given to its selection and application as well as its condition while in use. FIST,
Lubrication of Powerplant
Equipment provides more information on lubricants and their use.
The equipment manufacturer should provide specific information on the type of lubricant and
periodic maintenance recommended for a particular application.
Oil lubrication can take many forms, from a simple squirt oil can to a complex
circulating system. Regardless of the method by which the oil is applied, the intent is the same,
and that is to keep a lubricant film between moving surfaces. For successful lubrication, it is
critical that the proper oil be chosen, properly applied, and kept clean and uncontaminated.
While it is beneficial to have as few types of oil in stock as possible, there is no one all purpose oil
that can be used in all applications. Various additives, such as emulsifiers, rust and corrosion
inhibitors, detergent and dispersants are added to oil to enhance their performance for a given
application. Characteristics that may be desirable in one case may be very undesirable in another.
For example, emulsifiers added to motor oil allow the oil to hold water in an emulsion until the
engine's heat can boil it away. In bearing lubrication, where there is not sufficient heat to
evaporate the water, the oil must be capable of readily separating from water.
Grease is a lubricant consisting of a lubricating oil combined with a
thickening agent. The base oil makes up 85 to 95 percent of the grease and performs the actual
lubrication. The thickening agent, usually some type of soap, determines many of the
characteristics of a grease such as heat resistance, water resistance, and cold weather pumpability.
Various additives may also be added to improve performance.
Overheating and subsequent failure of grease lubricated bearings caused by over lubrication is a
common problem. The idea that more is better coupled with the fact that it is usually difficult to
determine the actual amount of grease in a bearing housing, causes many bearings to be "over
Ideally, a grease lubricated bearing should be "packed" by hand so that the bearing housing is
approximately one-third full of grease. When grease is applied using a grease gun, the relief plug,
if so equipped, should be removed so that as the new grease is applied, all of the old grease is
purged from the bearing housing. The unit should be operated approximately 30 minutes before
the plug is replaced to allow excess grease to escape. If the bearing housing doesn't have a relief
plug, grease should be added very infrequently to prevent over lubrication.
Many of the soap bases used in making grease are incompatible. Mixing two different types of
grease will many times result in a mixture inferior to both of the component greases. As a general
rule, different greases should not be mixed. If it becomes necessary to change the type of grease
used on a piece of equipment, the bearing housing should be completely disassembled and
thoroughly cleaned to remove all the old grease. If this is not possible, as much of the old grease
as possible should be flushed out by the new grease during the initial application, and the greasing