1. Definition & Working Principle

Coal washer chain, also known as heavy medium shallow tank chain, is a heavy-duty engineering conveyor chain specially developed for coal preparation plants. It serves as the core traction component of shallow tank heavy medium separators and coal slime scraper conveyors. Driven by sprockets, the chain circulates continuously in heavy medium slurry to pull scrapers, realizing separation of clean coal and gangue as well as slag discharge.

2. Typical Working Conditions

The chain runs submerged in abrasive heavy medium slurry mixed with coal, rock particles and water. It bears combined loads including continuous tension, frequent impact from lump coal and gangue, abrasive wear and weak corrosion. Long-time cyclic operation requires excellent fatigue resistance.

3. Main Materials & Heat Treatment

• Base material: 40Cr, 42CrMo alloy steel; heavy-duty option: 23MnNiMoCr54
• Heat treatment: Pins and bushes adopt carburizing hardening or induction hardening. Chain plates go through quenching and tempering. Surface hardness reaches HRC 52~60 to balance wear resistance and impact toughness.
• Surface treatment: Blackening or anti-corrosion coating for protection against coal slime and medium water erosion.

4. Core Structure & Key Models

It features thickened chain plates and reinforced pins and bushes. Extended pins are reserved for mounting scraper flights. The most widely used model is P78.1, with a pitch of 78.1 mm. Custom pitches and attachments are available according to equipment drawings. Low permanent elongation is critical, which prevents chain slack and unstable meshing after long running hours.

5. Critical Performance Indicators

1. High breaking load to resist impact from large coal and gangue blocks
2. Superior slurry abrasion resistance
3. Resistance to moisture and weak medium corrosion
4. Low elongation and good fatigue performance for continuous 24h operation
5. Stable meshing performance with sprockets under wet conditions

6. Difference Between Coal Washer Chain & Underground Mining Scraper Chain

• Coal washer chain: Works in wet heavy medium slurry. Design priorities are slurry abrasion resistance and corrosion resistance.
• Underground AFC scraper chain: Works under dry dusty underground conditions. Design priorities are ultra-heavy impact resistance and explosion-proof related requirements.

7. Common Failure Modes

• Bush and pin wear: Caused by abrasive coal slurry, leading to chain elongation.
• Fatigue fracture: Caused by repeated impact and cyclic tension.
• Corrosion pitting: Generated by long contact with heavy medium solution.
• Scraper attachment failure from overload impact.

8. Maintenance & Service Tips

• Regularly check chain elongation. Replace the chain once elongation exceeds the allowable limit.
• Keep proper tension; avoid over-tightening or slack running.
• Inspect pins, bushes and scraper attachments for cracks or wear during plant shutdown.
• Clean accumulated coal slime to reduce abrasive wear.

9. Standards & Customization

Products can be manufactured complying with ISO, DIN and mining industry standards. Custom service covers pitch, chain width, scraper attachments and connecting links based on OEM drawings of coal washing machines.

Short Version for Website Introduction

Coal washer chain is heavy-duty traction chain for shallow tank heavy medium separators in coal preparation plants. Operating in coal and heavy medium slurry, it needs great wear resistance, impact toughness and anti-corrosion performance. Main material is 42CrMo alloy steel with professional heat treatment. P78.1 is the mainstream model. Custom attachments and sizes are acceptable.