The Mill Liner Selection Decision
Mill liner selection is one of the highest-impact maintenance decisions in mineral processing. Liners represent a significant ongoing cost β?a large SAG mill may consume $1β? million USD per year in liner costs. The difference between rubber and steel liner performance in your specific application can mean the difference between 12-month and 30-month liner life, with corresponding differences in total cost and mill availability.
How Rubber and Steel Liners Wear Differently
Steel Liners
Steel liners (typically chromium-molybdenum alloy steel, 400β?50 BHN hardness) wear by metal removal through abrasion and impact. Their wear resistance increases with hardness, but very hard steels are brittle and prone to cracking under high-energy impact. Steel liners perform well when the ore is hard and the grinding media impacts are severe.
Rubber Liners
Rubber liners wear by elastic deformation and surface material removal. The rubber absorbs impact energy elastically and recovers β?rather than wearing away. This mechanism is most effective when ore hardness is moderate and grinding media impacts are not excessively severe. Rubber is completely unsuitable when grinding media energy is so high that it exceeds the rubber's elastic recovery capacity, causing fatigue tearing.
Decision Criteria: Bond Work Index
The Bond Work Index (BWI) is the most commonly used criterion for rubber vs steel liner selection:
| Bond Work Index | Recommended Liner | Ore Examples |
|---|---|---|
| <10 kWh/t (soft) | Rubber preferred | Limestone, bauxite, soft coal |
| 10β?5 kWh/t (medium) | Rubber or composite | Copper porphyry, some gold ores |
| 15β?0 kWh/t (hard) | Composite or steel | Hard gold ore, magnetite, granite |
| >20 kWh/t (very hard) | Steel required | Quartzite, taconite, hard BIF |
Advantages of Rubber Liners
- Weight: 75% lighter than steel β?faster installation, lower crane requirements, less mill bearing load
- Installation time: Rubber liner changeout takes 40β?0% less time than steel
- Noise reduction: 10β?5 dB(A) reduction β?significant for worker health and community relations
- No sparking: Eliminates fire risk from grinding media sparks β?important in some process environments
- Service life (soft ore): 2β?Γ longer than steel in appropriate applications
When Steel Liners Are Required
- Very hard ore (BWI >18 kWh/t)
- Very large grinding media (>100mm balls in ball mills, >125mm in SAG mills)
- Very high mill rotational speed causing excessive impact energy
- High-temperature process (above 80Β°C mill interior temperature)
- Chemical environment incompatible with rubber (strong acids, certain solvents)
π‘ Composite Liners: The Best of Both
Composite mill liners combine a rubber base (impact absorption, weight reduction) with steel or ceramic inserts at the high-wear lifting face. They are often the best solution for medium-hard ores (BWI 12β?8 kWh/t) where neither pure rubber nor pure steel delivers optimal performance. Service life typically falls between rubber and steel, with installation time and noise closer to rubber.
Need Expert Help With This Problem?
Send us photos and details. Our engineers respond within 24 hours with diagnosis and solution.
Get Free Technical Advice β?/a> π¬ WhatsApp