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Unformatted text preview: ality. Product literature also gives the oil type (i.e., paraffinic, naphthenic, residual
compounded, or synthetic).
(b) Producer specifications. Producer specifications amount to a certification that the product meets
or exceeds listed physical characteristics in terms of specific test values. The magnitude of chemical
impurities may also be given. Producers vary somewhat in the amount of information in their
specifications. However, kinematic viscosity (centistokes) at 40 and 100 EC (104 and 212 EF ), SUS
(saybolt viscosity) at 37 and 98 EC (100 and 210 EF ), API gravity, pour point, and flash point are
generally listed. Other physical and chemical measurements may also be given if they are considered to
influence the intended use.
b. Grease classifications.
13-3 EM 1110-2-1424
28 Feb 99 (1) Characteristics. Grease is classified by penetration number and by type of soap or other thickener.
Penetration classifications have been established by NLGI and are given in Chapter 5. ASTM D 217 and
D 1403 are the standards for performing penetration tests. A penetration number indicates how easily a
grease can be fed to lubricated surfaces (i.e., pumpability) or how well it remains in place. Although no
method exists to classify soap thickeners, the producer indicates which soap is in the product. The type of
soap thickener indicates probable water resistance and maximum operating temperature and gives some
indication of pumpability. Although these are important factors, they are not the only ones of interest.
These simple classifications should be regarded as starting requirements to identify a group of appropriate
grease types. The final selection must be made on the basis of other information provided in the producer's
specifications. Viscosity of the oil included in a grease must also be considered.
(2) Producer’s product data for grease. Producers also provide information and specifications for
grease in brochures, pamphlets, handbooks, or on the product container or packaging. Grease
specifications normally include soap thickener, penetration, included oil viscosity, and dropping point. The
producer may also include ASTM test information on wear, loading, lubrication life, water washout,
corrosion, oil separation, and leakage. Grease additives are not usually stated except for solid additives
such as molybdenum disulfide or graphite, or that an EP additive is included. If EP or solid additives are
used, the producer will often state this emphatically and the product name may indicate the additive.
13-3. Principles of Selection
a. Manufacturer recommendations.
(1) The prime considerations are film thickness and wear. Although film thickness can be calculated,
the wear properties associated with different lubricants are more difficult to assess. Lubricants are
normally tested by subjecting them to various types of physical stress. However, these tests do not
completely indicate how a lubricant will perform in service. Experience has probably played a larger role
than any other single criterion. Through a combination of testing and experience, machine manufacturers
have learned which classes of lubricants will perform well in their products.
(2) Professional societies have established specifications and classifications for lubricants to be used in
a given mechanical application. For example, AGMA has established standard specifications for enclosed
and open-gear systems. These specifications have been developed from the experience of the association’s
membership for a wide range of applications. Thus, any manufacturer has access to the collective
knowledge of many con...
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- Spring '11