[Abstract] Explores various factors that affect the lubricating oil film of low-speed and heavy-duty sliding bearings, studies and analyzes the main lubrication problems in domestic engineering operations, analyzes and discusses the factors that cause poor lubrication, and proposes effective solutions.
[Keywords] Low speed heavy load; Sliding bearings; Lubricating oil film; Causing factors; Fault handling
In modern enterprise production, low-speed and heavy-duty equipment is widely used. In order to ensure the normal use of equipment, sliding bearings are usually used to effectively protect the equipment. In use, there are certain requirements for the speed and average load pressure of the bearings. Sliding bearings are mainly used to reduce friction between instruments and increase their service life. They are stable and have low noise during operation. The use of lubricating oil film in bearings can effectively reduce surface wear of bearings and equipment wear losses caused by friction, affecting the service life of equipment. In practical operation, due to the uneven distribution of oil film and ineffective formation of oil film in the use of lubricating oil, many problems occur in the operation of bearings, seriously affecting the use of low-speed and heavy-duty sliding bearings. Therefore, analyzing the factors that affect the oil film and proposing solutions plays an important role.
1. Factors affecting lubricating oil film
1.1 Water cooling of bearing shells
Excessive bearing temperature can cause damage to the bearing and affect its normal operation. The cooling of bearing shell temperature is the key point of bearing cooling work. In testing, the temperature of the bearing shell is generally used as the temperature of the bearing. When the temperature of the bearing shell is too high, lubricating oil cannot enter the gap between the bearing shell and the journal normally, and the oil film cannot effectively form lubrication between the two, ultimately leading to damage to the bearing shell. In the design of low-speed and heavy-duty sliding bearings, water flow is generally used to cool the bearing shells. The cooling water channel must be tightly attached to the back of the bearing shells and installed on the bearing seat. When constructing the size of the bearing, by designing the cooling water channel reasonably and increasing the channel area, the cooling degree of the bearing is significantly improved, and the working efficiency of the bearing is also significantly improved, while ensuring the normal operation of the bearing.
1.2 Problems with Bearing Material
In the selection of bearing material for low-speed and heavy-duty equipment, Babbitt alloy is usually used as the raw material. This alloy has a large size and certain quality problems, which has a serious impact on the lubrication of bearings, ultimately leading to bearing failure and affecting the working and service life of bearings. A prominent issue in the selection of bearing pad materials is the pouring of the bearing pad lining layer, which mainly focuses on several issues: (1) improper treatment between the lining layer and the backing layer leads to ineffective bonding, ultimately leading to poor lubrication of the bearing, ineffective formation of lubricating oil film, and ultimately causing the bearing to not work properly. (2) The cooling rate of Babbitt alloy during operation weakens, causing the fracture of tin antimony grains and mixing into the lubricating oil, Causing severe wear on bearings. (3) If there is a deviation in the temperature control of the bearing bush during pouring, it will also have a certain impact on the working performance of the bearing.
1.3 Effect of oil film thickness on bearing lubricating oil film
Bearings of different sizes have different speeds during operation, and the bearing capacity of the oil layer also varies. Low speed operation leads to a corresponding reduction in the bearing capacity of the oil layer, resulting in lower requirements for lubricating oil. However, for large equipment such as aluminum hot rolling mills that operate at low speeds but with heavy loads, the lubricating oil layer needs to withstand enormous pressure during operation. In order to ensure better bearing operation and the required load force, in the use of lubricating oil, the bearing spacing should be reduced to increase the viscosity of the lubricating oil, Reasonably design the oil groove to ensure that the lubricating oil can evenly and fully distribute the contact surfaces between various parts of the bearing when entering. During the operation of sliding bearings, there is a close relationship between the oil film thickness and the oil wedge. The minimum oil film thickness is proportional to the bearing spacing and inversely proportional to the bearing capacity coefficient required for operation, provided it meets the usage standards. In practical use, there may be slight unevenness between the bearing shells and shafts. Therefore, before use, necessary maintenance should be carried out on the journal, bearings, and shafts to ensure normal operation before putting them into use. In order to ensure that the oil film can effectively cover the micro unevenness between the bearing equipment during bearing operation, it is necessary to control the minimum thickness of the oil film. When designing sliding bearings, the initial operating clearance should not be too small, as the installation cost of the bearings is closely related to the machining accuracy of the bearing equipment. The higher the machining accuracy, the higher the required cost. Therefore, it is necessary to design the bearing clearance reasonably to ensure that the use needs are met while taking into account economic benefits, and to ensure that the minimum oil film thickness of the bearings can be formed between equipment. However, the bearing clearance must be moderate, Avoid damage to bearings caused by high temperatures generated by friction during use.
2. Troubleshooting of lubricating oil film faults
(1) When inspecting and treating the lubricating oil film, the above methods mainly include effective supervision of the operating parameters and lubricating oil of the bearing shells. Conduct regular maintenance on the equipment, inspect the distribution of oil film, contact area of oil film, and the distribution of oil film defects. When the contact angle between the shaft and journal is 80-900, it indicates that the distribution of the oil film is good and the film formation is relatively low. The problem of large area oil film drying and uneven oil distribution on the bearing pad can lead to poor oil film operation. Therefore, redesign the size and structure of the oil groove, increase the viscosity of the oil film, or improve the bearing pad by scraping and grinding. Real time monitoring of the temperature of the bearing is necessary. During the running in stage of the bearing, the temperature of the bearing must be guaranteed to be between 45-60C. If the bearing temperature exceeds this range, it indicates that the cooling water or lubrication condition of the bearing is poor and needs improvement. The clearance of bearings is closely related to the lubricating oil film of bearings, with the spacing between the journal and the bearing pad being the most important. After a period of bearing operation, the degree of wear at both ends of the bearing may vary, leading to abnormalities in the bearing. At this time, it is necessary to closely inspect the glands between the bearings and solve the problem in a timely manner.
(2) The oil bath design must meet the formation needs of oil film lubrication. The lubricating oil used in low-speed heavy load bearings is not in a completely liquid state and has a high viscosity. Therefore, the requirements for the oil bath are high. The oil bath design must ensure that the lubricating oil can be fully introduced and evenly distributed. The uniform distribution of lubricating oil film helps to reduce the energy consumption generated by bearing friction, while effectively evaporating the heat generated during friction to the maximum extent possible. Therefore, ensuring uniform distribution of lubricating oil in the production of oil film lubrication has become the main content of oil groove design. The reasonable layout of the oil tank must be accompanied by a scientific design of the size and structure of the oil film. The oil injection hole cannot enter the bearing's friction interface from the load-bearing area. In order to effectively improve the formation of oil film, an annular oil groove can be used, but the position of the oil groove should be fully considered during design. When the distribution of lubricating oil is uneven, there will be dry wear inside the bearing pads, and there is indeed a more serious phenomenon in the center of the shaft. To reduce this phenomenon, it is necessary to avoid excessively sharp edges of the oil groove when designing it.
(3) The flow rate of cooling water has an important relationship with the temperature changes of bearings, so reasonable modification of cooling water can effectively improve the phenomenon of excessive bearing temperature. Mainly by expanding the length and area of cooling water, promoting the flow of cooling water and effectively improving the phenomenon of high bearing temperature.
(4) When improving the babbitt alloy, it is necessary to strictly control the temperature of the bearing pad backing and lining layer, and apply solder or pure tin on the heated bearing pad. At the same time, the temperature and speed of alloy pouring should be reasonably controlled during pouring.
In the production of modern enterprises, large-scale production has become the main feature. The reasonable use of machinery can effectively improve production efficiency, prolong the service life of equipment, and reduce the costs caused by mechanical maintenance or replacement. The lubricating oil film of low-speed heavy load sliding bearing can effectively reduce the friction in the operation of equipment and the loss of machinery. However, there are still serious problems in the use of lubricating oil layer. The management and maintenance personnel can take effective measures to reduce the occurrence of faults in use when designing, which is of great significance for improving the economic benefits of enterprises.
More about Epen EMT Bushings:
EMT bi-metallic bushing is formed from steel strips with alloy lining material. The alloy lined surface can be machined oil grooves, holes, formed Indentations etc according to different application. It is suitable for high load, lower speed oscillation & rotation movement.