Lubrication Of Plain Bearings Plain Bearings are the
Lubrication Of Plain Bearings
Plain Bearings are the oldest Types of Bearings l At first shafts and bushes were made of wood. Later iron and bronze were used. l The lubrication was done with olive oil or with a mixture of oil and lime. Roman building crane with pulley block and human power drive. (500 B. C. )
Plain Bearings in modern machines Plain bearings are indispensable in nowadays technology. A car engine contains more than 90 % plain bearings.
friction value µ Friction in Plain Bearings Stribeck-Kurve Stribeck Diagram l rest position of the shaft, metal / metal contact (no lubrication between shaft and bearing) number of revolutions/sliding speed l with increasing speed an oil film between bearing and shaft is developed. l it finally results in a total separation of shaft and bush. (The friction increases with higher speed (rpm) in this sector of hydrodynamic friction) boundary friction mixed friction hydrodynamic friction
Plain Bearing If possible, the bushes, made out of a material with good sliding abilities, will be put into a housing of cast iron with good mechanical stability. The bushes remain replaceable.
Comparison of Plain and Roller Bearings
Determining Factors for Plain Bearings p x v – value d p = bearing load v = sliding speed D D B
Determining Factors for Plain Bearings bearing load: F pm = ——— Dx. B N [ mm² ] pm = average surface pressure [N/mm 2] F = active force [N] D = diameter of bearing [mm] B = width of bearing [mm] sliding speed: D x πx. n v = ——— 100 x 60 [ m S ] v = sliding speed [m/s] D = diameter of bearing [mm] n = number of revolutions [rpm]
Guide for Plain Bearing materials
Selection Guide for Lubricants The viscosity of a lubricating oil — in a grease the base oil viscosity — is decisively for the right thickness of the lubricating film (approx. 3 -30µm) under consideration of the type of lubricant supply. l low sliding speed high viscosity l high sliding speed low viscosity l high bearing clearance high viscosity l high load (bearing pressure) higher viscosity
Lubricant supply Depending on the demands, very different ways of Lubrication may be used l permanent oil–circulation lubrication l interval lubrication l for-life lubrication l self-lubrication
Permanent oil circulation with simultaneous heat dissipation l car engines l steam and water turbines Standard is an oil pressure between 0, 5 and 5 bar. If higher pressure is used it is called forced-oil lubrication.
Interval Lubrication in determined time intervals with oil or grease
For-life Lubrication (maintenance free) l sintered bearings (oil-impregnated) l lubricant depot (lubricant grooves/lubricant pockets)
Self Lubrication Plain bearing materials based on thermo-plastics with additives like Mo. S 2
OKS Speciality Lubricants for Plain Bearings with: primary requirements high loads impact loads vibrations low or high number of revolutions Stop-and-go operations deepest temperatures highest temperatures variation in temperature influence of moisture corrosive influence demand for long life lubrication
OKS Speciality Lubricants for Plain Bearings with: secondary requirements regulations of the food industry compatibility with plastics
Thank You for Your Attention
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