Peças para Moinho SAG
Revestimentos para Moinho SAG | Carcaça, Extremidade e Grelhas | ATF
Peças para moinhos SAG: revestimentos, barras elevadoras e grelhas em cromo-molibdênio, aço liga e borracha-aço. Envie tamanho do moinho e dados do minério.
Complete Liner Solutions for SAG Mills
Semi-Autogenous Grinding (SAG) mills use the ore itself as grinding media, supplemented with a small steel ball charge (8–15%). The resulting combination of autogenous impact grinding and ball-assisted attrition makes SAG mills the workhorse of modern comminution circuits — processing run-of-mine ore from 300 mm feed to 10–25 mm product in a single stage. SAG mills are the largest rotating grinding equipment in mining, with diameters up to 12.2 m (40 ft) and drive powers exceeding 25 MW.
Every wear component in a SAG mill operates under extreme conditions: shell liners absorb the impact of ore lumps cataracting from over 5 m height, lifter bars control a combined charge weighing hundreds of tonnes, and grate panels must balance slurry discharge with pebble extraction. ATF engineers and manufactures the complete range of SAG mill liners, lifter bars, grate panels and discharge components to OEM specifications — with alloy grades, profile geometries and pebble port configurations optimised for your specific ore and grinding circuit.
ATF SAG mill liners — shell liners, high-profile lifter bars and pebble-ported grate panels in chrome-moly steel and bimetallic configurations, engineered for high-impact semi-autogenous grinding.
Semi-Autogenous Grinding Mechanism
Understanding how ore-on-ore impact, ball-assisted attrition and charge trajectory control work together explains why liner profile, lifter geometry and grate design directly determine grinding efficiency, energy consumption, throughput and cost per tonne ground.
Feed & Charge Lifting
Run-of-mine ore (up to 300 mm) enters the SAG mill through the feed trunnion along with recirculated pebbles. As the mill rotates at 70–78% of critical speed, high-profile lifter bars (200–350 mm) carry the combined charge of ore and steel balls upward along the shell wall. The lifter height and face angle determine the shoulder angle — how high the charge is lifted before detaching from the liner and beginning its descent toward the toe zone.
Impact & Attrition Grinding
Ore is reduced through two mechanisms: cataracting impact (large ore lumps and steel balls free-fall through the air and smash into the charge — fracturing coarse particles) and cascading attrition (ore tumbles down the charge surface — grinding by abrasion and inter-particle compression). The balance between these mechanisms is controlled by mill speed, lifter profile, ball charge level and ore competency. This dual grinding action enables SAG mills to process ROM ore in a single stage.
Discharge & Pebble Extraction
Ground slurry passes through grate panel apertures (10–40 mm), while critical-size pebbles (50–100 mm) are extracted through dedicated pebble ports (80–120 mm) and sent to a pebble crusher for further size reduction before being returned to the mill feed. Pulp lifter channels transport slurry from the grate face to the discharge trunnion. A trommel screen at the discharge classifies the product before it passes to the next stage — typically a ball mill or classification circuit.
SAG Mill Liners & Wear Components
A SAG mill requires five categories of wear and structural components. Each component page provides detailed material options, profile design guidance and OEM compatibility information for your specific mill.
Shell Liners
Protect the cylindrical shell from direct impact of large ore lumps and steel grinding media. SAG mill shell liners must withstand far higher impact energies than ball mill liners — ore pieces up to 300 mm impact the liner at high velocity during cataracting. High-lift and wave profile designs control the charge trajectory and grinding action.
End Liners
Protect the feed-end and discharge-end heads of the SAG mill. Feed-end liners incorporate the feed opening geometry and must withstand direct impingement of incoming coarse ore. Discharge-end liners integrate with the grate panel arrangement and must maintain correct geometry for grate support and pulp lifter alignment.
Lifter Bars
High-profile raised elements that lift the combined charge of ore and steel balls. SAG mill lifter bars are significantly taller than ball mill lifters (200–350 mm) to handle the larger, heavier charge. Lifter bar height, face angle and row spacing control the balance between impact grinding (cataracting) and attrition grinding (cascading) — directly determining throughput and energy efficiency.
Grate Panels
Perforated discharge panels that retain grinding media and oversize ore while passing ground slurry. SAG mill grates feature both fine apertures (10–40 mm) for product discharge and pebble ports (80–120 mm) for extracting critical-size pebbles that recirculate to a pebble crusher. Grate open area (8–25%) directly controls mill throughput capacity.
Additional Spares
Trunnion liners, pulp lifter channels, feed chutes, trommel screens and mill bolt hardware. These structural and flow-control components maintain mill geometry, protect high-value structural elements and manage material discharge. Trunnion liners in particular protect the expensive, non-replaceable mill trunnions from abrasive slurry wear.
Material Selection for SAG Mill Liners
SAG mill liner alloy selection is dominated by impact toughness — the energy of ore lumps and steel balls cataracting in a 6–12 m diameter mill is far higher than in a ball mill. Chrome-moly steel is the standard because it absorbs this energy without cracking. Bimetallic and high-chrome alloys are used selectively in lower-impact positions to extend wear life.
Chrome-Moly Steel
Cr-Mo alloy steel (325–450 BHN)
The industry standard for SAG mill shell liners and lifter bars — proven toughness to withstand the high-energy impact of large ore and 125 mm steel balls
Baseline (4–12 months typical)
Limitation: Higher wear rate than bimetallic or high-chrome in purely abrasive zones — but impact tolerance is essential in SAG mills
Bimetallic (Cr-Mo + HCWI)
Chrome-moly backing with high-chrome white iron face (600+ BHN)
High-wear zones in the lower shell where abrasion dominates — the hard white iron face resists abrasive wear while the chrome-moly backing absorbs impact energy
1.5–2.5× chrome-moly in suitable positions
Limitation: Higher cost than standard chrome-moly. White iron face can crack under extreme point-load impact from very large ore in the cataracting zone
High-Chrome White Iron
25–28% Cr (58–64 HRC)
Grate panels and discharge components where abrasion is high but direct media impact is limited. Not suitable for SAG mill shell liners or lifter bars
1.5–2× chrome-moly in grate positions only
Limitation: Very brittle under the high-energy impact loads in a SAG mill — will crack or shatter in shell or lifter positions
Ni-Hard / Alloy Iron
Ni-Cr alloy iron (550–650 BHN)
Grate panels, pulp lifter channels and discharge-end components where moderate impact resistance is acceptable
1.3–1.8× chrome-moly in discharge components
Limitation: Not recommended for shell liners or lifter bars in SAG mills — insufficient toughness for the high-energy cataracting impact zone
SAG Mill Alloy Selection Framework
Shell liners and lifter bars (all positions)? → Chrome-moly steel (400–450 BHN) — non-negotiable for SAG mill impact resistance
Lower shell liners in highly abrasive ore? → Bimetallic (Cr-Mo + HCWI face) for 1.5–2.5× life in the sliding wear zone
Grate panels and discharge components? → High-chrome white iron or Ni-Hard for maximum abrasion resistance in low-impact positions
End liners (feed and discharge heads)? → Chrome-moly steel (350–400 BHN) — moderate impact with good abrasion resistance
Contact ATF with your mill size, ore abrasion index (Ai), Bond work index (Wi), ball charge level and current liner performance data — we'll recommend the optimal alloy and profile combination for each position in your SAG mill.
Compatible SAG Mill Brands & Models
ATF manufactures aftermarket shell liners, lifter bars, end liners and grate panels to OEM dimensional and profile specifications for SAG mills from all major manufacturers. All liners are verified against original mill drawings before production. Dimensional tolerance: ±2 mm bolt hole positions, weight: ±3%.
Metso / Outotec
SAG mills from 6.1m to 12.2m diameter — including Nordberg and Outotec designs
Including legacy Nordberg, Svedala and Outotec SAG mill patterns
FLSmidth
SAG mills from 6.1m to 12.2m diameter — including Fuller-Traylor designs
Including ABON, Fuller-Traylor and legacy Allis-Chalmers SAG mill designs
Thyssenkrupp / Polysius
SAG mills from 6.0m to 11.6m diameter — Polysius and industrial grinding systems
ThyssenKrupp Industrial Solutions — large-diameter SAG mills for mining
CITIC
SAG mills from 6.1m to 12.2m diameter — large-scale mineral processing mills
CITIC Heavy Industries — widely used in copper, gold and iron ore operations
Outotec (Legacy)
Legacy Outotec SAG mill designs — various diameters up to 12.2m
Now Metso Outotec — original patterns and drawings maintained for legacy mills
Others
Svedala, Dominion, Hardinge, KHD, Marcy, Denver, Allis-Chalmers
Contact ATF with mill nameplate data for liner fit confirmation
Don't see your SAG mill manufacturer? ATF maintains drawings and patterns for SAG mills from all major and legacy manufacturers. Send your mill nameplate data, drawings or liner dimensions for fit confirmation.
Verify Your MillPlanning a SAG Mill Reline?
Send your mill specifications, current liner configuration and reline schedule for a comprehensive quotation. ATF can recommend alloy and profile optimisations — including bimetallic options and pebble port sizing — to extend liner life and improve grinding efficiency.
SAG Mill Liner Maintenance Best Practices
SAG mill relines are among the most expensive and time-critical maintenance events in a mining operation. Disciplined liner monitoring extends reline intervals, prevents unplanned downtime and maintains grinding circuit throughput. A worn lifter bar in a SAG mill changes the charge trajectory for hundreds of tonnes of material.
Every Shift
- Monitor mill power draw — sudden drops indicate liner failure, charge level changes or pebble port blinding
- Check mill bearing temperatures and lubrication pressure — SAG mill bearings carry extreme loads
- Listen for abnormal sounds: repeated metallic banging suggests a displaced liner or broken lifter bar
- Monitor pebble crusher feed rate — changes indicate grate pebble port condition
Weekly
- Sample and analyse product particle size — deviation indicates liner/lifter wear affecting charge trajectory
- Inspect trommel screen condition — torn or blinded screens reduce classification efficiency
- Check feed and discharge trunnion liners for wear or slurry flow restrictions
- Review pebble port throughput data for signs of blinding or enlargement
Monthly
- Measure shell liner thickness at multiple points using ultrasonic gauges — map the circumferential and axial wear pattern
- Inspect lifter bar heights across the full mill length — worn lifters change the charge trajectory and reduce impact energy
- Check accessible mill bolt tension — SAG mill vibration and thermal cycling loosen fasteners
- Inspect grate panels through access ports for cracking, wear-through or pebble port enlargement
At Liner Change (Reline)
- Inspect the mill shell for erosion, cracking or corrosion under the liner plates — especially around bolt holes
- Check all grate panels — replace any with worn, cracked or enlarged apertures or pebble ports
- Verify lifter bar heights and face angles meet the original design specification for your charge trajectory
- Inspect pulp lifter channels for blockage, wear-through or corrosion
- Replace all mill bolts — never reuse stretched or corroded fasteners in a high-energy SAG mill
- Inspect trunnion liner condition — trunnion damage from liner failure is extremely expensive to repair
Typical SAG Mill Operating Parameters
| Parameter | Standard SAG | High-Aspect SAG |
|---|---|---|
| Mill Diameter | 6.1–9.8 m (20–32 ft) | 9.8–12.2 m (32–40 ft) |
| Mill Speed | 72–76% critical | 70–74% critical |
| Ball Charge | 10–15% fill | 8–12% fill |
| Total Charge | 25–35% fill | 25–30% fill |
| Ball Size | 100–125 mm | 125 mm |
| Lifter Height | 200–300 mm | 250–350 mm |
| Liner Alloy | Cr-Mo (400–450 BHN) | Cr-Mo / Bimetallic |
Parameters are indicative. Optimal settings depend on mill dimensions, ore characteristics, ball charge strategy and grinding circuit design. High-aspect ratio SAG mills (D/L > 2) operate differently from conventional SAG mills. Always consult your process engineer for site-specific recommendations.
Common SAG Mill Problems & Solutions
SAG mill liner issues have immediate and significant impact on grinding circuit throughput. Recognising wear patterns and operational symptoms early prevents loss of production, unplanned reline events and damage to the mill shell. Contact ATF technical support if you need help diagnosing a SAG mill issue.
Coarser Product / Loss of Grinding Efficiency
Probable Causes
- Lifter bars worn below effective height — charge not being cataracted to the correct impact zone
- Shell liners worn smooth — lost high-lift profile reduces the charge lifting action
- Grate apertures blinded by near-size material, tramp metal or peg-leg balls
- Pebble ports blinded — critical-size pebbles accumulating in the charge instead of being extracted
Corrective Actions
- Measure lifter bar heights and compare to original specification — replace if below minimum effective height
- Inspect shell liner profiles — worn-smooth liners lose grinding effectiveness regardless of remaining thickness
- Clean and inspect grate panels — replace any with blinded, enlarged or cracked apertures
- Verify pebble port condition and pebble crusher circuit operation — clear any blockages
Liner Cracking or Breakage
Probable Causes
- Impact energy exceeding alloy toughness — oversized ore or excessive ball size for the liner grade
- Mill bolt failure allowing liner movement — cyclic loading fatigue-cracks unsupported plates
- Thermal stress from startup/shutdown temperature differentials in the heavy liner castings
- Incorrect liner profile creating point-load impact instead of distributed charge contact
Corrective Actions
- Review alloy selection — chrome-moly steel (400+ BHN) for SAG mill impact zones, bimetallic only in the lower shell
- Check and re-torque all mill bolts — replace any showing elongation, thread damage or corrosion
- Implement gradual mill speed ramp-up during startup to reduce thermal shock to liner castings
- Review liner profile geometry against the recommended design for your mill size and charge trajectory
Excessive Mill Vibration
Probable Causes
- Displaced or broken liner plate creating an imbalanced rotating mass
- Uneven charge distribution — material segregation or preferential loading from the feed arrangement
- Worn trunnion bearings or mill alignment shift — SAG mill mass amplifies any imbalance
Corrective Actions
- Stop and inspect mill interior for displaced liners — in a SAG mill, a displaced liner can cause cascading failure of adjacent plates
- Review feed distribution and charge level — ensure correct fill level (25–35%) and ball-to-ore ratio
- Check trunnion bearing clearances and mill alignment — resurface or replace as required
Reduced Mill Throughput
Probable Causes
- Grate panels partially blinded — restricting slurry and pebble discharge, causing the mill to pool
- Pulp lifter channels blocked with oversized media, broken liner fragments or tramp material
- Critical-size pebble accumulation — pebbles too large to grind and too small to cataract effectively
Corrective Actions
- Inspect and clean grate panels — replace any with worn or blinded apertures or pebble ports
- Clear pulp lifter channels and inspect for structural damage or wear-through
- Review pebble port sizing and pebble crusher circuit — ensure critical-size pebbles are being extracted and recirculated
Excessive Liner Wear Rate
Probable Causes
- Liner alloy not matched to ore abrasiveness and impact energy — too soft for the application
- Mill speed too high — excessive cataracting impact accelerates liner face wear
- Ball charge too high — excess steel media creates more steel-on-liner impact than designed
- Feed top size too large — oversized ore lumps concentrate impact energy on individual liner plates
Corrective Actions
- Review liner alloy against ore abrasion index (Ai) and Bond work index (Wi) — consider bimetallic for high-wear zones
- Verify mill speed as percentage of critical speed — adjust if outside recommended range (70–78% typical for SAG)
- Review ball charge volume and ball size distribution — typically 8–15% ball charge for SAG mills
- Check feed top size control — oversized feed should be screened or scalped before the mill
Frequently Asked Questions
Answers to common questions about SAG mill liners, material selection, pebble port design, maintenance and ordering. Can't find what you're looking for?
Contact Our TeamWhat is the difference between a SAG mill and a ball mill?
Why are SAG mill liners so much heavier than ball mill liners?
What are pebble ports and why do SAG mills need them?
How do I choose between chrome-moly and bimetallic SAG mill liners?
How often should SAG mill liners be replaced?
What information does ATF need to quote SAG mill parts?
Are ATF SAG mill parts compatible with OEM equipment?
What is the typical lead time for SAG mill parts?
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