NLGI grade is a measurement of the relative hardness of a grease used for lubrication, The softer the grease, the lower the number. The following table shows the classification of grease consistency:
| NLGI Grade | Appearance at room temperature 25℃ | Food Analogy |
|---|---|---|
| 000 | Very fluid | Ketchup |
| 00 | Fluid | Applesauce |
| 0 | Semi Fluid | Brown Mustard |
| 1 | Very soft | Tomato Paste |
| 2 | Soft | Peanut Butter |
| 3 | Medium hard | Vegetable Shortening |
| 4 | Hard | Frozen Yogurt |
| 5 | Very hard | Smooth Pate |
| 6 | Extremely hard | Cheddar Cheese Spread |
Measuring the consistency of lubricating greases by the penetration of a cone of specified dimensions, mass, and finish. The penetration is measured in tenths of a millimetre.
Thickener is a substance added to a liquid to make it firmer, grease composition including thickener, base oil and additive. There are numerous types of thickener for grease making. (soap thickener produced by Toyo Grease including calcium, lithium, calcium sulfonate, aluminium complex, lithium complex) (Non-soap thickener produce by Toyo Grease including clay & silica)
Calculated from the time it takes oil to flow from the starting point to the stopping point at 100°C. The higher the value, the thicker the base oil used to produce the lubricating grease.
Temperature at which a grease sample, when heated, will begin to flow through an opening. The higher dropping point, the better high temperature properties.
Measurement for the change of viscosity with variations in temperature. The lower the Viscosity Index, the greater the change of viscosity of the oil with temperature. It is used to characterize viscosity changes with relation to temperature in lubricating oil.
Standard measurement to determines the Wear Preventative (WP) and Extreme Pressure (EP) characteristics of lubricating oils and greases in sliding steel-on-steel applications. The higher the Four Ball EP Weld Load, the better the load carrying performance of the grease.
Suitable working range of the grease, it goes between the low temperature performance limit and the high temperature performance limit.
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 used in the bearing.
Whether or not different kinds of grease may be mixed depends on the thickening agents used in making 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.
Taking 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.
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.
As for the quantity of lubricant used, most applications require only two pumps of grease. This is an instance where more is not better. Overpacking the bearings during re-lubrication 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.
Grease filling quantity calculation method: DN Value
1. Inner race ID in MM x RPM
2. Size of bearing : Inner race (In MM)
3. RPM : Rotation per minutes (Example: 1,000 RPM)
| Speed | Lubrication |
|---|---|
| Low speed DN Value below 50,000 |
Bearing filled to capacity (Full load) |
| Medium speed DN Value between 50,000 – 200,000 |
Bearing filled to 50% - 70% |
| High speed DN Value above 200,000 |
Bearing filled to 30% - 40% |
| Extreme speed | Bearing filled to 10% - 15% |
