Reason analysis and treatment measures for high bearing temperature

     This paper analyzes several reasons for the high bearing temperature of boiler rotating equipment in thermal power plants, and proposes corresponding preventive measures. High bearing temperature is a common and harmful fault of rotating equipment, which will reduce the service life of the bearing and increase the maintenance cost. When the temperature rises faster and the temperature exceeds the standard, it will easily lead to unplanned outage or reduced load operation. The economic benefits have a great impact. Therefore, it is the guarantee for the continuous and safe operation of the equipment to quickly determine the cause of the fault and take appropriate measures to solve it.

1 Common causes of excessive bearing temperature

1) Poor lubrication, such as insufficient lubrication or excessive lubrication, the quality of the lubricant does not meet the requirements, deterioration or debris;
2) insufficient cooling, such as blockage of the pipeline, improper selection of the cooler, and poor cooling effect;
3) Abnormal bearing, such as bearing damage, poor bearing assembly process, gap adjustment of each part of bearing housing does not meet the requirements;
4) The vibration is large. If the coordinating process of the coupling does not meet the requirements, the rotor has dynamic and static imbalance, the basic rigidity is poor, the ground is weak, the rotation stalls and the surge.

2 solutions

When the bearing temperature is high, the problem should be solved from the following aspects:
1) The amount of oil added is not appropriate, and the grease is too little or too much. The bearing housing should be refueled regularly as required by the job. After the bearing is refueled, sometimes the temperature will be high, mainly due to excessive refueling. At this time, the temperature continues to rise. After reaching a certain point (generally about 10 ° C ~ 15 ° C higher than the normal operating temperature) will remain unchanged, and then gradually decline.
2) The grease added to the bearing does not meet the requirements or is contaminated. The lubricating grease is not suitable for selection, and it is not easy to form a uniform lubricating oil film. The internal friction and wear of the bearing cannot be reduced, the lubrication is insufficient, and the bearing temperature is increased. When different types of grease are mixed, a chemical reaction may occur, causing the grease to deteriorate and agglomerate, reducing the lubricating effect. The contamination of the grease will also increase the temperature of the bearing, and the dust will fall into the process of adding grease, causing oil contamination, resulting in deterioration of the grease inside the bearing housing, which will damage the bearing lubrication and increase the temperature. Therefore, suitable grease should be selected. The bearing box and bearing should be cleaned during maintenance, and the fueling pipeline should be checked and unblocked. Different types of grease should not be mixed. If other types of grease are replaced, the original grease should be cleaned first; Add grease regularly, and grease should be properly stored to prevent moisture and dust.
3) Cooling is not enough. Check if the pipeline is blocked, whether the inlet temperature and return water temperature exceed the standard. If the cooler is not suitable for use and the cooling effect is poor and cannot meet the requirements for use, it should be replaced in time or a new cooler installed in parallel. The axial flow induced draft fan should also check the insulation and sealing of the core barrel.

For more information and purchase please visit: https://www.supplyforever.com

Introduction to the cause of failure of sliding bearings

    Imported bearings will always encounter some technical problems in the use and purchase. Today, the technicians of Tianjin Jiarui Yiye Bearing Co., Ltd. will explain the reasons for the failure of sliding bearings.
1. Material and blank manufacturing factors
(1) poor adhesion between the liner and the backing
This is a major problem with sliding bearings that cast tin-based or lead-based bearing alloy liners. A good combination enhances the tin-based and lead-based bearing alloys and contributes to heat dissipation from the bearing surface. For good bonding, tin must be placed on the backing joint before casting the tin-based and lead-based bearing alloys, and the temperature of the backing and bearing alloys is strictly controlled.
When the size of the bearing bush is allowed, the tin bath method should be used to hang the tin. The temperature of the tin bath in the pure tin bath should be kept at 280-300 ° C. The temperature of the tin bath in the solder bath should be kept at 270-300 ° C. The bush is immersed in the tin bath. The temperature can reach the tin liquid temperature and can be taken out. Large bushings can be tinned by tinning, first heating the bush with flame, and then applying pure tin or solder to the surface to be tinned.
It has been found that making a wedge groove on the surface of the backing cast lining not only does not contribute to the combination of the backing and the lining, but at the sharp corners of the shoulder of the groove, stress concentration will cause cracks.
(2) stomata
For large bushings with tin-based or lead-based bearing alloy linings, when the casting temperature is too low or the backing is insufficiently preheated, air bubbles will appear on the lining joint surface. These bubbles are not conducive to heat dissipation from the surface of the bearing pad and also weaken the tin- or lead-based bearing alloy lining. When casting a cast copper-based alloy, looseness is caused by the release of hydrogen from the copper alloy.
(3) Large grain size
This is a peculiar problem for tin-based and lead-based bearing alloy liner bushings. In the cooling and solidification process of the cast bearing alloy, if the cooling rate is very slow, the size of the tin-bismuth crystal grains will exceed 0.1 mm, which can be observed by the naked eye. Such intermetallic compounds are easily broken, break off the friction surface after being broken, and become particles entering the lubricating oil circulation system, causing bearing damage.
(4) Uneven distribution of lead
Copper and lead are not co-dissolved, so when the bearing bush is made of copper-lead alloy which is a copper-based bearing alloy, uneven distribution of lead may occur. Rapid cooling of the copper-lead alloy after casting can prevent uneven distribution of lead. The production of copper-lead alloy bearing bush by powder metallurgy can completely solve the problem of uneven distribution of lead in copper-lead alloy.
2. Installation and operation factors
(1) Poor alignment
The support of the shaft requires at least two fulcrums. If the two sliding bearings are poorly aligned and the coaxiality error is large, the distribution of the load on the width of the bearing bush will be uneven, and the edge contact phenomenon will occur, causing the lubricating oil film to rupture and causing adhesive wear.
(2) improper matching of bearing bush and bearing housing hole
If the bearing bush is improperly fitted with the bearing housing hole, the bearing bush may be loose and cause fretting wear. After loose or fretting wear, it is unfavorable for heat transfer, which may cause the friction surface temperature of the bearing pad to be too high.
The mating surface of the bearing bush and the bearing housing is not clean, and there are particles and dirt, which will also cause poor conduction.
In summary, checking the damaged bearing surface may provide important information about bearing failure, so you should not forget to check the back of the bearing.

For more information and purchase please visit: https://www.supplyforever.com