Belt Conveyor Tension & Power Calculation | DGMS Mechanical Notes
🔹 1. Introduction
Belt conveyors in mines operate under continuous load, requiring accurate tension and power calculations to ensure reliability, safety, and efficiency. Improper tension leads to belt slippage, excessive wear, misalignment, or breakage, which can cause accidents and production loss.DGMS (Directorate General of Mines Safety) mandates that conveyor systems must be designed, inspected, and maintained as per CMR 2017 Regulation 88 & 131, ensuring correct tensioning systems and safe operation.
🔹 2. Types of Belt Tension
A conveyor experiences several types of tension:A. Tight-Side Tension (T₁)The higher tension side of the belt loop during operation.B. Slack-Side Tension (T₂)Lower tension side that must meet minimum friction requirement.C. Effective Tension (Te)The tension needed to move the belt and material.Te=T1−T2Te = T₁ - T₂Te=T1 −T2D. Tension due to Material Lift (Tₕ)For inclined conveyors:Th=ρQgHTₕ = ρQgHTh =ρQgHE. Tension due to Belt Weight (Tb)Significant in long conveyors.F. Starting Tension (Ts)Starting loads are 1.5–2.5 times running loads.G. Centrifugal Tension (Tc)Important when belt speeds exceed 10 m/s.
For friction drive:T1T2=eμθ\frac{T₁}{T₂} = e^{μθ}T2 T1 =eμθWhere:
μ = friction coefficient (0.3–0.35 typical)
θ = wrap angle (in radians)
Larger wrap = better grip = reduced slippage.
🔹6. Pulley Diameter & Belt Strength
Bigger belt thickness requires bigger pulley diameter to avoid bending failures.DGMS Safety Factor:
Fabric belts → ≥ 8
Steel-cord belts → ≥ 10
🔹7. Example Tension CalculationGiven:
Belt load = 1000 kg
Lift = 12 m
Belt speed = 3 m/s
Effective tension = 5000 N
Power:P=Te×v=5000×3=15000W=15kWP = Te \times v = 5000 \times 3 = 15000 W = 15 kWP=Te×v=5000×3=15000W=15kW
🔹 8. DGMS Guidelines for Tension & Power Design
✔ Tension must be within safe working limits ✔ Backstop must be fitted on inclined conveyors ✔ Weekly inspection of take-up, idler friction, slippage ✔ Belts must not slip under rated tension ✔ Overload protection & interlocking mandatory
🧠9. 25 DGMS-Style MCQs with 5 Options
1) Effective tension (Te) is —
a) T₁ + T₂ b) T₁ − T₂ c) T₁ × T₂ d) T₁ / T₂ e) None ✅ Answer: b Explanation: Te = T₁ − T₂ (difference between tight-side and slack-side tension). 2) Power for a conveyor is calculated using —
a) P = T / r b) P = Te × v c) P = Q × ρ d) P = D × N e) None ✅ Answer: b 3) Tension ratio T₁/T₂ is given by —
a) μθ b) e^(μθ) c) μ + θ d) μ − θ e) None ✅ Answer: b 4) Typical friction coefficient (rubber–steel) is —
a) 0.05 b) 0.10 c) 0.20 d) 0.30–0.35 e) 0.70 ✅ Answer: d 5) Wrap angle in tension formula is expressed in —
a) Degrees b) Radians c) Percentage d) Newtons e) None ✅ Answer: b 6) Maximum belt tension occurs at —
a) Tail pulley b) Head pulley c) Return idler d) Loading point e) Drive guard ✅ Answer: b 7) Tension on return run is generally —
a) High b) Low c) Equal to T₁ d) Zero e) Infinite ✅ Answer: b 8) Lift tension (Th) equals —
a) Q × H b) 2H / Q c) ρQgH d) H × v e) 1/H ✅ Answer: c 9) Starting factor (Ks) generally lies between —a) 1 b) 1.2 c) 1.5–2.5 d) 5 e) 10 ✅ Answer: c 10) Minimum slack tension (T₂) is required to prevent —
a) Vibration b) Slippage c) Belt sway d) Noise e) Sag ✅ Answer: b 11) Effective tension is increased by —
a) Lowering friction b) Reducing inclination c) Removing load d) Increasing load resistance e) Belt lubrication ✅ Answer: d 12) Belt power increases when —
a) Belt speed decreases b) Inclination decreases c) Load reduces d) Tension increases e) None ✅ Answer: d 13) Belt tension due to belt weight is significant in —
a) Short conveyors b) Small conveyors c) Long conveyors d) Curved conveyors e) Declines only ✅ Answer: c 14) Pulley diameter increases with —
a) Belt speed b) Idler spacing c) Load d) Belt thickness e) Slope ✅ Answer: d 15) Working tension for steel-cord belts is about —
a) 5% of breaking strength b) 10% of breaking strength c) 20% d) 30% e) 40% ✅ Answer: b 16) Largest tension component in long conveyors is —
a) Belt weight b) Material lift c) Load friction d) Idler rolling resistance e) Air drag ✅ Answer: d 17) Slack-side tension T₂ is determined by —
a) Belt width b) Idler spacing c) Motor RPM d) Minimum friction requirement (no-slip) e) Belt color ✅ Answer: d 18) Power requirement decreases when —
a) Belt speed increases b) Load increases c) Inclination increases d) Idler friction decreases e) Material density increases ✅ Answer: d 19) T₁ refers to —
a) Return run tension b) Tight-side tension c) Take-up tension d) Gravity tension e) None ✅ Answer: b 20) T₂ refers to —
a) Tight side b) Slack side c) Dynamic tension d) Impact tension e) Brake tension ✅ Answer: b 21) Power requirement increases with —
a) Higher inclination b) Higher load c) Higher speed d) All of these e) None ✅ Answer: d 22) Centrifugal tension becomes significant above —
a) 1 m/s b) 3 m/s c) 5 m/s d) 10 m/s e) 15 m/s ✅ Answer: d 23) Weak belt splicing leads to —
a) Longer life b) Better tension distribution c) Premature belt failure d) Higher capacity e) Faster speed ✅ Answer: c 24) Over-tensioning results in —
a) Less wear b) Better capacity c) Uniform running d) Belt tear and pulley damage e) Lower friction ✅ Answer: d 25) DGMS tension safety factor for fabric belts is —
a) 2 b) 4 c) 6 d) 8 e) 12 ✅ Answer: d
🔚 10. Conclusion
Accurate tension and power calculations ensure safe, efficient, and reliable belt conveyor operation. Correct tensioning prevents slippage, spillage, overheating, belt failure, and enhances motor performance.DGMS mandates regular monitoring of tension components to maintain zero-slip, zero-rollback, and zero-accident operations.
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