Belt Replacement at a Long Distance Pipe Conveyor at the Skyline Mine

Conveyor Maintenance

Belt Replacement at a Long Distance Pipe Conveyor at the Skyline Mine

Belt Design, Installation and Power Measurements
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.
(ed. WoMaMarcel - 18/10/2014)
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Fig. 1: Pipe conveyor routing seen from the head end.

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 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 m above sea level and transports coal at 1270 t/h over a distance of approx. 3400 m 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 m.

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 [1]. The turnkey project included the design, delivery, installation and commissioning of the pipe conveyor belt.

Project Details

Upon initial installation, the Skyline Mine Overland Pipe Conveyor BC-8 was the highest capacity and second longest steel 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).

Fig. 2: Pipe conveyor routing seen from the tail end.

The routing follows the natural terrain as it traverses through Eccles Canyon while transporting the coal at a speed of 4.18 m/s. Fig. 3 shows the drive and take-up configuration.

Fig. 3: Drive and take-up configuration of the BC-8 pipe conveyor.

The main technical details of BC-8 as described in [1] are:

  • Pipe conveyor belt: St1000 8+6, width 1600 mm
  • Outer idler diameter: DO ≈ 452 mm (17.8 in)
  • Route: 22 horizontal und 45 vertical curves; min. curve radius Rmin = 365 m (1200 ft); steepest inclination angle a = 11°
  • Center distance: C-C = 3414 m
  • Take-up: gravity take-up at head
  • Load/return idler spacing (straight): pl ≈ 2.27 m (7 ft 6 in) / pr ≈ 4.57 m (15 ft)
  • Load/return idlers spacing (curves): plc ≈ 1.83 m (6 ft) / prc ≈ 3.66 m (12 ft)
  • Drive system: shunt DC-motors with 2 × 299 kW drive power at tail plus 1 × 299 kW drive power at head; max. overload 200 % for 2 minutes
  • Max. belt speed: vmax = 4.2 m/s (827 ft/min)
  • Max. fill ratio: hF ≈ 0.7
  • Design mass Zow: Im ≈ 1270 t/h (1400 st/h)
  • Material: crushed coal
  • Maximum size dKmax ≈ 51 mm (approx. 2 in)
  • Temperature interval: -40°C (40°F) ≤ T ≤ +38°C (+100°F)
  • Downhill conveyor system: difference in height between tail and head DH ≈ -172 m (-564 ft)

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