Electricity + Control January 2019

DRIVES + MOTORS + SWITCHGEAR

Wessels Mine cable belt conveyor upgrade

John Proctor, Siemens

Siemens, in partnership withTech Edge, is in the process of upgrading the cable belt conveyor at Wessels Mine in the Northern Cape. Wessels Mine hauls manganese ore from the underground crushing plant to the surface using the cable belt convey- or. The existing system was installed in 1979 and, to maintain reliability, the mine de- cided to upgrade the entire drive train (drive wheels, gearboxes, motors and drives).

1. In December 2017, South32 placed the or- der for the upgrade of the cable belt conveyor drive train. 2. The drive wheel and idler wheel dimensions have been matched exactly. Take Note! 1

Introduction In December 2017, South32, the owners of Wes- sels Mine, placed an order with Siemens for the upgrade of the cable belt conveyor drive train. The aim of the project was to extend the life of the cable belt for another 25 years. The existing con- veyor infrastructure will remain unchanged while the drive wheels, gearboxes, motors and drives will be upgraded. After multiple discussions with the customer, it was decided to extend the scope of the project to include a new MCC and 3.3 kV switchgear. Siemens has completed the factory accept- ance testing and when civil works are completed in early 2019, the company will able to complete the implementation. What is a cable belt conveyor? A cable belt conveyor has two steel cables that support the conveyor rubber belt. These steel ca- bles are driven by drive wheels and not the con- veyor belt itself as per standard conveyors. The rubber belt is folded over at the tip point and re- turns on the bottom ropes back down the mine. It is possible to have multiple conveyor flights using the same steel cables. The rubber belt has two pairs of grooves; the bottom grooves support the rubber belt and ore extracted out of the mine, the top grooves are used for the return trip back un- derground. Existing system The existing system uses a limited slip differential gearbox (see Figure 1 ) to achieve speed matching between the two steel cables. The cable belt is driv-

en by two 710 kW motors started Direct on Line (DOL) with fluid couplings and stopped by four hy- draulic brakes on each side.There is an idler wheel in front of the drive wheels (see Figure 2 ) to increase the wrap angle of the cable over the drive wheel.

Basic information on the cable belt conveyor

Cable belt information Item No Description Quantity Unit 1 Installed Aug-79 2 Total length 1675 m 3 Conveyor sys- tem length 3316 m 4 No. of conveyor flights 2 5 Angle 14.5 degrees 6 Vertical lift 392 m 7 Capacity 880 MT/h 8 Load design 84.2 Kg/m 9 Belt speed 3.3 m/s 10 Drive wheel size 3300 mm 11 Drive wheel rope wrap angle 230 degrees 12 Rope diameter 45 mm

Figure 1: Limited slip differential gearbox.

Existing system

13

Motor - voltage (two motors) Motor - power Motor - speed

3.3

kV

14 15

709 988

kW

Figure 2: Existing drive and idler wheels.

rpm

14 Electricity + Control

JANUARY 2019