Mining loads are not gentle. A primary crusher shaft bearing sees impact spikes several times rated load; excavator bucket pins hammer and twist under full stall torque; vibrating screens shake their own frames apart over years. Add abrasive dust and high-pressure washdown water, and you have the most hostile lubrication environment in industry.
What shock load does to a grease film
Under steady load, a grease’s base oil maintains a hydrodynamic film on the raceway. Under shock load, that film is squeezed out in milliseconds, and metal contacts metal briefly – a phenomenon called boundary lubrication. The grease must contain extreme-pressure (EP) additives that react chemically with the steel surface at that contact instant, forming a sacrificial layer that prevents welding and scoring.
The EP toolbox
Sulfur-phosphorus EP additives: The standard chemistry. Effective across a wide temperature window, works in most lithium EP grades. Our Black EP line carries a 4-ball weld load above 3,100 N (ASTM D2596).
Molybdenum disulfide (MoS2): A solid lubricant suspended in the grease – typically 3% in our moly grades. MoS2 plates onto the metal surface and shears easily, providing lubrication exactly when the oil film fails. Ideal for sliding contacts: bucket pins, bushings, fifth wheels. Note: avoid MoS2 in rolling bearings running wet – it can abrade with the water present.
Calcium sulfonate: Naturally high EP capacity without additives, plus the best water resistance in the industry. The premium answer for wet, shock-loaded positions.
Matching grade to position
| Position | Recommendation | Why |
|---|---|---|
| Crusher main shaft | Lithium complex EP, NLGI 2 | Shock + moderate heat |
| Excavator bucket pins | Lithium EP + 3% MoS2, NLGI 2 | Sliding, shock, slow |
| Vibrating screen bearings | Polyurea or lithium complex, NLGI 3 | Vibration flings soft grease |
| Wet slurry pumps | Calcium sulfonate complex, NLGI 2 | Water + impact |
| Conveyor idlers | Lithium EP, NLGI 2, low cost | High quantity, moderate duty |
Relubrication is the other half of survival
Mining maintenance teams under-lubricate far more often than they over-lubricate – the schedule exists but the shut-down windows do not. Automating what you can (single-point lubricators on remote crusher bearings) and making pin grease-ups part of the shift routine, not the weekly routine, moves bearing life dramatically.
We export to mining operations in 20+ countries and can share reference setups for your equipment type. Black EP and moly samples ship free for bench and field trials.