal entering into the bearing of rotary feeder and Fuller pump, which will cause the bearing temperature to rise or produce abnormal sound.


4. Scaling and clogging of coolers in lubricating pipelines, resulting in poor cooling effect


Especially in summer production, this problem is particularly prevalent. Individual manufacturers do not hesitate to increase or parallel series coolers to enhance the cooling effect. Because the scaling of high temperature fan cooler is serious, bearing temperature is too high frequency and frequent alarm has been encountered in various branches. The more effective treatment method is acid cleaning and scale removal of the cooler before summer every year.


Bearing heating caused by improper installation




1. Bearing fever caused by insufficient design expansion


This kind of situation is easy to occur in the large-scale fan and crusher and other long-axis equipment, which is also a link that the equipment design, manufacture and installation and maintenance personnel are easy to overlook.


Typical case CX company's rotary kiln rear exhaust fan, in the initial stage of commissioning, there was a severe heating phenomenon of the free-end bearing of the fan. Because the thermal expansion of the rotor spindle and the end cover of the bearing occur severe friction, the high temperature generated in a very short period of time will weld the end cover of the bearing seat and the end face of the rotor spindle together.


Therefore, during the installation and acceptance of fresh air fans, attention should be paid to the calculation of whether the axial clearance of bearings at the free end can meet the expansion requirements of working conditions.


The method for calculating the expansion of axes is simple:

Delta L = L * (t-t0) * 0.000012

Formula:Delta L - axis expansion; mm;

Length of shaft between L-bearing seat; mm;

T-working temperature;

T0 - The environmental temperature when the equipment is installed;


It should be pointed out that the shrinkage of equipment in winter should also be considered when installing in summer, which should be paid special attention to in northern areas. Generally speaking, the maximum ambient temperature difference between winter and summer in cold areas in the north can reach 80 C. If the axis with length of 3 m is installed in summer, the maximum contraction in winter (when shutdown) can be connected.


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