Underground mining scraper conveyor applications represent some of the most demanding conditions that roller chain is required to survive — abrasive rock dust, coal fines, or ore particulate continuously contaminating the chain joints; shock loads from blast debris or oversize material; wet conditions from mine drainage; elevated temperature from geothermal gradient and equipment heat; and extreme consequences if a chain failure halts production.
Chain Type for Mining Scraper Conveyors
Most underground scraper conveyors use chain types specifically designed for mining and bulk material handling rather than standard ANSI roller chain. The three most common chain types in Australian underground mining scraper conveyors are:
| Chain Type | Typical Pitch | Tensile Strength | Best Application |
|---|---|---|---|
| Round link chain (Grade 80 or Grade 100) | Not applicable — round link chain has no fixed pitch in the roller chain sense | 300 to 800 kN per strand depending on wire diameter | Armoured face conveyors (AFCs) in longwall coal mining — highest strength-to-weight ratio for armoured conveyor scraper chains |
| Welded steel bushed chain (engineering class) | 100 to 200 mm pitch | 200 to 600 kN | Gate belt drives, drift conveyor chains, medium-duty scraper conveyors |
| Heavy duty ANSI or ISO roller chain (extra heavy series) | 25.40 to 50.80 mm pitch (ANSI 80 to ANSI 160) | 80 to 400 kN | Auxiliary mining conveyors, material handling conveyors, drive chain on belt conveyor head pulleys |
Key Specification Criteria for Underground Mining Chain
1. Contamination Resistance
Underground mining environments produce extremely abrasive fine particles — coal dust, rock flour, and ore fines — that penetrate chain joints at a rate far exceeding normal industrial environments. For standard roller chain used in auxiliary drive applications, O-ring roller chain prevents abrasive particles from entering the pin-bushing clearance and provides service life 3 to 5 times greater than standard non-sealed roller chain in coal mining environments.
2. Tensile Strength and Safety Factor
Mining scraper conveyors operate with safety factor requirements set by government and industry regulation. In Australian coal mining, the minimum safety factor for drive chain is typically 6:1 (chain breaking load to maximum working tension) — significantly higher than the 4:1 or 5:1 factor used in standard industrial drives. This additional safety factor must be applied on top of the standard service factor calculation for mining shock loading.
3. Shock Load Rating
Scraper conveyor chain must handle shock loads from oversize rock or coal entering the conveyor pan, scraper bar impacts on floor irregularities, blast-damaged conveyor sections, and emergency stop events. Apply the highest service factor (K₂ = 1.7 to 2.0 for very heavy shock loading) when calculating the design chain pull for underground mining conveyor chain.
4. Underground Environmental Requirements
Many underground mining environments — particularly coal mines — have strict requirements for chain materials and lubricants to prevent ignition risks. Lubricants used on underground coal mine chain must be fire-resistant or anti-static. Consult the relevant mine safety authority approved product list for the specific mine before specifying lubricants.
Lubrication for Underground Mining Chain
Automatic lubrication systems are strongly preferred for underground mining chain over manual lubrication for two reasons: manual lubrication is labour-intensive and difficult to perform consistently in confined underground spaces, and the high contamination rate of underground environments means the lubrication interval must be very frequent to maintain adequate film protection. Automatic lubricators that apply fire-resistant mineral or synthetic oil at every chain revolution provide the most effective protection in underground coal and metalliferous mining applications.
Chain Tension Monitoring in Underground Conveyors
Chain elongation monitoring in underground mining conveyors is more critical than in surface applications because chain replacement in underground environments is physically difficult and production-critical. Measure elongation every 500 to 1,000 operational hours and plot the elongation progression. Replace chain at 2 percent elongation (rather than the standard 3 percent threshold) in mining applications to provide a safety margin against unexpected rapid elongation from contamination events or shock overloads.
EverPower Roller Chains Australia can advise on heavy duty roller chain specification for underground mining and bulk material handling applications. Contact +61 2 9708 3322 or [email protected] with your conveyor specification details.
+61 2 9708 3322 | [email protected] | 27 Harley Crescent, Condell Park NSW 2201