Understanding Grease - NLGI Grades
Understanding NLGI from 000 to 6 to classification of greases.
The consistency is a measure of the hardness or softness of the grease, which influences its suitability for specific applications. The grades are determined by the penetration of a standardized cone into the grease, measured in tenths of a millimetre after five seconds of penetration.
Grease grades explained with implications on pump selection
| NLGI Grade | Worked Penetration After 60 Strokes at 25℃ (0.1mm) | Appearance | Common Application |
|---|---|---|---|
| 000 | 445-475 | Fluid | Gearboxes (low temperature use) |
| 00 | 400-430 | Fluid | Gearboxes (low temperature use) |
| 0 | 355-385 | Very Soft | Centralised lubrication systems |
| 1 | 310-340 | Soft | General purpose bearings |
| 2 | 265-295 | Moderately Soft | General purpose bearings |
| 3 | 220-250 | Semi-Fluid | High speed bearings |
| 4 | 175-205 | Semi-hard | Very high speed bearings |
| 5 | 130-160 | Hard | Low speed journal bearings |
| 6 | 85-115 | Very Hard | Very low speed journal bearings |
NLGI #000 to #2: Soft Greases
NLGI 000, 00, and 0 greases are considered soft or semi-fluid. These greases have a high degree of fluidity, making them suitable for applications where low resistance to deformation is required. Imagine the consistency of heavy cream or mayonnaise; these soft greases exhibit a similar flow and can easily conform to irregular surfaces.
NLGI 1 and 2 greases are softer than their higher-numbered counterparts but still have enough structure to resist dripping or running excessively. Think of the consistency of peanut butter or toothpaste – these greases exhibit a moderate level of firmness.
NLGI #3: Medium Greases
NLGI 3 greases have a medium consistency and exhibit a smooth, butter-like texture. Picture the feel of margarine or vegetable shortening; these greases provide a good balance between fluidity and structure. They are commonly used in applications where a more stable and adhesive grease is required.
NLGI #4 to #6: Firm to Hard Greases
NLGI 4, 5, and 6 greases are considered firm to hard. These greases have a high degree of structure, providing excellent resistance to deformation. Picture the consistency of hard cheese, like Parmesan or Cheddar – these greases are relatively stiff and maintain their form under pressure.
Understanding NLGI grades is crucial for selecting the right lubricating grease for specific applications. By drawing comparisons to everyday products, we can demystify the concept of grease consistency and make informed choices based on the unique requirements of machinery and equipment. Whether you need a soft, flowing grease or a firm, structured one, the NLGI grading system provides a standardized way to communicate and choose the right lubricating grease for the job.
Pump and Reel Selection
Choosing the right pump and reel combination needs to be considered in conjunction with the goal that is to be achieved.
A high pressure pump will deliver much lower volumes of grease at a much higher pressure (suitable for direct greasing of bearings etc) eg: 50:1; 65:1 and 75:1 pumps.
A high volume pump will deliver much more volume of grease at a much lower pressure (suitable for bulk grease transfer etc) eg: filling of grease cartridges, centralised lube reservoirs etc.
There is a trade off between pressure and volume – where only one can be delivered at a time. If both are required, a compromise must be reached or a twin pump setup installed.