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

Commissioning of the new Pipe Conveyor Belt

After the installation had been finished, the commissioning of the conveyor system started. The plan of the project team included:

• commissioning of the unloaded conveyor system,

• making all necessary adjustments and reassembling all dismantled structures at the head end, and

• commissioning of the system with progressively increased speed and filling ratio.

The behaviour of the belt during the pulling procedure was very positive. The overlap was oriented in the 12-o’clock and 6-o’clock position in the carry and return strand, respectively, at almost every position. Consequently, no preparative work was required prior to starting the conveyor. After tensioning and empty operation for several revolutions, the belt ran very stable with the overlap at 6- and 12-o’clock positions at every speed and had a contact to all six idlers present in the panel, as pictured in Figs. 14 and 15. Therefore, the belt made the full cross-section of the system available for coal transport, as intended. In addition, the overlap remained tightly closed between the idler stations. Since the belt approached the pulleys without any problems, no changes to the system, regarding belt tracking, were necessary and the efforts for the commissioning of the conveyor were minimised.

During the following step of the commissioning, the belt was loaded at several fill ratios and speeds.

Gallery

Gallery with 23 images

Power Measurements during Comissioning and Break-in

Contitech performed power measurements several times; during the commissioning, after 13 days (during the break-in period), and after the break-in period was over in the summer and winter. The idea was to collect information concerning friction forces in the conveyor system at different times during the operation period. This helps OEMs to design pipe conveyors more efficiently.

For this purpose power readings were taken from the system’s inverters at the mine site (Fig. 16). For a shunt DC-motor (Fig. 17), the electrical power consumption P_E can be calculated as:

P_E = I_ARM · U_ARM

The electrical power efficiency h_E is estimated as:

h_E = P_Mn/P_En = P_Mn/(I_ARMn · U_ARMn)

where P_Mn = 299 kilowatts is the nominal mechanical power of the motor according to the motor label, I_ARMn = 626 amperes is the nominal current according to the motor label, U_ARMn = 500 volts is the nominal voltage according to the motor label, P_Mn = I_ARMn · U_ARMn = 313 kilowatts is the nominal electrical power of the motor, and h_E = 0.96 is the electrical power efficiency at rated frequency.

The mechanical power P_M is:

P_M = P_E · h_E

The power required by a belt conveyor P_D that has to be transmitted to the conveyor belt by drive pulleys at the rated frequency is calculated as:

P_D = P_M · h_M = P_E · h_E · h_M

where the mechanical power efficiency: h_M ≈ 0.97. The power required by a belt conveyor P_D from the motional resistance F and the belt speed is calculated as:

P_D = F · v

Knowing the value of the power required by a belt conveyor P_D and the belt speed v, the motional resistance F, consequently, the DIN-f factor can be calculated [7, 8]. For this purpose, specific software like Beltcon (Contitech), Beltanalyst (Overland Conveyor Company), or similar design software can be helpful.

Fig. 18 shows the results of the measured electrical power consumption in percent of the nominal electrical power of motor (i.e. P_E/P_En [%]) dependent on the belt speed, in percent of maximum belt speed (i.e. v/v_max [%]) without material. These measurements were performed with the help of inverters of the BC-8-Pipe Conveyor (Fig. 16) during commissioning and after the break-in period. Additional power readings were performed in summer (T ≈ +15 °C (59 °F)) and in winter (T ≈ -14 °C (7 °F)), after the break-in period was over, to investigate the temperature influence of friction in the system and the transversal rigidity of the pipe belt.

The Contitech experience shows that the total break-in period can take up to several months when the belt is running. When the break-in period is over, the measured power consumption level remains constant for several months during the same season of the year.

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