1、 Acta Montanistica Slovaca Ronk 6(2001),2,150-157 Resistances to the motion in mining belt conveyors Jerzy Antoniak1 Research workers of the Silesian Technical University(Antoniak,Lutyski,1999)have been carrying out measurements on mining belt conveyors for years.The tests covered belt conveyors cha
2、racterized by considerable lengths and high capacities,complicated configurations of a conveyor route and equipped with driving systems of different type in which soft starting facilities were incorporated or not included.One of the objectives of the tests was to determine quantities of principal re
3、sistances to motion the results of which have been presented in this paper.Key words:mining,principal resistances to motion,belt conveyor,field measurements.Decrease-oriented tendency in resistances to the motion in belt conveyors The results of a great number of field measurements taken on belt con
4、veyors allow to conclude that a high accuracy of calculations of principal resistances to the motion is obtained when using a basic method as described in the standard DIN 22101 on condition that the coefficient f of principal resistances to the motion has been properly selected.Among principal resi
5、stances to the motion are included:resistances to idler rotation,indentation rolling resistances,flexure resistance of the belt and flexure resistances of bulk material.The coefficient of principal resistances to the motion f combines the force of gravity of a sum of masses being in motion with prin
6、cipal resistances to the conveyor motion FP,N thus FfgmP=N where m sum of moving masses,kg,g acceleration corresponding to the force of gravity,m/s2.It is considered that a standard quantity is f=0.02 but in the case of underground mining f=0.025 or f=0.03.Among lumped resistances of a conveyor FL,N
7、 are included:resistances to belt bending on drums,rotation resistances of all drums,resistances when loading the material to be conveyed,and resistances of belt cleaners.Lumped resistances are expressed as a coefficient of length C:()CFFFFFPLPL=+=+/1 PCombining C and f together brings about FFC fgm
8、PL+=N When taking into consideration additional resistances produced e.g.by advancing arrangement of idlers in relation to the direction of the belt movement FA,N and resistances of lifting and lowering of the material being conveyed FLL,N a total resistance to the motion is obtained which allows to
9、 determine the drives power.A distribution of the power consumption given in percentage of power used to overcome particular resistances to the motion in long belt conveyors laid horizontally(of about 1.5 km in length)is presented in fig.1.Recently a lot of attention is given to the problem of decre
10、asing the power consumption in drives of a belt conveyor.This purpose was achieved by the application of drives controlled with frequency converters,introduction of special idler sets resulting in the reduction of resistances to the belt bending and of rolling resistances as well as in consequence o
11、f the use of special cover plies made from synthetic plastics characterized by decreased rolling resistances.The experience of the Goodyear Company gained in the course of selecting the Fig.1.Conveyor power consumption for long horizontal profiles 1 indentation rolling resistance,2 flexure resistanc
12、e of bulk material,3-flexure resistance of the belt,4 bearing resistance of the idler,5 secondary resistances,6 extraordinary resistances 1 Prof.zw.Dr hab.in.Jerzy Antoniak,Politechnika lska,Gliwice Polsko (Recenzovan a revidovan verzia dodan 14.8.2001)150 Acta Montanistica Slovaca Ronk 6(2001),2,15
13、0-157 materials for tyres finds an application here.The reduction of power consumption in conveyor drives as shown in fig.2 is a result.In order to reduce the power requirement for drives of long underground belt conveyors,the number of tilting idlers in the top strand is limited.The tilting is usua
14、lly of 1.5 to 2.5o and its role is to align the belt run.From field measurements of such conveyors(Sotysik,1999)it appears that reduction of the number of idlers covering an advance in the top strand by 63,62%has brought about a decrease in the power requirement shown in fig.3.Fig.2.Power consumptio
15、n by the belt conveyor with the belt made from materials of low-rolling resistance(Belt Conveyors for Bulk Materials).Fig.3.Conveyor power consumption for long horizontal profiles equipped with 100%tilting troughing idlers(curve a)and with 36,4%of tilting troughing idlers in the upper strand(curve b
16、).The detailed calculations have indicated that in case of an empty conveyor the resistance to the motion produced by the advancing arrangement of side idlers(being here of 2.5o)in the top strand can be calculated with a high accuracy using the formulae by prof.Vierling(Antoniak,1992).The resistance measured on one set amounted to about 2.12 N and the calculated was of 2.23 N.Whereas in case of a conveyor loaded to about 40%of the nominal load capacity the measured resistance to motion was about
