Why Belt Tension Calculation Matters
Correct belt tension calculation determines: the minimum belt rating (breaking strength) required, the required drive motor power, and the take-up system design. Undersized belt results in splice failure; oversized belt wastes capital cost. This guide covers the simplified method for preliminary design.
Step 1: Calculate Effective Tension (Te)
Effective tension is the net force the drive must apply to the belt to move material at the required speed.
Te = Tf + Tl + Ts
Where:
- Tf = friction tension (resistance to belt and material movement)
- Tl = lift tension (gravity component on inclined conveyors)
- Ts = special resistances (skirtboard friction, scrapers, plows)
Step 2: Calculate Friction Tension (Tf)
Tf = f × L × g × (2 × mb + mm + mr)
Where: f = artificial friction factor (0.017—?.025 for well-maintained mine conveyors), L = conveyor length (m), g = 9.81 m/s², mb = belt mass per metre (kg/m), mm = material mass per metre (kg/m), mr = rotating mass of rollers per metre (kg/m)
Step 3: Calculate Lift Tension (Tl)
For inclined conveyors:
Tl = mm × L × g × sin(θ)
Where θ = conveyor inclination angle. For horizontal conveyors, Tl = 0.
Step 4: Calculate Required Belt Rating
The belt must have a breaking strength sufficient to carry the maximum tension in the belt:
T_max = Te × Cw / (1 - e^(-μα)) (Euler drive equation)
For simplified calculation, T_max —?1.3—?.5 × Te for typical drive arrangements.
Required belt rating (N/mm) = T_max / belt width (m) × safety factor (1.5—?.0)
Worked Example
| Parameter | Value |
|---|---|
| Conveyor length | 500m horizontal |
| Capacity | 1,000 t/h coal |
| Belt width | 1,000mm |
| Belt speed | 2.5 m/s |
| Belt mass | 18 kg/m (EP315/3, 6+3mm covers) |
| Material mass/m | Q/(3.6×v) = 1000/(3.6×2.5) = 111 kg/m |
| Roller mass/m | ~15 kg/m (estimate) |
| Friction factor f | 0.020 |
| Effective tension Te | 0.020 × 500 × 9.81 × (36+111+15) = 159 kN |
| Drive power | Te × v = 159 × 2.5 = 398 kW —?select 400 kW motor |
| T_max (approx) | 1.4 × 159 = 223 kN |
| Required belt rating | 223,000 / 1.0m / 1.5 SF = 149 kN/m —?select EP200 |
—?Simplified Belt Rating Selection
For preliminary design without full calculation: Required belt rating (N/mm) —?2 × drive power (kW) / belt speed (m/s) / belt width (m). For the example above: 2 × 400 / 2.5 / 1.0 = 320 N/mm —?EP315 is appropriate.
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