Pipe Conveyor Technology Replacing the Conveyor Belt of a Long Distance Pipe Conveyor at the Skyline Mine
When the Arch Western Coal Skyline Mine decided to replace the old belt of its long distance BC-8 pipe conveyor, a new belt had to be designed to be suitable to the existing routing. In addition, a special installation procedure had to be developed to minimise downtime during the belt installation and commissioning.
When the Arch Western Coal Skyline Mine, located near Helper (UT), USA, decided to replace the belt of its pipe conveyor BC-8, it awarded the contract to design, manufacture, supply and replace the existing belt and commission the new belt to Contitech Conveyor Belt Group from Germany. A special challenge of the project was to design the new pipe steel belt to be suitable to the existing routing of BC-8, and to minimise the downtime due to belt installation and commissioning to reduce loss of production. During commissioning and after break-in, the company also carried out power measurements to asses the the energy efficiency of the new belt.
The Skyline Pipe Conveyor BC-8 is located approx. 3500 metres above sea level and transports 1270 tonnes of coal per hour over a distance of approx. 3400 metres downhill from the mine site to the mine’s train loading facilities. The pipe conveyor has 22 horizontal and 45 vertical “sharp” curves and an elevation drop of -172 metres.
Before Thyssenkrupp Robins (TKRI) was contracted to build the pipe conveyor, trucks were used to transport coal. Transporting coal by pipe conveyor significantly improved the efficiency for maintenance and operations by a factor of 9 when compared with trucking . The turnkey project included the design, delivery, installation and commissioning of the pipe conveyor belt.
Upon initial installation, the Skyline Mine Overland Pipe Conveyor BC-8 was the highest capacity and second longest steel belt cord pipe conveyor in the world. Since 1993, additional pipe conveyors that are longer and of higher capacity, have been built. However, the BC-8 pipe conveyor is still significant due to its high number of horizontal and vertical sharp curves and remains recognised worldwide as a remarkable material handling solution (Figs. 1 and 2).
The routing follows the natural terrain as it traverses through Eccles Canyon while transporting the coal at a speed of 4.18 metres per second. Fig. 3 shows the drive and take-up configuration.
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The main technical details of BC-8 as described in  are:
- Pipe conveyor belt: St1000 8+6, width 1600 millimetres
- Outer idler diameter: DO ≈ 452 millimetres (17.8 inch)
- Route: 22 horizontal und 45 vertical curves; min. curve radius Rmin = 365 metres (1200 feet); steepest inclination angle a = 11°
- Center distance: C-C = 3414 metres
- Take-up: gravity take-up at head
- Load/return idler spacing (straight): pl ≈ 2.27 metres (7 feet 6 inch) / pr ≈ 4.57 metres (15 feet)
- Load/return idlers spacing (curves): plc ≈ 1.83 metres (6 feet) / prc ≈ 3.66 metres (12 feet)
- Drive system: shunt DC-motors with 2 × 299 kilowatts drive power at tail plus 1 × 299 kilowatts drive power at head; max. overload 200 percent for 2 minutes
- Max. belt speed: vmax = 4.2 metres per second (827 feet per minute);
- Max. fill ratio: hF ≈ 0.7
- Design mass flow: Im ≈ 1270 tonnes per hour (1400 short tons per hour)
- Material: crushed coal ; maximum size dKmax ≈ 51 millimetres (approx. 2 inch)
- Temperature interval: -40 °C (40 °F) ≤ T ≤ +38 °C (+100 °F)
- Downhill conveyor system: difference in height between tail and head DH ≈ -172 metres (-564 feet)
Because Contitech was not involved in the design and the installation of the initial belt, the company teamed up with two partners who already had the expertise in handling this conveyor system. The first partner was the supplier of the original equipment, Thyssenkrupp Robins (TKRI), Denver (CO), USA. TKRI provided assistance in the planning of the belt replacement, the commissioning of the new belt and technical support for the necessary system maintenance to ensure that the new belt would fit into the existing structure. The second team member was Applied Industrial Technologies (AIT) from Salt Lake City (UT), USA, who knew the system and the conditions prevailing on site from various maintenance activities. AIT was responsible for all preparatory work for pulling the new belt, the belt splices and personnel during commissioning.