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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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 PE can be calculated as:

PE = IARM · UARM


Fig. 16: Display of the system's inverters.

Fig. 17: Scheme of a Shunt DC-Motor.

The electrical power efficiency hE is estimated as:

hE = PMn/PEn = PMn/(IARMn · UARMn)

where PMn = 299 kW is the nominal mechanical power of the motor according to the motor label, IARMn = 626 A is the nominal current according to the motor label, UARMn = 500 V is the nominal voltage according to the motor label, PMn = IARMn · UARMn = 313 kW is the nominal electrical power of the motor, and hE = 0.96 is the electrical power efficiency at rated frequency.

The mechanical power PM is:

PM = PE · hE

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

PD = PM · hM = PE · hE · hM

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

PD = F · v

Knowing the value of the power required by a belt conveyor PD 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. PE/PEn [%]) dependent on the belt speed, in percent of maximum belt speed (i.e. v/vmax [%]) without material.


Fig. 18: Power consumption versus belt speed during commissioning and after the break-in period in summer and winter.

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.

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