| Belt conveyor has many advantages: long transport distance, high transportcapacity, low running resistance and power consumption, easy to be maintained, lessoperators needed and so on, so it is widely used in the coal transportation in modernlarge coal mines and runs effectively. However, for various reasons, some commonmalfunctions like longitudinal tear, belt-breaking, belt slip and deviation might occur inits operation and bring serious consequences. Therefore it is quite important to identifythe reasons for these malfunctions and find the solution in time. Based on this, severalstudies were conducted in this paper as follows:1.The various causes and influences of longitudinal tear, belt-breaking, belt slipand deviation and other malfunctions were analyzed respectively, and the commonsolutions to each problem were classified and summarized.Particularly,theelectromagnetic inductive longitudinal rip detection scheme and vertical-roll typeautomatic offset adjusting scheme were discussed in detail, including their operationalprinciples, structure of devices, sensor selection and application, and signal acquisitionand analysis. By comparing the advantages and disadvantages of each scheme, the bestdetection method was designed.2. An integrated detection method based on velocity detection for belt-breakingand slip problem was proposed. It is proved that some similar changes will happen tothe velocity of belt, rollers and idler pulleys when belt-breaking or slip takes place.Based on this character, a few velocity sensors were mounted at driving pulley, drivenpulley, up belt and down belt, respectively, to detect their velocity change, and then tojudge if belt-breaking or slip occurs. The velocity sensor selected in this paper wasencoder.3. A comprehensive belt conveyor running status monitoring scheme based onPLC(Omron, SYSMAC CP series, CP1H XA) was developed, containing several partsas follows:(1) The output signal of electromagnetic inductive longitudinal rip detectiondevices was converted to square waves and sent to PLC high-speed counter, thencompared with the reference signal to judge whether longitudinal rip take place or not.The induction coil position was identified by the position detectors mounted at thedetection device. (2) The output signal of velocity encoders applied to detect belt-breaking and slipwas sent to PLC high-speed counter, analyzed by the program to decide whether thevelocities were normal, and to judge whether belt-breaking or slip take place or not.(3) The output voltage of belt deviation detector was sent to PLC analog inputthrough the transmitter, analyzed by the program to judge if any deviation occurs, andthe deviation adjust device would be started or not according to the program result. |
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