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Chuangyuan High-tech shares: How to cool down bearings in mining machinery?

2018-09-07

Overheating bearings are a common and serious fault in mining machinery. If the cause is unknown and not properly handled, it often leads to inefficiency, reduced bearing lifespan, increased repair costs, and even bearing burnout. Therefore, quickly identifying the cause of the fault and taking appropriate measures to resolve it are crucial for ensuring the continuous and safe operation of the equipment.

 

I. Causes of Overheating Bearings

There are many reasons for overheating bearings. The editor of Chuangyuan Gaoxin's Tianjing drilling rig has compiled several common problems:

1. Poor Lubrication

Lubrication significantly impacts bearing lifespan, friction, wear, and vibration. Good lubrication is essential for normal bearing operation. Statistics show that about 40% of bearing damage is related to poor lubrication.

 

 

2. Bearing Wear

Bearings, as crucial components, are used in various machinery of all sizes. Some machinery (e.g., crushers) operate in dusty environments. When fine dust enters the high-speed rotating bearing housing, it causes the lubricating oil or grease inside to deteriorate, leading to poor lubrication and subsequent bearing wear.

Continued operation of a worn bearing increases friction and heat, resulting in a rise in bearing temperature.

 

▲Crusher operating in a dusty environment

 

3. Improper Installation

Improper installation is another major cause of bearing overheating. The correct installation of a bearing directly affects its lifespan and the precision of the main machine. Therefore, during installation, the centerlines of the shaft and bearing bore must coincide.

If the bearing is improperly installed, with low precision and shaft deflection, torque will be generated during rotation, causing bearing overheating or wear. Additionally, the bearing will vibrate, increasing noise and temperature rise.

 

4. Insufficient Cooling

Insufficient cooling typically manifests as clogged pipelines, unsuitable cooler selection, or poor cooling efficiency.

 

 

5. High Vibration

For example, poor coupling alignment, rotor imbalance, poor foundation rigidity, loose foundation bolts, rotating stall, and surge.

 

▲Coupling

 

6. Untimely Inspection and Replacement

If a bearing shows severe fatigue spalling, oxidation, wear pits, cracks, or excessive noise that cannot be adjusted, failure to replace it promptly will cause overheating, unusual noises, and vibrations, affecting normal production.

 

 

Additionally, improper bearing removal, loose equipment foundation bolts causing vibration, can lead to indentations on the bearing raceway and rolling elements, and cracking of the inner and outer bearing rings. Bearings should be inspected at regular intervals during operation.

 

7. Poor Bearing Quality

Rolling bearing components operate under high alternating contact stress with point or line contact. The precision, lifespan, and reliability of the main machine largely depend on the bearings. Therefore, careful inspection is necessary during bearing procurement and acceptance, using qualified and high-quality products from reputable manufacturers.

 

8. Improper Bearing Selection

When selecting bearings, consider their maximum speed and load capacity. Avoid exceeding the speed or load, as this will shorten the bearing lifespan.

 

II. Smart Ways to Cool Down Bearings

When bearing temperature is high, address the problem from the following aspects:

1. Improper oiling; too much or too little lubricating grease:

Regularly lubricate the bearing housing as required. High temperatures can sometimes occur even after oiling, mainly due to over-oiling.

 

▲Insufficient lubricating grease in motor bearings leads to bearing burnout

 

In this case, the temperature continuously rises until a certain point (generally 10℃~15℃ above the normal operating temperature), then remains constant before gradually decreasing.

2. Unsuitable or contaminated grease:

Inappropriate lubricating grease does not easily form a uniform lubricating film, failing to reduce internal bearing friction and wear, resulting in insufficient lubrication and increased bearing temperature.

Mixing different types of grease can cause chemical reactions, leading to grease deterioration, clumping, and reduced lubrication effectiveness.

 

▲Lubricating Grease

 

Contaminated grease also increases bearing temperature. Dust entering during greasing contaminates the grease, causing deterioration and damaging bearing lubrication, leading to increased temperature.

Therefore, use suitable grease, clean the bearing housing and bearings during maintenance, inspect and clear the oiling pipelines, and do not mix different types of grease. When changing to another type of grease, clean the old grease thoroughly. Regularly lubricate during operation and maintenance, and store grease properly to prevent moisture and dust.

3. Insufficient Cooling:

Check for pipeline blockages and whether the inlet and return water temperatures exceed the limits.

If the cooler is unsuitable and the cooling effect is poor, replace it or install a new cooler in parallel if it cannot meet the requirements. For axial flow induced draft fans, check the insulation and sealing of the central tube.

4. If none of the above issues exist, check the coupling:

Coupling alignment must meet process standards. When aligning axial flow induced draft fans and fluid couplings, consider thermal expansion during operation.

Due to thermal expansion, the bearing housing of the induced draft fan impeller side rises; during operation, the fluid coupling temperature increases, causing the bearing housing to expand and the bearing to rise. Therefore, the motor should be higher during alignment, with the allowance determined by the equipment's characteristics and operating temperature parameters.

 

III. What should be paid attention to during bearing inspection?

1. Bearing quality

First, check if the lubricating grease has deteriorated, caked, or contains impurities. This is an important basis for judging the cause of bearing damage.

Second, check whether the bearing is damaged or worn; check the smoothness of the inner and outer rings, rolling elements, and cage surfaces, and whether there are cracks, rust, peeling, pits, overheating discoloration, etc.; measure whether the bearing clearance exceeds the standard; check whether the bushing is worn, pitted, or peeled. If any of the above conditions exist, the bearing should be replaced.

2. Bearing fit

The fit between the inner diameter of the bearing and the shaft, and the outer diameter and the housing during bearing installation is very important. When the fit is too loose, relative sliding will occur on the mating surface, which is called creep.

Once creep occurs, it will wear the mating surface and damage the shaft or housing. Moreover, the wear powder will enter the bearing, causing heat generation, vibration, and damage.

If the interference fit is too large, it will cause the outer diameter of the outer ring to become smaller or the inner diameter of the inner ring to become larger, reducing the internal clearance of the bearing.

To select a bearing suitable for the purpose, the nature, size, temperature conditions, and rotation of the inner and outer rings should be considered.

 

 

3. Adjustment of bearing clearance

If the bearing clearance is too small, the shear friction loss of the grease in the clearance will be too large, which will also cause the bearing to overheat. At the same time, if the clearance is too small, the amount of oil will decrease, and the heat generated by friction will not be able to be taken away in time, which will further increase the temperature rise of the bearing.

However, if the clearance is too large, it will change the dynamic characteristics of the bearing and cause unstable rotor operation. Therefore, it is necessary to select the verified bearing clearance according to different equipment and operating conditions.

Quality wins, innovation leads the future. The above content is compiled and shared by the editor of Chuangyuan Gaoxin Tianjing Drilling Rig. Pictures and texts are from the Internet. If there are any similarities, it is purely coincidental~

Here, Chuangyuan Gaoxin would also like to express our sincere gratitude to every customer who trusts and supports our company. We will strive to repay your love with superior technology, better quality, and better service, contributing our efforts to the success of your business, working together to achieve a win-win situation!

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