Background
A nickel laterite mining operation in Surigao del Norte, Philippines was specifying conveyor belts for a new crushing and screening facility handling direct shipping ore (DSO). The ore would be screened to remove oversize before being trucked to the port at Claver for export to Chinese smelters.
The conveyor system included: - A primary jaw crusher feed conveyor (C1): 650mm wide, 120 meters long - A vibrating screen feed conveyor (C2): 800mm wide, 85 meters long - Two screen undersize conveyors (C3/C4): 650mm wide, 60 meters each - An oversize return conveyor (C5): 500mm wide, 45 meters
The mine's engineering contractor requested belt specifications for all five conveyors.
Belt Selection Process
Material characteristics: Nickel laterite is a soft ore with low abrasion compared to sulfide ores or iron ore. The material is fine-grained and plastic when wet β it has a high clay content that makes it sticky and cohesive. Moisture content during mining typically ranges from 25β40%.
Key challenges identified: 1. Wet, sticky laterite adheres to belt covers β carryback is a significant issue 2. The ore is soft β abrasion resistance is less critical than material release 3. The Philippines has year-round high rainfall and humidity β cover compounds must resist ozone and mold 4. The loading point for C1 involves a 1.8m drop from the grizzly feeder β impact resistance matters here
Specifications selected:
| Conveyor | Width | EP Rating | Cover | Notes |
|---|---|---|---|---|
| C1 (crusher feed) | 650mm | EP200 | 8mm top M24, ozone-resistant | Impact zone at loading; thick top cover |
| C2 (screen feed) | 800mm | EP200 | 6mm top M24, ozone-resistant | Moderate load |
| C3/C4 (undersize) | 650mm | EP150 | 6mm top N17, ozone-resistant | Fine material, light load |
| C5 (oversize return) | 500mm | EP150 | 6mm top N17, ozone-resistant | Light duty |
N17 cover was appropriate for C3/C4 and C5 because the fine undersize material at low tonnage does not generate significant abrasion. M24 for C1 and C2 provides appropriate abrasion resistance for the coarser ore at higher tonnages.
Ozone-resistant compound was specified for all belts given the outdoor tropical environment. Standard SBR covers develop surface ozone cracking within months in the Philippine climate without ozone stabilizers.
Scraper and Skirt Specification
Given laterite's stickiness, the scraper system received particular attention:
- Primary and secondary scrapers specified for all loaded conveyors
- Polyurethane blades selected (better release of sticky material than tungsten carbide in this application)
- Skirt rubber: 50 Shore A (softer than standard to minimize belt cover scoring β laterite-impregnated skirting can act as an abrasive if too hard)
The engineering contractor was advised to install belt washing systems at the head end of C1 and C2 if carryback remained a problem after the initial operating period. Water wash systems are more effective than scrapers alone for extremely sticky wet laterite.
Outcome
The conveyor system commissioned and ran through the first wet season without belt-related stoppages. Carryback was present but manageable with the scraper system β within normal levels for laterite handling. The ozone-resistant covers showed no surface cracking at the 12-month inspection.
The belt washing system was not ultimately needed β the scraper system with PU blades proved adequate for this ore's stickiness level. The contractor noted this was better than expected based on experience with other laterite operations.
Key Points
Wet sticky ore calls for scraper attention at specification stage. Carryback from nickel laterite is predictable. Designing the scraper system properly from the start avoids retrofitting later.
Ozone-resistant covers are the baseline specification for outdoor tropical conveyors. This is not an upgrade β it's the correct specification. Standard SBR covers in outdoor Philippine conditions will crack within months.
Abrasion grade should match the actual ore. Laterite does not need DIN W or Z grade covers. M24 and N17 are appropriate. Over-specifying abrasion resistance adds cost without benefit.
Elephant Rubber supplied the conveyor belts for all five conveyors in this project.