”The Art” of chosing the right grease lies mainly in proper ranking of the properties required from the base fluid, thickener and additives as a result of the critical operating conditions.

1. INTRODUCTION TO GREASES
Prepared By
Md Aminul Islam

2. GREASE SELECTION TECHNIQUES

3. ”The Art” of chosing the right grease lies mainly in proper ranking of the properties
required from the base fluid, thickener and additives as a result of the critical operating
conditions.
LIFE
EXPECTANCY
TEMPERATURE
LOAD & SPEED
ENVIRONMENT
GREASING
METHOD
Critical operating conditions can f.ex. be;
1. High, Low or varying operating temperature
2. Shock and impacting loads
3. Water washout, flushing or other wet housing
4. Severely vibrating housing
5. Low starting temperature
6. Under-sized or inadequate central system
7. High centripetal acceleration
8. Long re-lubrication or exchange intervals
9. Agressive environment - chemicals, radiation, dust etc.
10. High, Low or wide speed range
11. High, Low or great variation in axial and radial load
Greases – Selection techniques

4. Choosing the best lubricant for an application is driven by several equipment considerations.
1. OEM recommendation
2. Operating speed
3. Operating temperature
4. Operating load
5. Shock load
6. Operating environment (heat, dust, water, chemicals, others)
Greases – Selection techniques

5. Greases – Selection techniques - OEM recommendation
Particularly for OEM equipment that is still under the warranty period, never recommend a
lubricant that does not meet the OEM recommendation. If you do, you may assume
financial liability for the machine, should it fail due to your recommendation. . . .
If and when a piece of equipment is not performing to levels expected by the OEM or the
customer, consult with the OEM to determine if you may improve perfromance through
lubrication. If successful, you may result in a change to the OEM specification & listing of
Shell products in the approval list
Sometimes the OEM will not recommend products, but require Shell to meet their
standards. This transfers the liability to the lubricant vendor
Be aware of OEM standards when rationlising products from many to fewer, ensure you do
not compromise an application for the sake of convenience.

6. Greases – Selection techniques - operating speed
Operating speed is the single most important factor in choosing a grease. It will determine
the viscosity required.
There are “standard methods” of determining viscosity, from very basic, using DN value of a
bearing, to very sophisticated, using a23 bearing life.
We will discuss several methods that will allow you to chose the right viscosity for operating
conditions.

7. Greases Selection techniques - operating speed/viscosity
DN Value - for friction bearings (bushes, plain bearings, journal bearings)
Dynamic Number value is determined by multiplying the average bearing circumference (in
mm) by the revolutions per minute of the bearing. This number is the DN value, sometimes
also referred to as “speed factor”.
Remember that for bushings (friction bearings), the diameter is the inside diameter of the
bearing or the outside diameter of the shaft.
So for a shaft size of 175 mm (0.55 metres) x revolutions per minute (500 RPM) = surface
speed of 275 metres per minute, the DN value is 275
Once DN value is determined, we refer to standard charts for lubricating bearings & select
the viscosity range (according to temperature of the bearing).

8. Now refer to chart. In
this example we have a
plain bearing with a
shaft diameter of 175
mm rotating at 500
RPM. The DN Value or
speed factor is 275
You can recalculate on
this slide by double
clicking the embedded
excel sheet & entering
new RPM
Greases Selection techniques - operating speed/viscosity
Shaft diameter
(mm)
Shaft diameter
(metres)
Shaft
circumfrence
(metres)
RPM DN (speed
factor)
75 0.08 0.24 500 118
100 0.10 0.31 500 157
125 0.13 0.39 500 196
150 0.15 0.47 500 236
175 0.18 0.55 500 275
200 0.20 0.63 500 314
225 0.23 0.71 500 353
250 0.25 0.79 500 393
275 0.28 0.86 500 432
300 0.30 0.94 500 471
325 0.33 1.02 500 510
350 0.35 1.10 500 550
375 0.38 1.18 500 589
400 0.40 1.26 500 628
425 0.43 1.33 500 667
450 0.45 1.41 500 707
475 0.48 1.49 500 746
500 0.50 1.57 500 785

9. Now compare DN value to operating temperature on the chart. In this example we have a
plain bearing with a DN Value or speed factor is 275 @ operating temperature between 50
oC and 65 oC, so the viscosity requirement is ISO 100.
You can recalculate on this slide by double clicking the embedded excel sheet & entering
new temperature
Greases Selection techniques - operating speed/viscosity
Plain Journal bearings Plain Journal bearings
Shaft surface speed 0 o
C - 30 o
C 30 o
C- 60 o
C > 60 o
C Shaft surface speed
= Shaft circumference
(meter) X RPM
R&O ISO Grade R&O ISO Grade R&O ISO Grade
= Shaft circumference
(meter) X RPM
< 60 68 220 1,000 < 60
60 - 150 46 150 460 60 - 150
150 - 300 32 - 46 100 220 150 - 300
300 - 760 22 46 - 68 150 - 220 300 - 760
> 760 10 46 150 > 760
= Shaft circumference
(meter) X RPM
R&O ISO Grade R&O ISO Grade R&O ISO Grade
= Shaft circumference
(meter) X RPM
Shaft surface speed 0 o
C - 30 o
C 30 o
C- 60 o
C > 60 o
C Shaft surface speed
Plain Journal bearings Plain Journal bearings
Approximate operating temperature range
Approximate operating temperature range
DNValue(Speedfactor)
DNValue(Speedfactor)

10. Greases Selection techniques - operating speed/viscosity
DN Value - for anti friction bearings
Dynamic Number value is determined by multiplying the average bearing diameter (in mm)
by the revolutions per minute of the bearing. This number is the DN value, sometimes also
referred to as “speed factor”.
Remember that for bushings (friction bearings), the diameter is the inside diameter of the
bearing or the outside diameter of the shaft.
So for a shaft size of 100 mm x 1,000 RPM, the DN value is 100*1,000 = 100,000
Once DN value is determined, we refer to standard charts for lubricating bearings & select
the viscosity range (according to temperature of the bearing). For example the bearing is
operating at between 80 oC and 90 oC.

11. Look up the DN value for the bearing you are considering on the chart below.
You can refer to all by double clicking the embedded excel sheet. Note that fields marked in gold are beyond the
Greases Selection techniques - operating speed/viscosity
50 100 150 200 250 500 750
25 1,250 2,500 3,750 5,000 6,250 12,500 18,750
50 2,500 5,000 7,500 10,000 12,500 25,000 37,500
75 3,750 7,500 11,250 15,000 18,750 37,500 56,250
100 5,000 10,000 15,000 20,000 25,000 50,000 75,000
125 6,250 12,500 18,750 25,000 31,250 62,500 93,750
150 7,500 15,000 22,500 30,000 37,500 75,000 112,500
175 8,750 17,500 26,250 35,000 43,750 87,500 131,250
200 10,000 20,000 30,000 40,000 50,000 100,000 150,000
225 11,250 22,500 33,750 45,000 56,250 112,500 168,750
250 12,500 25,000 37,500 50,000 62,500 125,000 187,500
275 13,750 27,500 41,250 55,000 68,750 137,500 206,250
300 15,000 30,000 45,000 60,000 75,000 150,000 225,000
325 16,250 32,500 48,750 65,000 81,250 162,500 243,750
350 17,500 35,000 52,500 70,000 87,500 175,000 262,500
375 18,750 37,500 56,250 75,000 93,750 187,500 281,250
400 20,000 40,000 60,000 80,000 100,000 200,000 300,000
425 21,250 42,500 63,750 85,000 106,250 212,500 318,750
450 22,500 45,000 67,500 90,000 112,500 225,000 337,500
475 23,750 47,500 71,250 95,000 118,750 237,500 356,250
500 25,000 50,000 75,000 100,000 125,000 250,000 375,000
50 100 150 200 250 500 750
Bearingdiameter(mm) Shaft SPEED RPM
Shaft SPEED RPM
1,000 1,250 1,500 1,750 2,000 2,250
25,000 31,250 37,500 43,750 50,000 56,250 25
50,000 62,500 75,000 87,500 100,000 112,500 50
75,000 93,750 112,500 131,250 150,000 168,750 75
100,000 125,000 150,000 175,000 200,000 225,000 100
125,000 156,250 187,500 218,750 250,000 281,250 125
150,000 187,500 225,000 262,500 300,000 337,500 150
175,000 218,750 262,500 306,250 350,000 393,750 175
200,000 250,000 300,000 350,000 400,000 450,000 200
225,000 281,250 337,500 393,750 450,000 506,250 225
250,000 312,500 375,000 437,500 500,000 562,500 250
275,000 343,750 412,500 481,250 550,000 618,750 275
300,000 375,000 450,000 525,000 600,000 675,000 300
325,000 406,250 487,500 568,750 650,000 731,250 325
350,000 437,500 525,000 612,500 700,000 787,500 350
375,000 468,750 562,500 656,250 750,000 843,750 375
400,000 500,000 600,000 700,000 800,000 900,000 400
425,000 531,250 637,500 743,750 850,000 956,250 425
450,000 562,500 675,000 787,500 900,000 1,012,500 450
475,000 593,750 712,500 831,250 950,000 1,068,750 475
500,000 625,000 750,000 875,000 1,000,000 1,125,000 500
1,000 1,250 1,500 1,750 2,000 2,250
Bearingdiameter(mm)
Shaft SPEED RPM
Shaft SPEED RPM

12. Now refer to chart. In this example we have an anti friction bearing with 100,000 DN @
between 80 oC and 90 oC, so the viscosity requirement is between ISO 150 and ISO 320.
You can recalculate on this slide by double clicking the embedded excel sheet & entering
new temperature
Greases Selection techniques - operating speed/viscosity
A/ Fbearings A/ Fbearings
Speed factor (DN) 0 o
C - 30 o
C 30 o
C - 60 o
C 60 o
C - 80 o
C 90 o
C - 120 o
C Speed factor (DN)
= Bearing bore (mm) X
RPM
R&O ISO Grade R&O ISO Grade R&O ISO Grade R&O ISO Grade
= Bearing bore (mm) X
RPM
10,000 32-68 100 320 1000 10,000
25,000 32 100 320 460 25,000
50,000 22-32 68 220 460 50,000
75,000 22 46 220 320 75,000
100,000 22 46 150 320 100,000
250,000 10 32 100 220 250,000
> 250,000 10 32 100 220 > 250,000
= Bearing bore (mm) X
RPM
R&O ISO Grade R&O ISO Grade R&O ISO Grade R&O ISO Grade
= Bearing bore (mm) X
RPM
Speed factor (DN) 0 o
C - 30 o
C 30 o
C - 60 o
C 60 o
C - 80 o
C 90 o
C - 120 o
C Speed factor (DN)
A/ Fbearings A/ Fbearings
Approximate operating temperature range
Approximate operating temperature range

13. OK, that’s the simple method, now lets explore SKF’s more sophisticated method
SKFs adjusted bearing life formula … Lna = a1 a2 a3 (C/P)
p
where
C = Dynamic load rating
P = Dynamic bearing load
p = Exponent depending of bearing type
a1 = Life adjustment factor for reliability
a2 = Life adjustment factor for material
a3 = Life adjustment factor for operating conditions
Greases Selection techniques - operating speed/viscosity

14. Greases – Selection techniques - operating load
When loads are heavy & speed is low to medium, it can be an advantage to increase base
fluid viscosity & select a lubricant with AW & EP additives
It may also be an advantage to select an adhesive thickener & additives to prevent the
lubricant being squeezed out of the bearing
When shock loads are present & speed is low to medium, it can be an advantage to increase
base fluid viscosity, select a lubricant with AW & EP additives & utilise solid film addiitves to
protect against breaking through the fluid film
It will also be an advantage to select an adhesive thickener (e.g lithium calcium) & tackiness
additives to prevent the lubricant being squeezed out of the bearing
Greases – Selection techniques – shock load

15. Greases – Selection techniques - operating environment
Where environmental contamination is present (heat, dust, water, chemicals, others) the
primary selection criteria is the thickener, that the thickener may resist these contaminants.
For wet applications – use a thickener that will resist water wash-out
For hot applications applications – use a thickener & base fluid combination that will resist
radiant or inherent heat
For dusty applications – use a thickener that is very adhesive & that will form a seal to
prevent contaminant entry past the seals
For very dusty & applications where corrosives, scales & water are present– use an
application system that will ensure that grease flows past the seals to prevent ingress of
contaminants (e.g, increase grease application volume or utilise single point lubricators
(Tactic)

16. Greases – Selection techniques – process logic
When we have many products to choose from, the easiest and most accurate method is to
eliminate those which are not perfectly suitable.
To quote from Conan Doyle’s Sherlock Holmes “If you eliminate the impossible, then
whatever is left, no matter how improbable, must be the truth”
For our purposes (with some artistic license taken)
“If you eliminate the unsuitable greases, then whatever is left, no matter how improbable,
must be fit for purpose greases”