Tools & Materials Required
Safety Notes
- Avoid mixing incompatible greases -- purge old grease completely before switching
- Wear nitrile gloves when handling industrial greases
- Store grease containers sealed to prevent moisture and dust contamination
1. Understanding Grease Composition
Industrial grease consists of three components: base oil (70--90%), thickener (5--20%), and additives (1--10%). Each component impacts bearing performance differently.
Base Oil Types
| Base Oil | Temperature Range | Best For | Common Products |
|---|---|---|---|
| Mineral Oil | -20 C to +120 C | General purpose, cost-effective | SKF LGMT 2, FAG Arcanol L135V |
| Synthetic PAO | -40 C to +150 C | Wide temperature range, long life | SKF LGLT 2, Klober Isoflex NBU 15 |
| Synthetic Ester | -60 C to +180 C | Extreme conditions, food-grade options | SKF LGHP 2 |
| Silicone | -50 C to +200 C | Very high temperatures, low loads only | Specialty applications |
2. NLGI Consistency Grades
The NLGI (National Lubricating Grease Institute) scale rates grease consistency from 000 (fluid) to 6 (solid block). Most bearing applications use NLGI 2.
| NLGI Grade | Consistency | Application |
|---|---|---|
| 0 | Very soft | Centralized lubrication systems, low-temp |
| 1 | Soft | Large bearings, vertical shafts, low-speed |
| 2 | Medium (standard) | General purpose -- 90% of bearing applications |
| 3 | Firm | High-speed spindles, vertical applications with leakage risk |
3. Thickener Compatibility Matrix
Mixing incompatible thickener types causes grease softening, hardening, or separation -- all of which lead to bearing failure. Always purge the old grease completely when switching products.
| Lithium | Lithium Complex | Polyurea | Calcium Sulfonate | |
|---|---|---|---|---|
| Lithium | Compatible | Compatible | Incompatible | Borderline |
| Lithium Complex | Compatible | Compatible | Incompatible | Borderline |
| Polyurea | Incompatible | Incompatible | Compatible | Incompatible |
| Calcium Sulfonate | Borderline | Borderline | Incompatible | Compatible |
4. Re-Lubrication Interval Calculation
The SKF re-lubrication interval formula provides a science-based approach to determining when bearings need fresh grease:
Where:
tf = re-lubrication interval (operating hours)
K = bearing type factor (1.0 for ball, 0.5 for cylindrical roller, 0.17 for tapered roller)
n = rotational speed (rpm)
dm = mean bearing diameter = (d + D) / 2 in mm
Correction Factors
- Temperature: Halve the interval for every 15 C above 70 C operating temperature
- Contamination: Reduce by 50% in dusty/humid environments (common in UAE construction and cement)
- Vibration: Reduce by 50% for equipment with significant vibration (crushers, screens, mills)
- Vertical shaft: Reduce by 50% due to grease migration under gravity
5. Correct Grease Quantity
Over-greasing is as damaging as under-greasing. The standard formula for re-lubrication quantity:
Where:
Gp = grease quantity in grams
D = bearing outside diameter in mm
B = bearing width in mm
For initial fill (new bearing installation), grease should fill 30--50% of the bearing's free internal space. Over-filling causes churning, temperature rise, and accelerated grease degradation.
6. Automatic Lubrication Systems
For critical or hard-to-reach bearings, automatic lubrication eliminates human error and ensures consistent grease delivery. Types include:
- Single-point lubricators (SKF TLSD, LAGD series) -- battery or gas-driven, mount directly on the bearing housing. Ideal for 1--12 month refill cycles.
- Multi-point centralized systems -- pump-driven with distribution lines to 10--200+ points. Used in cement plants, conveyor systems, and large rotating equipment.
- Progressive systems -- each lubrication point gets a measured dose sequentially. Blockage at one point halts the entire system, providing a built-in fault alert.
Pro Tips
- 1Keep a grease log per bearing point -- record date, quantity, product used, and operator name
- 2Calibrate grease gun output annually; most technicians over-grease by 40--60% without calibration
- 3In UAE summer conditions, schedule re-lubrication during cooler hours (early morning) to avoid grease thinning during application
Important Warnings
- Never top up a failed bearing with fresh grease and assume it is repaired -- investigate the root cause
- Do not use a grease gun with unknown residual grease; dedicated guns per grease type prevent cross-contamination
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