Background
A coal-fired power station in QuαΊ£ng Ninh Province, Vietnam was expanding its coal handling capacity. The expansion included a new coal unloading conveyor from the river barge dock to the coal stockpile, and a reclaim conveyor from the stockpile to the crusher house. The station burned approximately 3,000 tonnes of coal per day.
The project engineer requested belt specifications for both conveyors:
- C1 (Barge unloader to stockpile): 1,200mm wide, 620 meters long, 15-meter net lift, 1,500 t/h design capacity, 2.5 m/s belt speed
- C2 (Reclaim to crusher): 1,000mm wide, 280 meters long, flat, 1,200 t/h, 2.5 m/s
Coal Characteristics and Environment
The coal was imported thermal coal from Kalimantan, Indonesia β a sub-bituminous coal with relatively low abrasion index. Moisture content at delivery was 15β25%. The site was adjacent to a river in a humid coastal environment with high year-round rainfall.
Key environmental factors: - Outdoor conveyors fully exposed to year-round tropical rainfall - High humidity and salt air from proximity to the coast - The coal occasionally arrived with higher-than-normal moisture content during wet season
Belt Specification
C1 β Barge Unloader to Stockpile:
Tension calculation for 620m with 15m lift at 1,500 t/h gave maximum belt tension of approximately 165 kN/m. With safety factor of 7: minimum break strength required = 1,155 N/mm.
Options: EP500 (500 kN/m β insufficient), EP630 (630 kN/m β borderline), or ST1250 (steel cord).
Given the outdoor long-distance application and the value of low elongation for the take-up system, ST1250 steel cord was specified.
- ST1250, 1,200mm wide
- Top cover: 8mm M24, tropical weatherproof (UV-stabilized, ozone-resistant)
- Bottom cover: 5mm M24
C2 β Reclaim to Crusher:
Tension calculation for 280m flat at 1,200 t/h gave maximum belt tension of approximately 85 kN/m. EP315 with safety factor of 7 gives 315 kN/m break strength β more than adequate.
- EP315, 1,000mm wide
- Top cover: 8mm M24, tropical weatherproof
- Bottom cover: 4mm M24
Covers for both: Ozone-resistant, UV-stabilized EPDM compound β standard specification for outdoor coastal Vietnam.
Wet Coal Considerations
High-moisture coal at 20β25% moisture content is one of the stickier materials to handle on a conveyor. The specification addressed this:
Scraper system: Primary + secondary scrapers on both conveyors, with polyurethane blades rather than tungsten carbide. PU blades release wet sticky coal more effectively than the harder tungsten carbide surface.
Return idlers: Rubber disc self-cleaning return idlers throughout C1 (the longer conveyor more prone to buildup on return idlers from wet coal). Standard steel return idlers on C2 (shorter, easier to clean manually if needed).
Loading chute design: The barge unloader discharge chute was rubber-lined and designed with smooth curved profile to reduce coal velocity at belt contact β reducing the tendency for wet coal to splash and spread at the loading point.
Outcome
Both conveyors commissioned and ran through the first wet season without unplanned belt-related stops. Carryback on C1 was managed by the scraper system β inspection at 3 months showed acceptable cleanliness.
The ST1250 on C1 was inspected at 18 months and showed minimal cover wear β the low abrasion of the coal and the good cover specification gave extended life projection. The EP315 on C2 was still in service at the same inspection.
Key Points
Power station coal is typically low-abrasion. Standard M24 cover is appropriate β no need for high-grade abrasion compounds. Focus instead on weatherproofing and wet-coal handling characteristics.
ST belt vs EP for longer conveyors is driven by tension and elongation, not abrasion. The ST1250 choice for C1 was purely a tension and take-up consideration, not an abrasion issue.
Scraper blade material for wet sticky coal: PU blades outperform tungsten carbide for wet coal release. This is a material-specific recommendation that differs from the general preference for tungsten carbide in most hard-rock mining applications.
Elephant Rubber supplied both conveyor belts for this project.