Grease Lubrication

Why grease lubrication?
Properties
Grease compatibility chart
NLGI Grease consistency grading
Why grease?
Greases are typically applied in areas where a continuous supply of oil cannot be retained, such as open bearings or gears. Factors to be considered when selecting a suitable grease are operating temperatures, water resistance, oxidation stability etc. The second factor, not less important, are the grease's characteristics, including viscosity and consistency.

A lubricating grease consists of a base oil, performance additives and a thickener which forms a matrix that retains the oil in a semisolid state. Most grease thickeners are soaps, i.e. lithium, calcium, or aluminum soap. Complex soap greases have superior temperature resistance and are commonly usable up to 180ºC, at which the mineral oil vaporizes. A smaller number of greases, restricted to very special applications, are manufactured with non-soap thickeners such as organoclays, polyurea or silica compounds.

Grease is the most widely used lubricant for roller bearings and low velocity applications, mainly because grease type lubricants are relatively easy to handle and require only the simplest sealing devices.
Grease properties
Lithium
 Calcium
conv.		 Calcium
anhyd.		 Al
 Lithium
complex		 Calcium
complex		 Aluminum
complex		 Polyurea
 Organo Clay
Dropping point 177-204 96-104 135-143 110 260 260 260 243 260
Max. Temp. 135 93 110 79 177 177 177 177 177
Water resistance o/++ +/++ ++ ++ +/++ o/++ +/++ +/++ o/++
Oxidation stability o/++ -/++ o/++ ++ o/++ -/+ o/++ +/++ +
Rust protection -/++ -/++ -/++ +/++ o/++ o/++ +/++ o/++ -/++
Pump
ability		 o/++ +/++ o/++ - +/++ o/+ -/o +/++ +
EP properties v v v - v v v v -
Grease compatibility chart
　 Lithium
complex		 Lithium Al.
Complex		 Calcium
complex		 Barium Sodium Bentone Silica
gel		 Polyurea
Lithium complex - v x v x x x v v
Lithium v - x v x x x v v
Al.complex x x - x x x x v x
Calcium complex v v x - v x x x x
Barium x x x v - x x v x
Sodium x x x x x - x x x
Bentone x x x x x x - v x
Silica gel v v v x v x v - x
Polyurea v x x x x x x x -
NLGI Grease Classification (National Lubricating Grease Institute)
The consistency of industrial greases are classified by the distance in tenths of a millimeter, that a standard cone penetrates a sample of the grease under standard conditions at 25ºC

NLGI Consistency (Grade no.)

ASTM Worked Penetration at 25ºC (Penetration in 0.1 mm)

 Appearance Consistency food analog

000

445 - 475

 fluid cooking oil

00

400 - 430

 semi-fluid applesauce

0

355 - 385

 very soft mustard

1

310 - 340

 soft tomato paste

2

265 - 295

 "normal" grease peanut butter

3

220 - 250

 firm vegetable shortening

4

175 - 205

 very firm frozen yogurt

5

130 - 160

 hard smooth pate

6

85 - 115

 very hard cheddar cheese

NLGI grades 0, 1 and 2 are applied in highly loaded gear transmissions, grades 1 through 4 are often applied in rolling bearings where grade 2 is the most common.