Lubrication

Of

Roller Bearings

Roller Bearings have a long history

around 700 BC

1794

186940 AC

around3000 BC

Tasks of Roller Bearings

reducing friction

transfer of loads

guiding rotating parts

Friction

Energy losses through friction

µ – 10 % = 1/2 E [AUS+BR+E+S]

„Although rolling friction is already very low, manufacturers of roller bearings and lubricants work continuously on further improvements..“

SKF— one of the world´s biggest manufacturers of roller

bearingsmade the following calculation:

If it can be managed to drop the friction in all roller bearingsinstalled on the globe only by further 10%,

the combined total electricity consumption of the countriesAustralia, Brasil, Spain und Sweden

could be cut to a half !

Roller Bearings are named after the Shape of their rolling Elements

ball spherical rollersymmetrical

spherical rollerasymmetrical

cylindrical roller

needle roller

conical roller

Friction in Roller Bearings

small portion of rolling friction

but considerable share of sliding friction at:

roller bearing ringscages and / orrolling elements against each other

Kinds of Lubricationof Roller Bearings

9,5% by oils 0,5% by solid lubricants only

90% by greases

The most important Parameters for selecting the suitable Lubricant

revolution or DN - factor

D = external bearing diameter [mm]d = internal bearing diameter [mm]n = revolution per minute [rpm]dm= medium bearing diameter [mm] = ———D + d

2

DN = ——— • nD + d2

temperature range

DN- Factors for OKS Bearing Greases

Temperature Range of OKS Bearing Greases

with MoS2

with MoS2 + Mox - Active

with MoS2 with Mox - Active

with MoS2 + Mox - Activewith PTFE

with PTFE

with white solid lubricants

with PTFE

Lubrication by greases

Grease pump

Contamination maycause bearing failures.Seals protect to a largeextent from outside contaminations. Frequent relubrication is required when

the hazard of grease contamination exists.Same applies if the grease should seal alsoagainst penetrating moisture.

Contamination penetrating throughlabyrinth channels.

Newly supplied grease pushes out bothused up and contaminated grease through the labyrinth packing seals.

Relubrication Intervals for Grease lubricated Roller Bearings

Small bearings with lateral seals or cover plates do not need any relubrication. They are already for - life lubricated.

For all other roller bearings relubrication intervals become valid.

Guidelines forRelubrication Intervalls

10 000

6 000

4 000

3 000

2 000

1 500

1 000

500

300

200

150

100

50

20 000

15 000

10 000

7 500

5 000

2 500

1 500

1 000

750

500

250

20 000

15 000

10 000

5 000

3 000

2 000

1 500

1 000

500

100 200 500 1 000 2 000 5 000 10 000n [U/min]

tfa

tfb

tfcLubrication interval,given by service hours

tfa = radial ball bearingtfb = cylindrical roller bearing / needle bearingtfc = self aligning roller bearing / taper rolling bearing / axial roller bearing massive cylindrical roller bearing (0,2 tfc), axial cylindrical roller bearing (0,5 tfc)

500 420 360 280 240 200 160 120 100 80 6040

20

d=10

Example: A deep-groove ball bearing with an internal diameter d= 100mm running at a speed of n = 1000 rpm. The operating temperature lies between 60 and 70 °C.Which is the expected relubrication interval?

The vertical in point n= 1000 rpm on the abscissacuts the curve for d= 100mm. From there the horizontal leads to the outer left-hand scale (deep- groove ball bearings)indicating a relubrication interval of 10000 service hours

Correction of Relubrication Intervals

The assessed intervals are valid only for:

bearings in stationary machines

normal load

ageing-proofed greases

temperature < + 70°C at the outer ring

Dependance of Relubrication Intervals on Tempearture

100

85

70

55

40

Lubrication interval°C

Temperature at the outer ring

above 70°C the factor 0,5 appliesfor each temperature rise of 15°C

i.e. with a temperature rise from e.g.70°C up to 85°C the service life ofthe grease is cut by half.

below 70°C the factor 2 appliesfor each temperature drop of 15°C

i.e. with a temperature drop from e.g.70°C down to 55 °C the service life of the grease is doubled.

Lubrication by Oil

is used at high speeds resp. at DN-factors exceeding1.000.000 and in case heat conduction is necessary.

Oil bath lubrication

Suitable only for bearings with low speeds.During stand-stills the oil level should notquite reach the middle of the rolling elementat the bottom. .

Oil injection lubrication

At high speed it becomes necessary, that the air turbulence circulating withthe bearing is penetrated by the oil.This is ensured by injecting oil underhigh pressure (min.15 m/s) from the sideinto the bearing.

Circulatory oil lubrication

With increasing speed the service temperaturerises and accelerates the ageing of thelubricating oil.By circulatory lubrication the oil can be cooled and consequentlythe service temperature be reduced.

Cooling

pump

Lubrication with Solid Lubricants

Deep groove ball bearings with increased clearance required at:

high temperatures > + 200 °C

high temperature variations

low speed

Lubrication with Solid Lubricants - Exsample

Lubrication by Solid Lubricants only

at temperatures > + 200 °C

OKS 230 MoS2-High Temperature Paste(for thin-film lubrication during assembly and maintenance)

in connection with

OKS 310 MoS2-High-Temperature Lubricant(for relubrication during operation)

The carrying fluid evaporates residue-free above 200°C and dry MoS2 films remain, which assure lubrication up to 450°C.

Kiln-car bearings in the ceramics and brick industry

OKS Speciality Lubricants forRoller Bearings at:

High loads

Shock stress

Vibrations

Low or high speed

Stop-and-go operation

Very low or very high temperatures

Temperature variations

Humid conditions

Corrosive influences

Long-term lubricating needs

Use in the food industry

Thank You

for Your

Attention