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GREASE READY REFERENCE
ABBREVIATIONS
ASTM
American Society for Testing and Materials
ISO
International Standards Associations
FDA
Food and Drug Administration
JIS
Japan Industry Standard
NLGI
National Lubricating Grease Institute
OEM
Original Equipment Manufacturer
SAE
Society of Automotive Engineers
AGMA
American Gear Manufacturers Association
Source :NTN BEARING CORPORATION
ABBREVIATIONS
ASTM
American Society for Testing and Materials
ISO
International Standards Associations
FDA
Food and Drug Administration
JIS
Japan Industry Standard
NLGI
National Lubricating Grease Institute
OEM
Original Equipment Manufacturer
SAE
Society of Automotive Engineers
AGMA
American Gear Manufacturers Association
Source :NTN BEARING CORPORATION
Relubrication Guidelines
It cannot be stated strongly enough that when relubricating a bearing unit it is essential to choose a clean lubricant compatible with the grease already in the bearing.
Whether or not different kinds of grease may be mixed depends on the thickening agents used in making the grease. Mixing different types of grease can affect key properties and alter the grease’s performance. If these key properties are diminished, the grease can become ineffective, leading to premature bearing failure. (Refer to Table 1 for further information.)
Pump the grease gun once prior to connecting it to the fitting to purge the nozzle of any contaminants that may have accumulated and wipe it with a clean towel. The grease fitting also merits inspection for contaminants and should also be wiped clean.
Taking these precautionary measures to prevent the introduction of contaminants into the bearing will help ensure the proper operation of the bearing and performance to and beyond the rated life of the bearing.
Table 1: Grease thickener compatibility
It cannot be stated strongly enough that when relubricating a bearing unit it is essential to choose a clean lubricant compatible with the grease already in the bearing.
Whether or not different kinds of grease may be mixed depends on the thickening agents used in making the grease. Mixing different types of grease can affect key properties and alter the grease’s performance. If these key properties are diminished, the grease can become ineffective, leading to premature bearing failure. (Refer to Table 1 for further information.)
Pump the grease gun once prior to connecting it to the fitting to purge the nozzle of any contaminants that may have accumulated and wipe it with a clean towel. The grease fitting also merits inspection for contaminants and should also be wiped clean.
Taking these precautionary measures to prevent the introduction of contaminants into the bearing will help ensure the proper operation of the bearing and performance to and beyond the rated life of the bearing.
Table 1: Grease thickener compatibility
Table key
Circle: Mixing greases will not produce any appreciable change in properties
Square: Mixing greases may produce considerable variation in properties
Triangle: Mixing greases will cause drastic changes in properties
As for the quantity of lubricant used, most applications require only two pumps of grease. This is an instance where more is not better. Over packing the bearings during relubrication should be avoided. Too much grease may create a "churning" action within the bearing, which in turn results in the bearing running hotter. This leads to premature deterioration of the grease and ultimately bearing failure.
ROLLING ELEMENT BEARINGS FAILURE INVESTIGATION
Rolling element bearings may fail for many reasons. Research by expert engineers have determine the cause of failures through experiential tests and have been carefully documented.
The data base documents failures of rolling element includes :
Circle: Mixing greases will not produce any appreciable change in properties
Square: Mixing greases may produce considerable variation in properties
Triangle: Mixing greases will cause drastic changes in properties
As for the quantity of lubricant used, most applications require only two pumps of grease. This is an instance where more is not better. Over packing the bearings during relubrication should be avoided. Too much grease may create a "churning" action within the bearing, which in turn results in the bearing running hotter. This leads to premature deterioration of the grease and ultimately bearing failure.
ROLLING ELEMENT BEARINGS FAILURE INVESTIGATION
Rolling element bearings may fail for many reasons. Research by expert engineers have determine the cause of failures through experiential tests and have been carefully documented.
The data base documents failures of rolling element includes :
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When machines experience a failure, your first approach is to collect technical information and failure history.
Take an OVERVIEW rather than the NARROWER approach of investigating the apparent immediate problem and carry out a macro-analysis.Definition Of Terms Relating To Lubricating Grease
DROPPING POINT
The drop point of a particular type of grease is that temperature at which the first drop of liquid separates when the grease is heated under prescribed conditions.
PENETRATION
The measure which indicates the softness or hardness of a grease. The NLGI has developed a numerical scale to classify the consistency of grease based upon their worked 60-stroke penetration values.
Take an OVERVIEW rather than the NARROWER approach of investigating the apparent immediate problem and carry out a macro-analysis.Definition Of Terms Relating To Lubricating Grease
DROPPING POINT
The drop point of a particular type of grease is that temperature at which the first drop of liquid separates when the grease is heated under prescribed conditions.
PENETRATION
The measure which indicates the softness or hardness of a grease. The NLGI has developed a numerical scale to classify the consistency of grease based upon their worked 60-stroke penetration values.
NLGI GRADE NUMBERS / PENETRATION
NLGI Grade |
ASTM worked Penetration, 60 stroke |
Penetration and Typical Methods of Application |
000 |
445 - 475 |
Very Fluid; used in centralized systems |
00 |
400 - 430 |
Fluid; used in centralized systems and enclosed gear boxes |
0 |
355 - 385 |
Semi-Fluid; used in centralized systems |
1 |
310 - 340 |
Very soft; used in grease gun, centralized systems or normal application |
2 |
265 - 295 |
Soft; used in grease gun, centralized systems or normal application |
3 |
220 - 250 |
Medium Hard; used in grease gun or normal application |
4 |
175 - 205 |
Hard; used in grease gun or normal application |
5 |
130 - 160 |
Very Hard; used for special application |
6 |
85 - 115 |
Extremely Hard; block grease; used in open grease cellars or special application |
EXTREME PRESSURE (EP) ADDITIVE
Chemical compound imparting extreme pressure characteristics to a lubricant with the objective of reducing wear under conditions where rubbing or sliding accompanies high contact pressures, as in heavily loaded applications.
MOLYBDENUM DISULPHIDE (MOS2) AND GRAPHITE
A very effective solid lubricant that is used for back-up lubrication in extra high temperature and high load applications.
Chemical compound imparting extreme pressure characteristics to a lubricant with the objective of reducing wear under conditions where rubbing or sliding accompanies high contact pressures, as in heavily loaded applications.
MOLYBDENUM DISULPHIDE (MOS2) AND GRAPHITE
A very effective solid lubricant that is used for back-up lubrication in extra high temperature and high load applications.