Common Fault Diagnosis of Self aligning Roller Bearings in Cement Equipment

Self aligning roller bearings are a very important rotating component in cement equipment, and are also a major source of cement equipment. This article mainly elaborates on the diagnostic methods for common faults of self-aligning roller bearings in cement equipment, and further analyzes their practical skills. Through practice, it has been proven that these methods are very simple and easy to use in the use and maintenance of cement equipment, and also reflect good economic efficiency in the use process.

In cement equipment, self-aligning roller bearing is a very important rotating part, and also a main source of cement equipment. To some extent, the good operation status of self-aligning roller bearings is directly related to the performance of the entire equipment.

On the whole, the self-aligning roller bearing is a very precise part in the machine. Usually, the tolerance of self-aligning roller bearings is controlled within about one tenth of the tolerance of other components. However, a large number of practical studies have shown that less than 10% of bearings can reach their theoretical operating life. Among them, 40% of bearings fail mainly due to lubrication problems, while 30% fail due to jamming or incorrect assembly errors. In addition, Another 20% of the failures are caused by manufacturing defects or overload usage. There are many cases of equipment failures caused by early failures of self aligning roller bearings in cement machinery equipment.

So, in our work, we must promptly detect faults, actively search for the root causes of faults, and then eliminate them through corresponding remedial measures. This is the key to ensuring the normal operation of the equipment. The fault diagnosis technology and dynamic monitoring technology for self-aligning roller bearings can detect potential faults as early as possible during use, while also improving the performance and management level of the equipment. The economic benefits in actual use are very significant. Based on the above background, this paper further analyzes and discusses the practical skills of fault diagnosis and treatment of self-aligning roller bearings in cement equipment. Now let's enter into the discussion of this paper.

Typical fault analysis

As for self aligning roller bearings, their early failures mainly include peeling, cracking, and dents of the rollers and raceways. The main reasons for these faults are careless handling, inadequate installation, and tilting of bearings. Generally speaking, the main mode of failure of self-aligning roller bearings in cement equipment is simple fatigue peeling caused by rolling contact. The peeling surface area is approximately 2mm2 and the depth is approximately 0.2-0.3mm. Its surface area and depth can be determined by monitoring instrument vibration. This peeling may occur on the outer ring, inner ring, and rolling element, among which the inner ring has a relatively high contact stress, so the possibility of fracture is greater.

Causes and Treatment of Oil Leakage in Motor Self aligning Roller Bearings

High power motors frequently experience oil leakage during use, particularly in the structure of self-aligning roller bearings. During maintenance and repair, the possible causes of oil leakage in the motor were analyzed and the following solutions were proposed.

1. The pressure difference between the inside and outside of the self-aligning roller bearing is large. Forced lubrication of the bearing pads, the lubricating oil itself has a certain pressure, and during the operation of the shaft, the oil will generate bubbles, resulting in a certain pressure. When the motor is running, a certain negative pressure will be generated due to the action of the fan, which increases the pressure difference inside and outside the oil chamber, leading to oil leakage. In order to balance the pressure difference inside and outside the oil chamber, a ventilation pipe is installed between the oil chamber and the outside to balance the pressure difference. However, during use, blockage may occur, causing an increase in pressure inside the oil chamber and causing oil leakage.

Solution: Regularly check if the balance pipe is loose and clean the fuel tank vent pipe in a timely manner.

2. Improper adjustment of oil pressure leads to poor oil return. High or low oil pressure can cause poor oil return. The oil pressure is too low, causing the oil to stay in the oil chamber for too long, causing the temperature to rise during the operation of the shaft, resulting in oil mist and high pressure; If the oil pressure is too high, it will result in insufficient oil return capacity, resulting in excessive oil storage in the oil chamber and an increase in internal pressure due to the high oil level.

Solution: Adjust the forced lubrication pressure to 0.1~0.8MPa, so that the oil level in the oil chamber is at the position of 1/2~1/3 of the sight glass, and it is advisable to keep the return oil unobstructed.

3. Unreasonable design of the return oil pipeline can also lead to poor return oil and increase the pressure in the oil chamber. Impurities in the return oil pipeline or unclean cleaning in the pipeline can lead to clogging of the filter, resulting in poor return oil.

Solution: The oil chamber outlet of the return pipeline should be on the same level as the oil inlet, and the entire return pipeline should be tilted at a 15 ° angle to the return tank, so that the return pipeline can naturally return oil. At the same time, the filter and the entire lubricating oil pipeline should be cleaned regularly.

4. The contact surface between the floating palace and the shaft is severely worn due to prolonged friction, resulting in excessive clearance between the palace and the shaft; The elastic coefficient of the fixed spring of the floating palace seal changes, causing the floating palace seal to loosen and leading to an increase in clearance.

Solution: Regular inspection and timely replacement.

5. The wear of the contact surface between the sealing oil baffle and the shaft causes excessive clearance; The return oil hole in the sealed oil baffle is too small or blocked by impurities, which cannot meet the actual return oil volume.

Solution: Replace the sealing oil baffle and modify it. Change the material of the contact surface between the sealing oil baffle and the shaft to wear-resistant material; Increase the oil return hole to meet the actual oil return needs (not too large).

6. During the installation process of self-aligning roller bearings, the sealing between the upper and lower bearing covers of the bearing box was not properly handled between the sealing oil baffle and the oil chamber; Long term operation leads to loosening of fastening bolts, aging and deterioration of sealant, resulting in poor sealing.

Solution: During the reinstallation process, use high-performance and reliable sealant on the contact surface, and apply evenly and appropriately. During the second reinstallation, it is necessary to clean the original sealant before applying new sealant.

7. The change of oil quality causes more and more foam in the oil. In the whole lubrication system, foam occupies more operating space, which leads to the increase of oil pressure in the oil chamber, and the large pressure difference leads to the oil escaping from the shaft gap in contact with the floating palace seal and seal oil baffle.

Solution: Regularly inspect and analyze the lubricating oil, and replace it promptly if there are any problems with the oil quality.

The cause analysis and solution of oil leakage in the above-mentioned motor self aligning roller bearing have achieved certain results in practical application, ensuring the safe and stable operation of the unit.

What are the consequences of improper bearing heat treatment

1. Heat treatment deformation

During heat treatment of self-aligning roller bearing parts, there are thermal and structural stresses, which can overlap or partially cancel each other. This is complex and variable because it can change with changes in heating temperature, heating speed, cooling method, cooling speed, part shape and size, so heat treatment deformation is inevitable. Understanding and mastering its variation patterns can make the deformation of self-aligning roller bearing parts (such as the ellipticity of the ring, size increase, etc.) within a controllable range, which is conducive to production. Of course, mechanical collisions during heat treatment can also cause deformation of the parts, but this deformation can be reduced and avoided through improved operations.

2. Overheating

Overheating of the microstructure after quenching can be observed on the rough surface of the self-aligning roller bearing parts. But to accurately determine the degree of overheating, it is necessary to observe the microstructure. If coarse needle like martensite appears in the quenched structure of GCr15 steel, it is considered as a quenched overheated structure. The cause of formation may be comprehensive overheating caused by excessive quenching heating temperature or prolonged heating and insulation time; It may also be due to the severe banded carbides in the original structure, which form local martensite needle like coarseness in the low-carbon zone between the two bands, resulting in local overheating. The residual austenite in the overheated structure increases and the dimensional stability decreases. Due to the overheating of the quenched structure and the coarsening of the steel crystals, the toughness and impact resistance of the parts will decrease, and the service life of the self-aligning roller bearings will also be reduced.

3. Underheating

If the quenching temperature is too low or the cooling is poor, it will produce a martensite structure in the microstructure that exceeds the standard requirements, called undercooled structure. It causes a decrease in hardness, a sharp decrease in wear resistance, and affects the service life of self-aligning roller bearings.

4. Soft spots

The phenomenon of insufficient local hardness on the surface of self-aligning roller bearing parts caused by insufficient heating, poor cooling, and improper quenching operation is called quenching soft spots. It can cause a serious decrease in surface wear resistance and fatigue strength, just like surface decarburization.

5. Surface decarburization

During the heat treatment process of self-aligning roller bearing parts, if heated in an oxidizing medium, the surface will undergo oxidation, reducing the mass fraction of carbon on the surface of the parts and causing surface decarburization. If the depth of the surface decarburization layer exceeds the final machining allowance, the part will be scrapped. The determination of the depth of surface decarburization layer can be done using metallographic and microhardness methods in metallographic examination.

6. Quenching cracks

The cracks formed by internal stress during the quenching and cooling process of self-aligning roller bearing parts are called quenching cracks. The reasons for this type of crack are: due to high quenching heating temperature or rapid cooling, the thermal stress and the structural stress caused by changes in metal mass volume are greater than the fracture strength of the steel; The original defects on the working surface (such as surface microcracks or scratches) or internal defects in the steel (such as slag inclusion, severe non-metallic inclusions, white spots, shrinkage residue, etc.) form stress concentration during quenching; Severe surface decarburization and carbide segregation; Insufficient or delayed tempering of parts after quenching; The previous process caused excessive cold stamping stress, forging folding, deep turning tool marks, sharp edges and corners of oil grooves, etc.