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

Usually the system is operated at 80 percent of the maximum belt speed. Other speeds, as shown in Fig. 18, are commissioning presets. The power demand of the system follows the belt speed almost linearly; therefore the resistance to motion in the system is not influenced by the belt speed.

When the new belt was operated for the first time, without material, during the initial commissioning of the system, approximately 90 percent of nameplate motor power was used when running at 90 percent at full speed.

After the break-in period was over, the power consumption dropped by approximately 30 percent during the same warm season. This behaviour is a result of the transversal rigidity of the pipe belt and its high forming forces at the beginning of the break-in period. The power consumption reduces as the belt adapts to the conveyor system.

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Furthermore, from Fig. 18 it is evident that the temperature has a very strong influence (over 20 percent) on power consumption. This can be explained by the increase of the transversal rigidity of the pipe Conveyor belt (rubber becomes stiff when cold) and the escalation of the general friction in the conveyor system (e.g. idlers) at low temperatures.

Fig. 19 shows the power consumption during commissioning, after commissioning and after the break-in period when loaded in summer. All these measurements were made at temperatures of approximately +15 °C (59 °F), to avoid the temperature influence on the results.

During commissioning, with material, the system’s power demand in the loaded condition was approx. 75 percent of the installed motor power. After nearly two weeks of operation, this value had reduced by approx. 11 percent.

After the break-in period, the power consumption dropped by another 18 ercent. Consequently, the difference in the power consumption between the commissioning time and the time after break-in is approx. 30 percent. As mentioned previously, the high transversal rigidity of the pipe belt reduces over time. This is a result of the belt running and adapting to the conveyor system over several months of initial operation.

In the winter, the belt continues to operate with sufficient safety factors, showing the highest belt tension at the tail pulley in the return strand.

Since the day of commissioning, the system has operated with outstanding stability, regardless of the circuitous routing. The belt overlap in all sections is steady and keeps the desired 12- and 6-o’clock-position in the carry and return strand, respectively. Even with the sections partially loaded the behaviour of the belt is stable, showing that under the given challenging circumstances (downhill application, age of the system, condition of idlers, curved routing) the belt for this pipe conveyor application is obviously the determining element for the safe operation of the system.

Conclusion

The installation and commissioning of the new pipe conveyor belt was successfully completed within less than 6 weeks, thanks to the excellent and professional cooperation within the project team consisting of Contitech Conveyor Belt Group, Thyssenkrupp Robins, Applied Industrial Technologies and Skyline Mine.

After the commissioning of the pipe conveyor belt in 2006 and until now, despite some challenging circumstances (downhill conveyor, age of the system, condition of idlers, curved routing), the tracking and overall behaviour remains absolutely stable.

For this specific pipe conveyor application, the belt construction is determinative for the safe operation of the conveyor system, as a whole. Even with partially loaded belt sections, no change in the belt’s behaviour was observed. This indicates that the combination of belt design and the excellent performance of all team members during the planning, splicing, belt installation and commissioning resulted in the successful completion of the belt replacement.

The difference in the power consumption between the commissioning time of BC-8 and the period of time after break-in is approx. 30 percent. The resultant optimal performance is due the reduction of the high transversal rigidity of the pipe belt in combination with the belt adapting to the conveyor system during the first few months of operation.

The temperature has a very strong influence on the power consumption. In the winter, the power consumption of a pipe conveyor is more than 20 percent higher than in during the summer. This is because of the increased transversal rigidity of the pipe conveyor belt (rubber becomes stiff when cold) and by increasing of the general friction in the conveyor system (e.g. idlers) at low temperatures.

Consequently, both a pipe conveyor and a pipe conveyor belt should be designed with consideration of higher friction forces during commissioning/break-in period as well as at low temperatures.

At this point authors would like to thank the mine manager Mr. Sorensen and the Skyline Mine employees for their contribution to this project. n

References

[1] Neubecker, I.: An overland pipe conveyor with 22 horizontal and 45 vertical curves connecting coal mine with rail load out. bulk solids handling Vol. 18 (1998) No. 3, pp. 457-462.

[2] Keller, M: Zur Optimierung hochfester Stahlseilgurtverbindungen. Ph.D. Thesis, Universität Hannover, Hanover 2001.

[3] Keller, M: Installation of a conveyor belt for hard coal shipments with optimized energy consumption in Kalimantan. Surface Mining Vol. 55 (2003) No. 2., pp. 177-184.

[4] Kahrger, R., et al.: Henderson 2000 – a world class conveying system. bulk solids handling Vol. 20 (2000) No. 3, pp. 319-322.

[5] Keller, M., Alles, R.: The impact of the German Standard DIN 22101 on belt conveyor design. 2004 SME Meeting & Exhibit Denver, Colorado, USA.

[6] Vidal, S., Vidal, R.: Differentiating between DC and AC motors. EC&M Electrical Construction & Maintenance Vol. 106 (2007) No. 2, p. 16.

[7] DIN 22 101: Stetigförderer. Gurtförderer für Schüttgüter. Grundlagen für die Berechnung und Auslegung (Continous mechanica handling equipment; belt conveyors for loose bulk materials; basis for calculation and dimensioning). Beuth-Verlag, Berlin, Köln, 1982.

[8] DIN 22 101: Stetigförderer. Gurtförderer für Schüttgüter. Grundlagen für die Berechnung und Auslegung (Continous conveyors – Belt conveyors for loose bulk materials – Basics for calculation and dimensioning). Beuth Verlag, Berlin, Köln, 2002.

* Dr.-Ing. Andrey Minkin  The author is Application Engineer and Project Manager at Contitech Conveyor Belt Group, Germany

* * Dr.-Ing. Andreas Jungk  The author is responsible for application engineering and belt monitoring systems at Contitech Conveyor Belt Group

* * * Thomas Hontscha  The author works as Supervisor and Splicer at the Service Centre of Contitech Conveyor Belt Group, Germany,

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