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|  17.1.4 Inspection Interval The inspection interval should be determined by the application of the equipment and the environment in which it works. Inspections of self propelled box conveyors may be needed more often because of the complexity of the system, while the selective vertical conveyor is more rugged and less complex in design. Neither type unit should be inspected at less than 6 month intervals. 17.2 INSPECTION OF SELF-PROPELLED BOX CONVEYOR 17.2.1 General Description The self propelled box conveyor system is made up of an assortment of various parts that are assembled to suit a specific application. The system could be as simple as the type shown in Figure 17-3 or more complex as that shown in Figure 17-1. The carriers are independently powered modules that move from a point to a selected destination by way of a track system. It is capable of moving in both a horizontal and vertical direction. The module is powered by a series of bus rails that are located in the track. The system is operated by establishing a destination on the module and giving it a start signal. The module will proceed into the track system. At various discussion points along the way, the destination is automatically read and the track path is adjusted accordingly until the module arrives at its destination. There are several manufacturers of this type of equipment. The basic concept is the same. However each manufacturer has a different approach to accomplishing the result. We will try to show the various designs as we proceed. Because there is no one standard system design, we will address our inspection to the various components. The inspector will have to tailor his/her inspection procedure to suite the specific system he/she is inspecting. 17.2.2 Track 17.2.2.1 Design. The system uses modular, extruded aluminum track sections. Two of the track power rails provide 24 volt D.C. power to the module motors, while the third rail feeds control logic commands. Horizontal car movement relies on friction drive, while vertical movement engages gearing between the track and the module. Figure 17-4 show three basic track designs used today. 17-4 |  | |
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