The major order with a total volume of 5 million Euros includes development and installation of a 12.5 kilometre long installation through rough mountainous terrain. The Asia Cement Group, a major building material manufacturer headquartered in Taipei (Taiwan), has built a new plant in the vicinity of Chengdu, the capital of Sichuan.
Currently, a furnace chain with a capacity of 4,200 tons per day is installed there. For moving the limestone from the quarry to the factory, located 30 km away, the Asia Cement Group has commissioned BEUMER Group with building a curving troughed belt conveyor installation.
Logistical and engineering challenge
For more than 20 years the Asia Cement Group has worked with BEUMER Group and has numerous installations and bucket elevators by the machine-manufacturing company in operation. Due to the conditions of topography and the resulting logistical and engineering requirements, development, bridging and commissioning of the conveyor had to come from one source.
In May 2006 the Asia Cement Group placed the order for the 12.5 kilometre long troughed belt conveyor with a mass flow of 1,500 tons per hour and a conveying speed of four metres a second with the BEUMER Group.
The terrain to be conquered consists of mountains and bamboo forests. Since a good portion of the bamboo is under nature conservation, no approval was given for a service route, nor was any clear cutting allowed. Even the subsoil posed a serious challenge for BEUMER Group engineers: for one thing, the ground is unstable because of previous coal mining.
At other points the ground consists of granite that can only be removed to a certain extent. In addition, along the route a segment has to be routed through 1.5 kilometres of water. Such extreme outer constraints entail having to mount manually about 90 percent of the installation on site.
Since transport by lorry is to some extent impossible the structures have to be carried by mules, piece by piece. For that reason BEUMER Group designed the entire facility in such a way that all parts can be screwed on and have a carrier length of only three metres. In that way optimum transport can be ensured.
Altitude differences of up to 100 metres
After the order was placed, the BEUMER Group in consultation with the Asia Cement Group optimised the routing of the troughed belt conveyor on the spot. With eight horizontal curves having a radius of some 1,000 to 5,000 metres, the machine manufacturer calculated the precise belt tensile forces in costly simulations.
Besides rough terrain, extreme altitude differences of up to 100 metres posed a particular challenge. In order to minimise total costs as much as possible, BEUMER Group has used four horizontal curves and spans the mountains with bridges up to 55 metres in height.
Coping with any challenge
For the 12.5 kilometre long conveyor installation the length of the belt is 25 kilometres. The belt has to be vulcanised in 56 places. The width of the belt is 1,200 mm and its rigidity is 2,800 N/mm. Besides the eight horizontal curves the installation has 28 vertical curves. In order to keep belt tensile forces under control through six declining segments and six inclining ones the installation is operated with special motors and with BEUMER controls adapted to them.
The installed driving power comes to six times 500 kW, frequency regulated with BEUMER controls. Driving power is divided into two drive pulleys at the installation's feed and head, respectively. In this case, one pulley acts as a double drive for 1000 kW and one as a simple drive for 500 kW. A movable take-up weight was dispensed with and instead the take-up weight is adjusted once and geometrically frozen with a take-up winch.
The troughed belt conveyor should be installed and in operation by mid 2008. Despite all logistical and topographic obstacles the BEUMER Group has coped with every challenge and is right on schedule with construction.
