Abstract: Through analysis of damage to sliding bearings, the preventive measures that should be taken in actual work are described.

Keywords: machinery; bearing; sliding bearing; bearing damage

Bearings are an important factor affecting the service life of the entire machine. Although sliding bearings are not as widely used in general machinery as rolling bearings, their unique advantages mean that they still occupy an important position in applications involving high speed, high precision, heavy load, and restricted radial dimensions.

In actual work, due to various reasons, sliding bearings cannot reach their expected service life and suffer premature damage. Based on many years of management experience, the author analyzes the causes of sliding bearing damage and proposes corresponding preventive measures.

1 Analysis of Sliding Bearing Damage

1.1 Scuffing

Scuffing is the melting and transfer of the anti-friction layer material of the bearing. If oil is lacking, the metal surfaces of the bearing and journal will come into direct contact, causing scratches on the working surface and resulting in scuffing. If lubricating oil is not added, the residual oil may be completely squeezed out. Dry friction between the shaft and bearing causes a sharp rise in temperature; the bearing material softens, melts, and undergoes adhesive transfer, causing severe damage to the shaft and bearing. The main causes of scuffing are excessive overload operation, localized load concentration, poor or blocked oil passages, failure of the filter to perform its proper function, and difficulty in forming oil film conditions (such as excessively high oil temperature, excessively large fit clearance, and diluted oil). In addition, if the lubricating oil is unclean, dirt or metal chips in the oil can easily become embedded in the anti-friction layer to form hard particles. When their height is greater than the bearing clearance, they will also grind grooves in the working surface.

1.2 Wear

Wear is an unavoidable type of damage during operation of sliding bearings; here the emphasis is on early wear and excessive wear. The most common wear failures are still adhesive wear and abrasive wear. Adhesive wear occurs under boundary lubrication conditions when the oil film breaks down or foreign matter becomes embedded in the bearing metal surface, causing direct local contact between the metal surfaces of the shaft and bearing. Frictional heating raises the oil temperature and reduces viscosity. Sometimes the heating causes the surface metal to flow and produce adhesion, and in severe cases the machine is instantly unable to operate. If momentary dry friction occurs between the shaft and bearing, or impurities in the lubricating oil enter between the shaft and bearing, abrasive wear often occurs. With poor lubrication and ineffective filtration of wear debris, sliding bearing wear intensifies, affecting normal operation and causing premature failure.

1.3 Fatigue

Sliding bearings often operate under alternating loads. If the stress exceeds the fatigue strength of the material, after a certain number of stress cycles, cracks will form on the bearing surface, and the cracks will propagate from the surface toward the interior along the direction of maximum stress. In addition, rupture of the oil film causes seizure of the bearing, and the resulting scars can also become new fatigue sources. Generally, fatigue cracks propagate inward from the surface to near the bonding interface, and then propagate along the bonding interface. When these cracks meet each other along the bonding interface, they cause detachment of the bearing alloy material and plating. Irregular small spots and spalling appear on the bearing surface, i.e., fatigue damage occurs, ultimately leading to bearing failure.

1.4 Corrosion

Bearings using uncoated copper-lead alloy or lead-based white metal often undergo corrosion. This is because a small amount of water or acid remains in the lubricating oil, or other factors (such as acidic substances generated by the machine during operation) cause oxidation after long-term high-temperature operation, generating organic acids that corrode the bearing alloy, producing pits and corrosion lesions, reducing the bearing support area and hindering oil film formation.

1.5 Bushing Burning

Long-term lack of lubrication of the bearing, excessively large or small assembly clearance, locally excessive or insufficient clearance, overload operation, and the presence of impurities and foreign matter between bearings make it difficult to form a pressure oil film between the bearings and destroy the load-carrying capacity of the oil film. All of these will cause the bearing to “overheat,” causing softening of the bushing material and even local melting, bonding the shaft and bearing together, resulting in “shaft seizure,” leading to burning of the shaft and bushing. This is the most serious type of damage and often immediately causes an accident.

2 Preventive Measures

2.1 Preparatory Work Before Operation

2.1.1 Reasonably Select Lubricant and Ensure Its Quality

Whenever two interacting surfaces move relative to each other, friction and wear occur. To reduce friction and wear, correct and reasonable selection of lubricant must be considered. It is a prerequisite for ensuring good lubrication and also a necessary condition for preventing abnormal wear. If the lubricant is improperly selected, it cannot form an oil film of sufficient thickness between the friction pair. Under relative motion and load, plastic deformation will occur at the contact areas of the friction pair, the temperature of the friction surfaces will rise, and the oil film will rupture. As the temperature continues to rise, the surface structure of the sliding bearing softens or melts, at which point tearing, adhesion, seizure, and similar phenomena occur.

For lubricating oil, viscosity and quality are two aspects to consider when selecting. Proper selection of viscosity can not only form liquid lubrication and reduce wear, but also achieve maximum energy-saving effect. Lubricating oil quality is also a key factor. Only on the basis of ensuring oil quality can other measures play their role. Therefore, a “three-stage” filtration system must be strictly implemented for lubricating oil. If the lubricating oil oxidizes and contains dust, poor lubrication will result.

Practice has proven that the selection of lubricant should consider factors such as the form and speed of motion of the friction pair, the load magnitude on the friction pair, external conditions, and operating temperature.

2.1.2 Correct Selection of Bearing Clearance

The size of the clearances in various parts of a sliding bearing has a great influence on its operation, lubrication, and wear. Excessively large axial clearance will result in poor axial stability of the journal and easy oil leakage; excessively small axial clearance will prevent compensation for axial thermal expansion of the shaft, causing the end of the bushing to heat up and preventing normal operation. Excessively large radial clearance will cause oil leakage and vibration, reduce oil wedge pressure, make lubrication difficult, and accelerate wear; excessively small radial clearance will also reduce oil wedge size, make heat dissipation difficult, and reduce oil supply, causing the bearing to heat up.

The selection of clearance involves many factors, such as the running-in performance of the bushing material, elastic deformation, coefficient of linear expansion, relative sliding speed, lubricating material and method, cleanliness standard, journal material, surface roughness, deformation amount, and coaxiality. The clearance should be selected according to the specific conditions of the above parameters.

2.1.3 Ensure Assembly Quality

The installation and technical dimensional requirements of the sliding bearing and bushing surface must be ensured; lubricating oil passages must be kept unobstructed, sealing must be strict; and the technical condition of each assembled part must be qualified. Only in this way can the bearing operate in a good environment and avoid failure.

In addition, before installation, each component must be thoroughly cleaned and washed in strict accordance with the cleaning process, and must be inspected strictly according to cleanliness standards. According to relevant literature, the United States, Japan, and the United Kingdom once analyzed bushing burning accidents of automotive engine sliding bearings, and the proportion of bushing burning caused by impurities and foreign matter all exceeded 30%. Professor Franz of the well-known Austrian Miba Sliding Bearing Company asserted based on their practice: “80% of bushing failures are caused by contaminants.”

2.2 Strengthen Maintenance and Care During Operation

2.2.1 Bearings Must Be Cleaned Regularly

Oil contamination and abrasive particles in the friction pair of sliding bearings must be cleaned regularly; otherwise, over time, accumulated impurities and abrasive particles will cause disaster. At the same time, oxides produced after long-term use of the lubricant cause the lubricant to deteriorate and lose effectiveness, resulting in early wear and scuffing of the bearing. Therefore, timely cleaning and treatment should be carried out, and protective devices should be installed to prevent the ingress of external contaminants such as dust, water, and abrasive particles.

2.2.2 Replace Lubricating Oil in a Timely Manner

Determining the oil change interval is a very important and complex issue. It is generally determined according to factors such as the operating environment, working conditions, and maintenance and repair. Lubricating oil deteriorates and forms deposits during use. The main basis for replacement is analysis and testing of the viscosity, pH value, water content, and amount of insolubles in the lubricating oil.

2.2.3 Ensure the Supply of Lubricant

The main purpose of lubrication is to reduce machine wear, minimize the friction coefficient, improve the overall efficiency of equipment, and extend equipment service life. If lubricant is lacking, wear and other corresponding damage are difficult to avoid. At the same time, under normal conditions, the lubricant between the friction pair also makes it difficult for impurities to enter.

If lubricating oil is used, ensuring supply means not only adding a sufficient amount of lubricating oil, but also supplying a sufficient amount of lubricating oil to the lubrication system. In addition, the oil station should be inspected, maintained, and cleaned regularly.

2.3 Other Aspects

Strengthen daily maintenance and inspection, improve the technical level and sense of responsibility of operators and maintenance personnel, and resolutely prevent leakage, spillage, dripping, and seepage in oil lines as well as long-term overload operation of mechanical equipment. Once bearing abnormalities are found, they should be handled promptly to prevent the situation from expanding and ensure normal, safe, and sound operation of the equipment. In addition, strengthen technical management during use and maintenance to avoid early wear of sliding bearings, thereby extending the service life of sliding bearings and the entire machine.

2026 October 2nd Week Marginal Product Recommendation

MG-090 Bronze Wrapped Bushings:
MG-090 bronze self-lubricating bearings use a kind of high density bronze alloy of special compositions as backing, the surface of alloy is rolled with diamond pattern of the oil indents or half ball oil indents, this kind of bearing has a higher density, a higher load capacity.

https://www.marginalbearings.com/bronze-wrapped-bushings/mg-090-bronze-wrapped-bushing.html