1、PDF外文：http:/ Solids Handling, 2004, 24(1): 16-22.Strategies for Automated Maintenance of Belt Conveyor Systems Prof.dr.ir.GabrielLodewijks DeIftUniversity of Technology, the Netherlands SUMMARY This paper discusses automation of maintenance of belt conveyor systems, in particular of idler rolls. Aut
2、omation of maintenance is a promising alternative for outsourcing maintenance, in particular when looking at the efficiency, accuracy, and costs. In order to optimise maintenance efforts, the concept of intelligent maintenance is introduced. The powered maintenance trolley that can travel autonomous
3、ly over the structure of a belt conveyor is adapted as a platform of the maintenance system. On this trolley, data acquisition equipment for vibration analysis is installed. Data mining can be done either on board of the trolley or in a central computer depending on the maintenance strategy. The opt
4、imum maintenance strategy is determined by a logistic simulation model that accounts for the lay-out of the belt conveyor itself and the accuracy of the information on the remaining lifetime of its components. INTRODUCTION Today more and more companies outsource maintenance in an attempt to balance
5、the budget and reduce the number of permanent staff members. Outsourcing maintenance however only works if the company that takes over maintenance employs well-trained and experienced personnel that stays on a specific job for a considerable time. Unfortunately, reality is different and many compani
6、es have poor experiences with external companies performing maintenance. In general, maintenance on belt conveyor systems can be divided into inspection or condition monitoring of the total system and replacement and/or reparation (in short servicing) of its components. Most problems experienced wit
7、h outsourcement of maintenance are associated with the inspection or condition monitoring of a system. It is not trivial to access the status of sometimes moving components of a belt conveyor. The same experienced person should therefore carry out inspections on a regular basis. To overcome operatio
8、nal problems caused by a lack of experience of external maintenance personnel, the inspection of belt conveyor components can be automated. In this way knowledge of for example wear rates and replacement schedules can be built up in a data base system. The external maintenance crew then can be used
9、to replace the worn off components. Alternatively, replacement of components can be automated as well. This paper discusses strategies and techniques for automated maintenance of belt conveyor systems. Section 2 defines the concept of intelligent maintenance, Section 3 discusses existing inspection
10、systems that can be used in automated maintenance systems. Section 4 discusses means of assessing the status of rotating components of belt conveyors based on vibration based monitoring concepts. Section 5 presents a case study and section 6 finally lists the conclusions and recommendations. INTELLI
11、GENT MAINTENANCE Maintenance on belt conveyor systems can be divided in condition monitoring of the total system and servicing of its components. Condition monitoring is defined as the continuous or periodic measurement and interpretation of data to indicate the condition of a component to determine
12、 the need for replacement or servicing. Condition monitoring therefore deals with the acquirement of data (data acquisition or DAQ) from sensors, the interpretation of that data (data mining or DAM) and with taking corrective actions (ACT) on components that are to fail, thus preventing fail systems
13、 from developing and propagating. The basic concept of condition monitoring is to identify subtle changes in operation, such as increased vibration levels, that indicate a mechanical (or electrical) problem is starting to develop. These early messages provide more time to plan for machine downtime a
14、nd repair. There are four typical types of maintenance: preventive maintenance: calendar based, i.e. activities are planned depending on working hours or at certain time intervals (scheduled maintenance)； it may be based on observed deterioration of components； nothing is repaired but preventive job
15、s are done. random maintenance: opportunity based, i.e. maintenance is done when the opportunity arises； the decision to maintain a component based on opportunities may or may not be triggered by the condition of a component. corrective maintenance: emergency based, i.e. repairing when
16、 a component malfunctions； this may cause a general shutdown of the system； the repair activity was not scheduled beforehand. predictive maintenance: condition based, i.e. components are being monitored and when irregular factors are discovered, one waits until a maintenance opportunity arise
17、s； it is a planned and corrective maintenance. From the above given four types of maintenance it is clear that only a predictive maintenance concept qualifies for application in an intelligent maintenance system that enables maintenance automation. Intelligence here is defined as the ability t
18、o make decisions based on information gathered through sensors in the equipment or provided by the control system of the total transport system. Applied to belt conveyor systems the information gathered from a system is information on the life expectancy of individual components as for example idler
19、 rolls. This information leads to a decision either to inspect a certain idler station and its rolls more frequently or to change a roll for a new roll. Repairing in fact here means changing one roll for another. Whether or not a roll can be repaired and the effect of that on the belt conveyors perf
20、ormance is outside the scope of this study. The main issue in this study is the question how an automated inspection strategy is affected by the accuracy of the data acquired. In theory there are two outer limits in predictive maintenance. The first is that no accurate information of the rolls is av
21、ailable at all, basically meaning that an assessment of the remaining lifetime is made purely on the basis of historical data provided by the roll or bearing manufacturers (predictive maintenance based on statistics). The second is that during inspection very accurate information on the status of ro
22、lls is generated enabling an accurate assessment of the remaining lifetime of an individual roll (predictive maintenance based on data). A logistic simulation model is made to determine the effect of the accuracy of data acquired on automated inspection strategies. This model is discussed in Section
23、 5. EXISTING INSPECTION SYSTEMS One problem faced with inspection or condition monitoring of components of belt conveyors, including the belt, pulleys and idler rolls, is that they rotate. Since the condition of components like rolls and pulleys can only be assessed when they are rotating, only cond
24、ition monitoring systems based on vibration analysis or acoustical monitoring can be used. The opposite holds for the belt. The belts condition can only be inspected when the belt conveyor system is not operating. Either way, an inspector has to walk the full length of the conveyor to inspect its co
25、mponents. An associated problem is that pulleys may be far apart from each other or that the conveyor has a great length. To ease inspection in these cases a powered maintenance trolley can be used for inspection purposes. The concept of a powered maintenance trolley is not new. An early example of
26、a maintenance trolley used on a belt conveyor system was the trolley used on the 100 kmPhosboucraa overland system built by Krupp in the 70-ties to transport raw phosphate across a distance of 100 km from inside the west Sahara across a desert of stones to the loading point on the coast. This long-distance conveyor system, consisting of belt systems with centre distances of 6.8 to 11,7 km. applied a maintenance trolley concept to allow for inspection also see Figure 1. The Krupp-design turned out to be occasionally liable to instability.
