Why Ball Mill Liner Selection Matters
Ball mills are central to mineral-processing grinding circuits. Liners cover the shell and feed/discharge ends, serving two functions: protecting the steel shell from direct impact and abrasion by ore and grinding media, and controlling ball trajectories to optimize the grinding zone.
An unsuitable liner material or profile can affect charge motion, throughput, energy use, wear and shutdown planning. The extent must be established from operating data. This guide covers common materials and profiles, differences between SAG and ball mill applications, and documents to check during procurement and inspection. It does not replace the mill manufacturer's manual, liner drawings or site grinding trials.
For further guidance on crusher liners, see our Cone Crusher Wear-Part Selection Guide.
Liner Material Options
Material selection depends on ore abrasiveness, impact load, mill diameter, grinding stage (primary or regrind) and wet or dry operation. Four main material families are available.
High-Manganese Steel (Mn13Cr2, Mn18Cr2)
Manganese steel remains a standard liner material because of its work-hardening capacity. Repeated ball impact raises surface hardness from approximately 200 HBW in the annealed condition to 500–600 HBW, creating a wear-resistant surface over a tough core that resists fracture under heavy impact.
Mn13Cr2andMn18Cr2are common designations for high-manganese steels, but chemical limits and delivery condition must follow the applicable standard, contract and material certificate. Grade selection requires impact loads, ore abrasiveness, ball size, speed and the failure history of existing liners; mill diameter alone is insufficient.
High-Chromium Cast Iron (Cr26, Cr30)
High-chromium cast iron contains 20–30% chromium and forms hard chromium carbides (HV 1300–1800) in a martensitic matrix. This structure provides strong wear resistance in fine grinding with moderate impact.
Cr26 (25–28% chromium) is a standard grade for secondary and tertiary compartments. Cr30 (28–32% chromium) adds corrosion resistance for wet grinding of sulphide ores. It is widely used in copper and gold circuits where acidic slurry accelerates chemical wear.
Rubber Liners
Rubber liners can reduce system mass and noise in some wet-grinding, corrosive or regrinding applications. The reduction depends on the design and measurement conditions. Permitted ball size, temperature, mill dimensions and impact loads must be checked against the liner supplier's design and mill requirements; universal size or temperature limits are not a substitute for engineering review.
Composite / Metal-Capped Rubber Liners
Composite liners combine steel or alloy lifters with rubber backing, using metal for impact resistance and rubber for wear and corrosion protection. They are increasingly used in large SAG and primary ball mills where pure rubber cannot withstand impact but corrosion protection is needed.
| Material | Key Properties | Best-Suited Application | Relative Wear Life | Cost Index |
|---|---|---|---|---|
| Mn13Cr2 | Work-hardening, 500+ HBW | Primary compartment, moderate abrasion | 1.0x (baseline) | 1.0x |
| Mn18Cr2 | Enhanced hardening, 550+ HBW | Large mills, abrasive ore | 1.2–1.35x | 1.1x |
| Cr26 | Carbide hardness HV 1300+ | Secondary/tertiary compartments, fine grinding | 1.5–2.0x | 1.3x |
| Cr30 | Corrosion-resistant carbides | Wet grinding of sulphide ores | 1.6–2.1x | 1.4x |
| Rubber | Elastic, corrosion-resistant | Fine grinding/regrinding, corrosive slurry | 2.0–3.0x* | 1.2x |
| Composite | Metal + rubber combination | SAG / large ball mills | 1.8–2.5x | 1.5x |
*Rubber's life advantage applies to suitable duty: fine grinding and corrosive slurry. Under high impact, rubber wears faster than manganese steel.
Liner Profiles
Profile geometry governs ball lift and cascading/cataracting motion. The right profile improves grinding-zone efficiency while reducing liner wear and power consumption.
| Profile | Lifting Action | Preferred Position | Main Benefit |
|---|---|---|---|
| Wave | Moderate, cascading | Secondary/tertiary compartments | Even wear, low noise |
| Lifter bars | Strong, cataracting | Primary compartment | Maximum impact energy |
| Step | Consistent, interlocking | Primary compartment | Shell protection + lift |
| Shiplap | Moderate, overlapping | Small mills / intermediate positions | Easy installation |
| Osborn / classifying | Helical, classifying | Long mills | Optimized ball-size distribution |
Wave
Wave liners have a smooth, continuous undulating surface that provides moderate lift and reduces slip. They promote cascading and suit fine grinding in secondary and tertiary compartments where attrition dominates.
Lifter bars
Lifters control the lifting and fall trajectory of balls and slurry. Their height, angle, spacing and worn profile jointly affect impact, power and liner wear. Determine these dimensions from mill parameters, the ball-charge regime, liner drawings and trajectory analysis.
Step
Interlocking step liners form a continuous stepped surface around the circumference, giving consistent lift and shell protection. They are common in primary compartments where coarse feed up to 25 mm requires strong lifting of large balls into cataracting motion.
Shiplap
Shiplap liners overlap to protect the shell while providing moderate lift. They suit small mills or intermediate compartments that need balanced protection and lifting without the strong cataracting produced by high lifters.
Osborn / classifying
Osborn classifying liners use a helical profile to sort balls along the mill: larger balls move toward the feed end and smaller balls toward discharge. In long mills, this gradient improves efficiency by matching ball size to progressively finer ore.
SAG versus Ball Mill Liners
SAG and ball mills perform different roles in a grinding circuit, so their liners reflect different operating demands.
| Parameter | SAG Mill | Ball Mill |
|---|---|---|
| Feed Size | Up to 150 mm | Typically below 10 mm |
| Ball Size | 100–125mm | 25–75mm |
| Liner Thickness | 75–150mm | 50–100mm |
| Lifter Height | 75–200mm | 25–75mm |
| Recommended Materials | Mn18Cr2 / Mn22Cr2 | Mn13Cr2 / Cr26 / rubber |
| Typical Life | 4–8 months | 6–24 months |
SAG liners must withstand ore up to 150 mm and balls up to 125 mm diameter. This requires thicker plates, taller and stronger lifters, and tougher materials, typically Mn18Cr2 or Mn22Cr2. Ball mills handle smaller feed and balls, allowing thinner liners, finer profiles and, where impact permits, high-chromium iron or rubber.
Common Ball Mill Models and Liner Compatibility
Major mining-equipment manufacturers offer ball mills in many sizes. The table summarizes common models and recommended liner materials.
| Manufacturer | Model Series | Diameter Range | Typical Power | Recommended Liner Materials |
|---|---|---|---|---|
| Metso / Outotec | Ball mills (formerly Outotec) | 2.0–8.2m | 200–8,000 kW | Mn18Cr2 (primary), Cr26 (secondary) |
| FLSmidth | Ball mills (formerly FFE) | 1.5–7.9m | 100–7,000 kW | Mn13Cr2/Mn18Cr2, rubber |
| CITIC Heavy Industries | Ball Mill | 2.4–7.9m | 200–6,000 kW | Mn18Cr2，Cr26 |
Compatibility depends on shell diameter, liner bolt-hole layout and discharge type. For replacement liners, provide manufacturer, model and size, shell diameter and length, and the OEM part number from the original liner drawing.
Replacement Indicators
Early replacement wastes remaining life; late replacement risks shell damage and unplanned downtime. Monitor these indicators:
- Throughput falls by 10–15% — Worn liners lift less effectively, weakening grinding and allowing more under-ground material to discharge.
- Power consumption rises by 5–10% — A flattened profile requires more energy to maintain the same speed, indicating lower lifting efficiency.
- Product Size Distribution Shifts — P80 becomes coarser as worn liners fail to maintain the correct ball trajectories and grinding zone.
- Thickness in Critical Wear Zones Falls to 60–70% of Original — Measure with an ultrasonic thickness gauge during planned shutdowns.
- Visible Cracks, Wear-Through or Elongated Bolt Holes — Replace immediately to prevent shell damage.
- Increased Noise or Vibration — May indicate loose or broken liner bolts.
Critical production circuits need a wear-monitoring plan. Set measurement intervals according to site risk and maintenance windows; record liner profiles, bolt condition, throughput and power trends to forecast replacement. Evaluate any reduction in unplanned downtime using site records from before and after implementation.
Installation Practices
Correct installation matters as much as material and profile selection. Even high-quality liners perform poorly when installed incorrectly.
Before Installation
- Clean the Mill Shell Thoroughly — Remove all old backing compound, scale and debris.
- Inspect the Shell and Bolt Holes — Check for elongated or cracked bolt holes, which indicate shell wear, and repair as needed.
- Verify Liner Dimensions — Measure each liner against the OEM drawing before installation; reject deviations above 1.5 mm.
Installing the Liners
- Apply Backing Compound Correctly — Ensure full, void-free coverage to distribute load and prevent particles entering behind the liner.
- Tighten Liner Bolts to Specification — Use the mill manufacturer's torque values; insufficient torque causes loosening, while excessive torque may crack the liner.
- Install Lifters before Shell Plates — In multi-component systems, install lifters first to ensure correct interlocking.
- Follow the Correct Sequence — Work from feed to discharge, maintaining the correct overlap.
After Installation
- Allow Backing Compound to Cure Fully — Allow at least 12–24 hours, depending on compound type and ambient temperature.
- Run In the Liners — Run for 4–8 hours with reduced feed and ball charge to seat the liners.
- Retighten after Running In — Initial settling may loosen bolts; inspect and retighten all liner bolts after the run-in period.
Skipping the run-in is a common cause of premature failure. Initial seating distributes load across bolts and backing compound; without it, local stress may crack liners within the first 100 operating hours.
Frequently Asked Questions
How often should ball mill liners be replaced?
Ball mill liner replacement intervals depend on the ore, mill, ball charge, liner design and operating regime. Set replacement criteria using the manufacturer's minimum safe thickness, bolt and liner condition, throughput and power trends. Track both operating hours and cumulative tonnage rather than applying universal calendar intervals or percentage limits.
Which liner material suits my ball mill?
Material selection depends on the grinding stage, ore properties, impact loads, corrosive conditions, ball size and mill specification. High-manganese steel, high-chromium cast iron, rubber and composite designs each have application limits; the compartment or mill diameter alone cannot determine the choice.Contact our engineers , please also provide mill details, liner drawings, the ball-charge regime and wear records.
How do SAG and ball mill liners differ?
SAG liners are 50–100 mm thicker, with taller, stronger lifters for ore up to 150 mm and 125 mm balls. They typically use tougher Mn18Cr2 or Mn22Cr2. Ball mills handle feed below 10 mm and balls of 25–75 mm, allowing thinner liners, finer profiles and, where impact permits, high-chromium iron or rubber.
How should I choose a liner profile?
Match profile to grinding stage. Steps or high lifters give primary compartments strong cataracting impact on coarse feed. Waves support cascading and attrition in secondary and tertiary compartments. Consider Osborn/classifying profiles in long mills to maintain ball-size distribution; shiplap suits small mills or intermediate positions. Balance lift, power consumption and wear rate.
Putting the Selection Together
Ball mill liner selection requires a combined assessment of material properties, profile geometry, ore characteristics and production objectives. Once the material, profile, installation and monitoring plans are defined, calculate cost per tonne from baseline and trial data for throughput, energy use, life and downtime. Do not promise a fixed reduction without site evidence.
ANRANST manufactures OEM-specification replacement liners for Metso/Outotec, FLSmidth and CITIC Heavy Industries ball mills, with material certification and engineering support for material/profile optimization. Send mill specifications and OEM part references for a matched quotation.