Sometimes your bearings get hot, which may not necessarily be a bearing problem but also a machine problem.
Alright, let's get back to the topic.
High bearing temperature is a common and dangerous failure of rotating equipment that can reduce bearing life and increase maintenance costs.
When the temperature rises rapidly and exceeds the limit, it can cause unscheduled outages or load-shedding operations of the unit, which can have a significant impact on economic efficiency.
Therefore, it is necessary to quickly determine the cause of the failure and take appropriate measures to resolve it to ensure the continued safe operation of the equipment.
Today I will help you analyze the causes and solutions for enduring the heat.
01. Common causes of high bearing temperatures
- Poor lubrication, such as insufficient or excessive lubrication, lubricating oil quality that does not meet requirements, deterioration or contamination.
- Insufficient cooling, such as blocked pipes, improper cooler selection, or poor cooling effect.
- Bearing abnormalities such as bearing damage, improper bearing assembly process, or bearing housing clearance adjustment that does not meet requirements.
- Large vibration, such as poor coupling alignment process that does not meet requirements, rotor with dynamic and static imbalances, low foundation stiffness, virtual feet and rotational stall and oscillation.
02. When the bearing temperature is high, the problem should be solved first from the following aspects
1 . Inadequate refill quantity, too little or too much lubricating grease
The bearing housing must be lubricated regularly according to job requirements.
After lubricating the bearing, sometimes the temperature increases due to over lubrication. The phenomenon is that the temperature continues to rise, and after reaching a certain point (generally about 10°C to 15°C above the normal operating temperature), it will remain constant and then gradually decrease.
two . Grease added to the bearing does not meet the requirements or is contaminated
If the selection of lubricating grease is inappropriate, it is difficult to form a uniform lubricating film, which cannot reduce the internal friction and wear of the bearing.
If lubrication is insufficient, the bearing temperature will increase.
When different types of grease are mixed, a chemical reaction can occur, causing the grease to deteriorate, harden and reduce lubrication.
Contaminated grease will also increase bearing temperature.
The dust that falls in the process of adding grease causes grease pollution, resulting in the deterioration of the grease inside the bearing housing, destroying the bearing lubrication and increasing the temperature.
Therefore, the appropriate grease must be selected, the bearing housing and bearing must be cleaned during maintenance, and the pipeline must be checked for blockages.
Different types of grease must not be mixed.
If replacing other types of grease, the original grease must be cleaned first. Grease must be added regularly during operation and maintenance.
Grease must be stored properly and protected from moisture and dust.
3 . Insufficient cooling
Check whether the piping is blocked and whether the oil inlet and return water temperatures exceed the standard.
If the refrigerator is unsuitable, the cooling effect is poor and does not meet the usage requirements, it must be replaced or a new refrigerator must be installed in parallel.
Also, check the insulation and sealing of the axial flow pilot fan center cylinder.
4 . Check the alignment of the coupling and bearings after confirming that there is no such problem
Coupling alignment must meet process standards. Thermal expansion of equipment in operation must also be considered when aligning axial flow fans, hydraulic couplers, etc.
Due to thermal expansion on the induced draft fan side, the bearing housing temperature increases.
As the temperature of the hydraulic coupling increases during operation, the bearing housing expands and the bearing temperature increases.
Therefore, when aligning, the engine must be larger, and the size of the reserved quantity depends on the characteristics of the equipment and the operating temperature parameters.
03. Bearing inspection
1 . Bearing quality
When disassembling the bearing box, the first step is to check whether the lubricating grease is deteriorated, hardened, contains impurities or presents any other undesirable conditions. This is an important basis for determining the cause of bearing damage.
Next, check the bearings for bite marks and wear, and examine the surface finish of the bearing inner and outer rings, rolling elements, and cages for cracks, rust, peeling, holes, overheating, discoloration, or any other defects. .
Check whether the bearing clearance exceeds the standard and check the bushing for signs of wear, corrosion or peeling. If any of these problems are found, it is necessary to replace the bearings with new ones.
two . Bearing coordination
When installing a bearing, it is crucial to ensure that the bearing's inner diameter properly matches the shaft, as well as the outer diameter and housing.
If the fit is too loose, it can result in a phenomenon known as creep, where there is relative slippage between the mating surfaces.
This deformation will eventually cause wear on the mating surfaces, which can cause damage to the shaft or housing, as well as the accumulation of wear debris inside the bearing. This, in turn, can cause heat build-up, vibration and, ultimately, destruction.
On the other hand, if the interference is too large, it may cause the outer diameter of the outer ring to shrink or the inner diameter of the inner ring to expand, reducing the bearing's internal clearance.
When selecting the fit for a specific application, several factors must be taken into consideration, including the nature and size of the bearing load, temperature conditions, and the rotation of the inner and outer rings.
3 . Adjusting the adjustment clearance of each part of the bearing
If the bearing clearance is too small, this can lead to excessive grease loss through shear into the clearance, resulting in the bearing heating up.
Furthermore, a small gap reduces the volume of oil available, making it difficult to dissipate the heat generated by friction, leading to an increase in bearing temperature.
On the other hand, having too much play can change the dynamic behavior of the bearing and cause the rotor to operate unstable.
Therefore, it is important to choose the appropriate and verified bearing clearance for different equipment and operating conditions.
