India's first Elevated, Triangulated Gallery Overland Conveyor System

Overland Conveyor System

India's first Elevated, Triangulated Gallery Overland Conveyor System

In 2010 the Adani Group broke ground on a new solid cargo handing port with the installation of a unique conveyor system that moves up to 6000 t/h to a rail loading silo approx. 4.75 kilometres from the port. These conveyors are supported by lightweight triangular galleries that do not include walkways and are maintained with a motorised trolley.
(ed. WoMaMarcel - 17/7/2014)
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System Overview

The Silo Conveyor system is comprised of three conveyors connected in series that transport up to 6000 t/h of coal from the Dahej port to a rail wagon loading silo.

The first conveyor in the series is SC-1A (Silo Conveyor 1A). SC-1A is 1.6 km long and gains 6.7 m of elevation. It transports up to 6000 t/h on an ST1000 1600 mm wide belt traveling 7.5 m/s. Two horizontal curves with 1100 m radii and nine vertical curves with various radii are included in the conveyor route. Most of the conveyor is located in an elevated gallery that is 6 m above the ground except where the conveyor crosses roads. Here the gallery elevation rises to 9 m above the road grade. SC-1A is powered by two 500 kW invertor driven motors, and includes two brakes. One brake is located on the tail pulley, and the other is located within the take-up sheave assembly. This second brake is used to boost the take-up tension during an unpowered stop.

SC-1A discharges onto the second conveyor in the series tagged SC-2A. SC-2A is 1.4 km long and gain 8.7 m of elevation. It transports up to 6000 t/h on an ST1000 1600 mm wide belt traveling 7.5 m/s. Like SC-1A the entire conveyor is elevated at least 6m off the ground. It is powered by two 500 kW invertor driven motors.

Currently, SC-2A directs feed onto a 485 m long low speed conveyor tagged SC-3. However, SC-2A’s discharge chute includes a diverter gate that will allow SC-2A to discharge coal onto the Adani Power Conveyor system in the future. SC-3 discharges coal into the rail wagon loading silo.

Route Optimisation

The route selected for the silo conveyors was tightly constrained by a number of existing industries occupying most of the land outside the port, by Lakhigam village, and by a large road. The conveyors could not pass outside a 5 m wide corridor between the road and surrounding developed properties. CDI was able to eliminate two transfer houses that were in the original feasibility study using tight 1100 m radius horizontal curves. However, we could not design a conventional conveyor with a curve tight enough to avoid a transfer station outside Lakhigam village. The final route is shown in Fig. 2.

Engineering horizontal curves like the two in this system is an iterative process. First, a rough profile of the conveyor is selected. The tensions along the conveyor route are computed and used to determine the minimum horizontal curve radius that the conveyor can safely negotiate. The tension prediction must be accurate and requires drag prediction using rubber rheological equations [1] and dynamic analysis [2]. After determining the belt tensions, a new route is selected with horizontal curves and tensions for the new route are computed. The process is then repeated.

Unusual Features of SC-1A

SC-1A is designed with a number of unusual features including:

  • High Speed: Only one other conveying system in India runs as fast as Dahej-- the Mundra Port overland system, a collaborative design effort between CDI and Elecon.
  • Lightweight: The triangular galleries that support SC-1A weigh only 209 kg/m and span 36 m apiece. This is half the weight and 50% more span than the typical box style conveyor gallery.
  • Motorised Maintenance Trolley: To save weight, the triangular gallery does not include walkways. Workers maintain the system using a motorised trolley.
  • Horizontal Curves: the 1100 m radius horizontal curves are among the tightest radius horizontal curves in the world for 1600 m wide conventional steel cord troughed conveyors.
  • Low Dust: an integrated low profile stringer-hood completely encloses the coal removing the need for side cladding on the gallery to prevent the release of dust into the environment.
  • Low Rolling Resistance Belt: The bottom cover of the Dahej conveyor uses a low rolling resistance rubber compound that provide substantial power savings over the lifetime of the system.
  • Low TIR idlers: All idlers installed on this system had a TIR of less than 0.4 mm. This reduced the friction and noise generated by the conveyor.

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