Abstract: Sliding bearings are very important components of blast furnace blower units, and improper installation, maintenance, and operation may cause sliding bearing failures. This article mainly discusses the causes of sliding bearing failures in blast furnace blower units and proposes preventive measures that should be taken during installation, maintenance, and operation.

Keywords: blast furnace blower unit; Sliding bearings; Fault; Lubrication; Scraping tiles; Find the center; preventive measures

1. Preface

The sliding bearing of the blast furnace blower unit is the transition between the rotating and stationary parts of the unit, and its service life directly affects the length of the unit maintenance cycle. If bearings cannot work safely, it will threaten the safe operation of the entire unit. If used properly, a pair of sliding bearings can operate continuously for more than three years, and some units have not replaced the bearings even after ten years of use. If used improperly, it is also possible to continuously damage several sets of bearings within a month, which has occurred in some units. The ideal situation for sliding bearings Z is to operate under liquid friction conditions, as the working surfaces of the shaft and bearing are separated by a lubricating oil layer, resulting in almost no wear on the working surfaces of the shaft and bearing. Therefore, the ideal working period for sliding bearings should be very long. However, due to the frequent need to start and stop the machine during operation, causing changes in speed, improper handling of some details during installation and maintenance, as well as vibration, load changes, and poor lubrication during operation, the machine will also experience damage to the liquid friction conditions and cause bearing wear, resulting in bearing failure. If we understand the causes of sliding bearing failures in blast furnace blower units and take corresponding preventive measures, it is entirely possible to eliminate bearing failures, extend bearing service life, and ensure safe and continuous operation of blast furnace blower units.

2. Analysis of the causes of sliding bearing faults in blast furnace blower units

The normal operation of sliding bearings depends not only on the quality of their manufacturing, installation, and maintenance, but also on changes in the working conditions of the unit and whether the oil supply equipment can supply oil well. Specifically, in terms of manufacturing, installation, and maintenance, it is important to pay attention to the casting quality of the black gold, which must be qualified. The black gold should not have defects such as detachment, cracks, sand heels, etc. There should be no iron filings or sand particles in the black gold; The installation clearance and tightening force of the bearings should meet the requirements, the bearing pads should be scraped correctly, and the center of the unit should be kept correct. The main things to pay attention to in operation are: monitoring the temperature of the bearing, the temperature of the lubricating oil, and whether the oil supply equipment is working properly, whether the vibration of the bearings is too large, and whether there are abnormal noises. The possible faults that may occur during the operation of sliding bearings are analyzed as follows:

(1) Insufficient or interrupted lubricating oil can cause an increase in bearing oil temperature, and in severe cases, it can lead to the melting of the black gold in the bearing shell. The main cause is: damage to the main oil pump (internal clearance changes, severe wear and tear); The transmission part that drives the main oil pump is damaged; Oil leakage or rupture in the inlet pipelines and connecting flanges of each bearing, and blockage in the oil pipelines; The oil level in the fuel tank is too low, causing the main oil pump to have insufficient oil suction or unable to suck up oil.

(2) The lubricating oil is not clean, and there are sand particles and impurities in the oil, which can be brought into the bearing and cause damage to the oil film. At this point, the temperature of the bearing and lubricating oil increases, which may even cause the black gold of the bearing to melt.

(3) Excessive vibration of the bearing can cause detachment and cracking of the black metal, damaging the oil film.

(4) The cooling water of the oil cooler is interrupted, and the oil temperature entering the bearing is too high. The viscosity of the oil decreases a lot, and the heat of the shaft neck cannot be taken away, so an oil film cannot be formed inside the bearing shell.

(5) Water in the lubricating oil causes damage to the oil film in the bearing. The main source of water in lubricating oil is steam leakage from the turbine shaft seal, excessive clearance between the shaft end seals, and steam leakage entering the bearings. If the pressure of the cooling water flowing through the oil cooler is greater than the oil pressure, the cooling water will leak into the oil when the heat exchange tube leaks.

(6) Due to excessive thermal deformation of the bearing housing during operation, the contact surface between the rotor journal and the bearing shell is subjected to uneven forces, resulting in the bearing shell not being able to fully contact the journal along the length direction, leading to wear and overheating of the bearing. This situation is more likely to occur on cylindrical bearing shells.

3. Preventive measures for sliding bearing failure of blast furnace blower unit

Based on the above analysis, the cause of the sliding bearing failure in the blast furnace blower unit may be due to manufacturing reasons, installation and maintenance reasons, or operational reasons. Generally speaking, manufacturing technology is very mature now, and strict quality control is implemented before leaving the factory. Manufacturing quality issues are rare. The failure of sliding bearings in blast furnace blower units is mainly caused by poor handling of some details in installation and maintenance, as well as improper operation. Therefore, preventing the failure of sliding bearings in blast furnace blower units mainly starts from two aspects: installation, maintenance, and operation.

3.1 Preventive measures for installation and maintenance

According to the actual situation, it has been found that improper scraping of the bearing shells and improper centering of the unit are the main reasons for bearing failures during the installation and maintenance of the blast furnace blower unit. Therefore, correctly scraping the bearing shells and correctly centering the unit are the key to preventing sliding bearing failures of the blast furnace blower.

3.1.1 Correct scraping of bearing shells

According to the working principle of high-speed sliding bearings, when repairing and scraping the bearing shell, the main task is to find a way to ensure the shape, size, and smoothness of the bearing shell. The correct shape for cylindrical bearings is a complete circle, and the diameter of the cylindrical bearing should be slightly larger than the diameter of the working shaft to ensure the formation of the correct wedge-shaped clearance. For elliptical bearings, the upper and lower halves are also circular with equal radii, but they are not concentric. The radius of the bearing shell is slightly larger than that of the working journal. The wedge-shaped shrinkage of elliptical bearings is slightly greater than that of cylindrical bearings. Whether for cylindrical bearings or elliptical bearings, the higher the requirement for the surface smoothness of the bearing shell, the better.

Hand scraped bearings require the use of a fake shaft (or measuring shaft), whose diameter is greater than the diameter of the working shaft neck, meaning that the diameter of the fake shaft is equal to the diameter of the working shaft plus the expected oil wedge clearance. When repairing and scraping the bearing shell, match it with the fake shaft. The scraped bearing shell should be circular, with a diameter difference between the bearing shell and the working journal, an expected wedge-shaped gap, and the working journal and the lower part of the bearing shell should be in line contact. Due to machining errors and deformations, the actual contact is a narrow surface, and this narrow surface along the axial direction should generally not exceed 10mm. Each half of the bearing shell scraped according to the fake shaft should be matched with the fake shaft. The higher the smoothness of the scraping process, the more favorable it is for the formation of an oil film. Especially in the lower part of the bearing shell at 60-70 °, which is usually the area where oil film is established to generate oil pressure, it must be very smooth. Within this range, it is not allowed to open oil holes, oil grooves, defects such as air holes and sand holes, and it is also not allowed to scrape pits to store oil. The drawing indicates that the contact angle of the bearing is 60-70 °, indicating that this range is the oil film pressure zone and must be taken very seriously. It does not mean that this range should be scraped to match the working journal. How to determine the size of the fake shaft? How much larger is its diameter than the working journal? This is determined based on the expected size of the wedge-shaped gap to be obtained. For cylindrical bearings, the diameter of the false shaft should be equal to the diameter of the working journal plus the top clearance.

3.1.2 Correctly locate the unit center

According to the actual situation, it was found that the method of finding the center of the unit was incorrect. The error in finding the center of the unit was too large, or it could be found in the cold state, but the center moved too much in the hot state, which would cause large vibration of the unit, severe bearing wear, loud noise, unstable operation, and also increase the load on the bearings, making it easy for bearing failures to occur. There are two main reasons for the large error in finding the center in the cold state: ① Not careful enough; ② The central tool system itself has a large error. To find the unit center correctly, the following points should be mainly achieved:

(1) Confirm whether the tool system of the search center is reliable. Attach the dial gauge to your own axis and check if there is a change in the reading when the dial gauge is slightly above Z and rotated 180 ° with the axis when the surface is upward. This can help determine if there is a problem with the centering tool system.

(2) When searching for the center, both axes should be marked with positioning marks and rotated simultaneously to eliminate machining errors in the parts.

(3) When searching for the center, Z should look for the top, bottom, left, and right points. The sum of two numbers on any diameter of the outer circle should be a constant. Therefore, when verifying data, regardless of the actual deviation of the center, the sum of the upper and lower numbers and the sum of the left and right numbers should be equal; When finding the end face opening, if the axial positions of the two shafts can be relatively fixed, then the data of the end face opening should also be equal to the sum of the upper and lower numbers and the left and right numbers, regardless of the actual size of the opening.

(4) You should search for the center three times in a row. You can search clockwise once, counterclockwise once, and move the center finding tool 180 ° relative to each other again. The results of several center finding attempts should be the same.

(5) When searching for the center, consideration should be given to the thermal deformation of the unit based on its design parameters, and pre compensation should be carried out when searching for the center in the cold state.

3.2 Preventive measures for operational aspects

(1) Continuously monitor the working condition of oil supply equipment (main oil pump, auxiliary oil pump, oil cooler, pressure reducing valve, overflow valve, oil tank, oil injector, etc.) during operation to ensure normal operation. The working condition of these devices is mainly judged based on the inlet oil pressure and oil temperature. If any abnormalities are found, corresponding measures should be taken immediately.

(2) Continuously monitor the bearing temperature, and if any changes are found in the bearing temperature, the cause must be identified and eliminated. The temperature of the thrust bearing should be given more attention. Even a slight increase in temperature may indicate severe wear of the Uyghur metal. Sometimes, even if the temperature of the thrust bearing only rises by 1-2 ℃, the Uyghur metal has already worn out a lot. If the temperature rises by 8-15 ℃, not only has the Uyghur metal melted, but the thrust tile itself has also been severely worn.

(3) Regularly observe the vibration values of the bearings and the axial displacement of the rotor, and pay attention to the pressure changes in each monitoring section of the turbine. If any abnormalities are found, they should be analyzed immediately to identify the cause and dealt with decisively.

(4) Strictly monitor the operating conditions of the blower and never allow it to operate under unstable conditions.

The blast furnace blower unit is one of the key equipment in the blast furnace smelting system. If an accident occurs, the direct and indirect losses caused will be enormous. By taking corresponding preventive measures, the failure of sliding bearings can be avoided. With proper installation, maintenance, and operation, sliding bearings can operate safely and stably for a long time.

2025 November 3rd Week Marginal Product Recommendation:

Three-layer metal-polymer self-lubricating bearings:

Three-layer metal-polymer self-lubricating bearing is lighter and has better mechanical and load performance. In addition, the wear resistance and noise absorbing feature is improved while more variable torque range could be fitted.

https://www.marginalbearings.com/bimetallic-bushes/three-layer-metal-polymer-self-lubricating.html