Why Belt Scraper Selection Matters
Belt scrapers (belt cleaners) remove material that would otherwise stick to the belt underside and carry back along the return run. Carryback causes material buildup on return rollers, belt mistracking, belt underside wear, and continuous spillage under the conveyor. A properly selected and maintained scraper system eliminates these problems. A poorly selected or maintained system causes as many problems as it solves.
Primary vs Secondary Scrapers
| Scraper Type | Position | Removal Efficiency | Blade Material |
|---|---|---|---|
| Primary (head pulley) | Pressed against belt at head pulley | 70β?5% | Tungsten carbide or PU 70A |
| Secondary (return strand) | 1β?m after head pulley on return | Additional 10β?2% | PU 60β?0 Shore A |
| Tertiary (pre-tail) | Before tail pulley | Remaining fines | Rubber or PU |
| V-plow (diagonal) | Return strand, before tail | Spillage from return | Rubber |
Blade Material Selection
Tungsten Carbide Tipped Blades
Best for: abrasive ore (iron ore, copper, granite), high-speed conveyors, applications where maximum cleaning efficiency is needed.
- Hardness: ~1500 HV β?resists abrasive wear far longer than rubber or PU
- Service life: 6β?8 months on abrasive ore vs 1β? months for rubber
- Cost: 3β?Γ more than PU blades β?justified by extended life
- Risk: can damage belt if spring tension too high or belt has cover damage
Polyurethane (PU) Blades
Best for: coal, soft mineral ores, applications where belt surface protection is priority.
- Hardness: 60β?5 Shore A for primary scrapers
- Gentler on belt cover than tungsten carbide
- Self-conforming to belt surface β?good contact even with slight belt surface variations
- Service life: 3β? months depending on material abrasiveness
Spring Tension Setting
Scraper blade contact force must be in the correct range β?too low and the blade does not clean effectively; too high and the blade wears rapidly and can damage the belt:
- Primary tungsten carbide blade: 3β? N/mm blade width
- Primary PU blade: 5β?2 N/mm blade width
- Secondary PU blade: 3β? N/mm blade width
- Check and re-set spring tension monthly
When to Replace Scraper Blades
Replace blades when they have worn to 50% of original thickness β?not when completely worn out. A blade worn to the holder has zero cleaning effectiveness and the holder itself can damage the belt. Monthly blade thickness measurement is the best practice.
β?Complete Scraper System for Mining
For a mining conveyor handling ore: (1) tungsten carbide primary at head pulley, (2) PU 65A secondary 1.5m after head on return, (3) V-plow before tail pulley. This combination typically achieves 95β?9% carryback removal, eliminating the primary source of return run contamination and roller buildup.
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