Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

R.E.M. Koenis Simulatie onderhoudsrobot voor een bandtransporteur.
Computer program, Report 2002.LT.5668, Transport Engineering and Logistics.

A strategy for a maintenance robot for a conveyor belt has been drawn up by K.H. Wallien ("Onderhoudsstrategie van een onderhoudsrobot voor bandtransporteurs", report 2002.LT.5602 (in Dutch)). This strategy explains how the maintenance robot (BOR) has to inspect and if necessary replace rolls in a conveyor. The strategy has two possibilities of how to inspect the rolls:
  1. The inspection is more frequent when the roll gets to the end of its lifetime. (Flex)
  2. There is a continuous inspection, regardless of the condition of the bearing. (Fixed)
Furthermore, there are three different plans for the maintenance robot to carry out the inspection and replacement activities:
  1. The maintenance robot carries out the inspection and the replacement activities on the outward journey, and has no activity on the inward journey. (I+OèXç)
  2. The maintenance robot carries out the inspection and the replacement activities on the outward journey and on the inward journey. (I+Oçè)
  3. The maintenance robot carries out the inspection on the outward journey and the replacement activities on the inward journey. (IèOç)
The combination between two inspection strategies and three inspection and replacement strategies gives a total of six possibilities. To determine which of these possibilities is the best, a program has been developed that simulates these six situations. During the development of the program, the proposed strategies have been maintained.

The program uses a graphic interface. In this interface the variables for the actual simulation can be modified. Since the minimum and maximum lifespan of the bearings and the relation in-between is not yet known, it is not possible to make an accurate simulation.

It is possible after the simulation to make a comparison between the different inspection and movement plans. This gives some interesting results. The assessment of these results is given in table SE.1. Extra care has to be taken when comparing the assessment of the broken bearings with the assessment of the cycle time, because the costs for the BOR are unknown. It might be better to let the BOR make extra movements or to replace bearings.

    Table SE.1: Assessment of the performance of the plans in the simulation
    Inspection plan
    No broken bearings Cycle time
    #days to early length VT length BT #cycles #length
    Flex (I+OèXç) +/- +/- + + +
    Flex (I+Oçè) - - + + +
    Flex (IèOç) - - + + +
    Fixed (I+OèXç) + + NA - +
    Fixed (I+Oçè) +/- +/- NA - +
    Fixed (IèOç) + +/- NA - +

The first conclusion that can be drawn, is the proposed times for the start time of the inspection and the replacement in the maintenance strategy by Wallien can not be maintained if the goal is that there shouldn't be any rolls replaced after they brake down. Therefore, there is a possibility in the program to specify the start time of the inspection and the replacement time separately.

Secondly, it seems that there is a decrease in the number of movements when inspection plan Flex is used. If it is not desirable to have the robot active all day, then inspection plan Flex has an advantage over inspection plan Fixed.

The third conclusion that can be drawn is that the rolls replaced in movement scheme Fixed are replaced later than in scheme Flex. The average number of days until the rolls brake down is lower. This means that the rolls last longer and a cost reduction can be realized.

It is shown in table SE.1 that Flex (I+OèXç) and Fixed (I+OèXç) are the two plans working well. Therefore it will depend on the costs of the BOR which plan will work best.

Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2004.06.20; , TU Delft / 3mE / TT / LT.