Lubrication Of Plain Bearings

1. Lubrication Of Plain Bearings

2. Plain Bearings are theoldest 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.)

3. Plain Bearings in modern machines Plain bearings are indispensable in nowadays technology. A car engine contains more than 90 % plain bearings.

4. Friction in Plain Bearings Stribeck-Kurve Stribeck Diagram friction valueµ number of revolutions/sliding speed mixed friction boundary friction hydrodynamic friction l rest position of the shaft, metal / metal contact (no lubrication between shaft and bearing) 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)

5. 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.

6. Comparison of Plainand Roller Bearings

7. Determining Factorsfor Plain Bearings p = bearing load v = sliding speed p x v – value D d B D

8. Determining Factorsfor Plain Bearings [ ] N mm² bearing load: F D x B pm = ——— pm = average surface pressure [N/mm2] F= active force [N] D = diameter of bearing [mm] B = width of bearing [mm] • . D xx n 100 x 60 v = ——— sliding speed: [ ] m S v = sliding speed [m/s] D = diameter of bearing [mm] n = number of revolutions [rpm]

9. Guide for Plain Bearing materials

10. Selection Guide for Lubricants high viscosity l low sliding speed low viscosity l high sliding speed high viscosity l high bearing clearance higher viscosity l high load (bearing pressure) 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 con- sideration of the type of lubricant supply.

11. 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

12. Permanent oil circulation withsimultaneous 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.

13. Interval Lubrication Lubrication in determined time intervals with oil or grease

14. For-life Lubrication(maintenance free) l sintered bearings (oil-impregnated) l lubricant depot (lubricant grooves/lubricant pockets)

15. Self Lubrication Plain bearing materials based on thermo-plastics with additives like MoS2

16. OKS Speciality Lubricantsfor Plain Bearings with: 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 primary requirements

17. OKS Speciality Lubricantsfor Plain Bearings with: regulations of the food industry compatibility with plastics secondary requirements

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