Replacing the Conveyor Belt of a Long Distance Pipe Conveyor at the Skyline Mine

The initially installed pipe conveyor belt St1000 (1000 Newton per millimetre), 1600 millimetres width, covers 9 millimetres + 6 millimetres had a layer of transverse fabric reinforcement (breaker) above and below the steel cables, which were separated by a rubber layer from the steel cords [1]. Such design is very beneficial in keeping the overlap in the 12-o’clock-position and provides good belt guidance in curves. Nevertheless, because of the large number of sharp horizontal and vertical curves and based on the experience with the initially installed pipe conveyor belt of a third party manufacturer, Contitech designed a new pipe conveyor belt. The new belt utilised a combination of fabric and steel transverse reinforcements: Rollgurt 1000 S-K2, 8T:6S, 1600 millimetres width, Contiextra with a nominal breaking strength of k_N = 1000 Newton per milliemetre.

Special attention was given to the design of edge areas of the new pipe conveyor belt and to the correct selection of the rubber compound. The new design allows a safe operation at a min. curve radius R_min = 365 metres (1200 feet) and a more stable tubular shape, so the possibility that the belt can collapse in the future is greatly reduced. The selected rubber compound Contiextra works at the temperature of T = -40 °C (-40 °F) even with strong deformations resulting from the conveyor profile and the pipe forming.

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The final tests, including analysing and establishing the forming forces, confirmation of the tubular shape and form of overlap, and defining the behaviour of the pipe belt sample in a curve at the temperature range of +38 °C (+100 °F) to -40 °C (-40 °F), were conducted at Contitech test facilities in Northeim, Germany.

The considerations, as stated above, show that the most important parameter is a sufficient contact length and contact force between the belt and the idlers, in order to guide the belt through a curved conveyor. This can only be achieved by a belt design with optimised transversal stiffness and flexibility. Hence, it is evident that a pipe conveyor belt is designed and specified in order to gain an optimised solution for the specific application cases with respect to tracking capabilities, as well as power demand.

Consequently, the design of a pipe conveyor and of a pipe conveyor belt is significantly different from the common design of a standard belt conveyor and of a belt that is used for troughed conveyor applications. That is why OEMs and belt manufacturers should work side by side to optimise the pipe conveyor in detail.

Pipe Conveyor Belt Replacement Procedure

When a new conveyor belt has to be installed as a retrofit, upgrade or replacement of an existing transport method, the impact of the conveyor system downtime and the resultant lost production should be minimised. After analysing the terrain and routing and in consultation with the customer, Contitech decided to pre-splice and pull in the new belt from behind of the BC-8 head station. Similar to the KPC-project [3], the new pipe belt was connected to the existing old belt via a temporary (dummy) splice. As the new belt was pulled into the system, the old belt was pulled out. This temporary splice, however, needs to be a 100-percent-functional splice for the occasions when the system needs to be restarted at normal operating parameters, before the belt replacement is completed. Fig. 7 shows the principle of reeving the belt prior to the belt pulling. The access to the idler frames and the pipe conveyor belt was very limited because the conveyor system is mainly installed in fully covered trusses and galleries.

The belt was shipped in eight reels, a total of 6940 metres. The pipe belt was pulled from the belt reel through the splice shed and reefed in approx. 75 layers, resulting in a belt stack of approx. 1.5 metres height (Figs. 8 and 9). In order to reduce friction forces between the layers while reeving and pulling the belt, each belt layer was separated by a layer of sand. Reeve tubes were installed to protect the belt from a sharp bend where the belt folded back on itself (Fig. 10). For this pipe belt, a special splice design was used that differs dramatically from designs for standard troughed belts. Before starting to pull in the new pipe belt, Contitech estimated resistances to motion and checked if the installed total drive power was sufficient to pull the final section of the new pipe belt onto the system. Figs. 11, 12 and 13 give an overview of the setup for the belt pulling into the conveyor system.

At creep speed and using the installed DC-drives, the old belt was pulled out while the new belt was fed into the return strand of the pipe conveyor structure from the stack of reeved belting. In order to access the head pulley of the conveying system a lift of approx. 12 metres (39 feet), consisting of inaccessible terrain, was negotiated from the laydown area to the head end. A temporary conveyor of approx. 52 metres (170 feet) in length was installed (Figs. 11, 12 and 13) to reduce friction and to guide the new belt towards the feeding point.

With this setup, the belt was installed quite smoothly within five days. The old belt was spooled on a reel by a powered winder. After the pulling was completed, the belt was closed to form an endless belt with the final splice.

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