Page 314 - The Tribology Handbook

c4 Greases

A grease may be defined as solid to semi-fluid lubricant Tables 4.1,4.2 and 4.3 illustrate some of the properties of
consisting of a dispersion of a thickening agent in a lubricat- greases containing these three types of fluid. All values and
ing fluid. The thickening agent may consist of e.g. a soap, remarks are for greases typical of their class, some pro-
a clay or a dyestuff. The lubricating fluid is usually a prietary grades may give better or worse performance in
mineral oil, a diester or a silicone. some or even all respects.

TYPES OF GREASE

Tabb 4.1 Grease containing mineral oils

Min. drop Min. Max. Available with
Soap base or pt. "C (OF) usable usable Rust extreme
thickener ASTM D 556 temp. temp. protection pressure Use Cost Oj'icial speciJication
IP 132 "C("F) "C("F) additiue

Lime (calcium) 90 (190) -20 (0) 60 (140) - Yes General Low BS 3223
purpose
Lime (calcium) 99.5 (210) -20 (0) 80 (175) (Some- Yes General Low BS 3223
heat stable or -55 (-65) * times) purpose DEF STAN 91-17 (LG 280)
140 (280) * and
rolling DEF STAN 91-27 (XG 279)
bearings MIL--G- 10924B

Sodium 205 (400) 0 (32) 150-175 Yes No Glands, seals Low -
(conventional) (30c~350) low-medium
speed rolling
bearings
Sodium and 150 (300) -40 (-40) 120-150 Yes No High-speed Medium DEF 2261A (XG 271)
calcium (250-300) rolling MIL-L-7711A
(mixed) bearings

Lithium 175 (350) -40 (-40) 150 (300) Yes Yes All Medium DEF STAN 91-12 (XG 271)
rolling DEF STAN 91-28 (XG 274)
bearings MIL-L7711A
Aluminium 200 (390) -40 (-40) 160 (320) Yes Mild EP Rolling Medium/ -
Complex bearings high

Lithium Complex 235 (450) -40 (-40) 175 (350) Yes Mild EP Rolling Medium -
bearings
Clay None -30 (-20) 205 (400)* Poor Yes Sliding Medium -
friction

* Depending on conditions of service.

Although mineral oil viscosity and other characteristics viscosities and other characteristics of the mineral oil, which
of the fluid have been omitted from this table, these play should be observed. Apart from these requirements, the
a very large and often complicated part in grease perform- finished characteristics of the grease, as a whole, should be
ance. Certain bearing manufacturers demand certain regarded as the most important factor.

C4.1