Cement Clinker Transfer Conveyor for Greenfield Cement Plant in Rajasthan
Engineering Case Study
Case Study 2: Cement Clinker Transfer Conveyor for Greenfield Cement Plant in Rajasthan
Scenario
A new integrated cement plant near Chittorgarh, Rajasthan, required a short but critical 180 m transfer conveyor moving hot clinker (600°C surface temp) from the cooler discharge to the clinker silo. Environmental constraints were extreme: ambient temperatures regularly exceed 48°C, with high dust loading (>10 mg/m³) and zero tolerance for downtime due to kiln synchronization. The design had to accommodate thermal expansion of the belt and drive components while fitting within a tight 3.2 m vertical clearance envelope — ruling out gravity take-up systems and mandating a compact snub pulley arrangement.
Given Data
- Mass flow rate: 820 tonnes/hour
- Belt speed: 1.6 m/s
- Idler spacing: 1.0 m (reduced spacing for hot, abrasive clinker)
- Coefficient of friction: 0.028 (elevated due to fine dust infiltration into idler bearings and high-temp belt compound)
- Incline angle: −3.2° (decline — energy recovery opportunity considered but rejected due to safety and control complexity)
- Height difference: −10.0 m (confirmed via site topo survey)
Calculation
-
Horizontal resistance power: ( W_m = \frac{820}{3.6} = 227.8 , \text{kg/s} ), ( v = 1.6 , \text{m/s} ), ( C_f = 0.028 ) → ( P_h = \frac{0.028 \cdot 227.8 \cdot 1.6}{1000} = 10.2 , \text{kW} )
-
Decline (regenerative) power component: Since height difference is negative, this reduces required power: ( P_i = \frac{227.8 \cdot 9.81 \cdot (-10.0)}{1000} = -22.3 , \text{kW} )
-
Total power required: ( P_{\text{total}} = P_h + P_i = 10.2 + (-22.3) = -12.1 , \text{kW} ) → interpreted as net power assist needed. However, due to safety-critical braking requirements, full motoring capacity must still be provided to control descent speed and handle belt slippage or jam scenarios. Per ISO 5048 and plant SOP, the decline case requires sizing for absolute value of incline power plus horizontal losses plus 25% brake reserve margin. → Conservative total = ( |P_i| + P_h + 0.25 \cdot |P_i| = 22.3 + 10.2 + 5.6 = 38.1 , \text{kW} )
-
Recommended motor size: Apply 1.3 service factor (for high-temp, dusty, safety-critical duty per IEC 60034-1 Annex D): ( 38.1 \times 1.3 = 49.5 , \text{kW} ) → next standard size: 55 kW (IE3, 6-pole for lower speed/torque profile, IP66, high-temp insulation class H)
Result and Decision
A 55 kW, class-H insulated, IP66-rated motor with integrated electromagnetic fail-safe brake was commissioned. Field testing confirmed stable 1.58–1.62 m/s operation across ambient 35–48°C, with peak motor winding temps staying below 145°C. The brake engagement logic prevented uncontrolled acceleration during power loss — satisfying both process safety and regulatory audit requirements.
Lesson
In decline applications, never rely on theoretical power reduction alone — safety-critical conveyors require motor sizing based on worst-case motoring demand, including braking reserve, thermal derating, and failure-mode response — not just steady-state energy balance.