Solve the following questions based on the Baggage Handling Case Study in the attached photos:-

1- Estimate the following:

Wheel replacement costs

Wheel failure repair costs

Downtime penalties

Stock holding costs

2- Discuss the advantages and disadvantages of existing maintenance strategy

3- Propose a maintenance strategy that could reduce downtime costs

There is a baggage transfer system at Heathrow Airport in London, UK which operates between terminals 1&4. This moves passenger bags in either direction. It consists of 500 baggage cars which travel continuously between the two terminals on a narrow gauge railway that runs in an underground tunnel. The whole arrangement is shown schematically below. The photograph below shows one of the baggage cars with a suitcase case inside it travelling down a spiral. Failure of any one of the baggage cars would cause the whole system to shutdown. If this happens the airport incurs heavy financial penalties from the airlines. If follows therefore that the airport authorities have to ensure maximum reliability for these baggage cars. The whole system operates continuously every day of the year from 05:00 to 22:30. The baggage cars complete one complete circuit approximately every 20 minutes. Their speed does not depend on whether they are empty or full. In order to facilitate baggage car maintenance, two sets of sidings are available - one at each terminal. These sidings have workshops and special rolling roads where the cars can be test run after repairs before being re-injected into the circuit. Up to 10 empty baggage cars can be diverted to the sidings at one time without unduly affecting system performance. This allows some maintenance to be carried out during the day-shift. More extensive maintenance and any track maintenance must be carried out during the night-shift when the airport is closed. Each baggage car has eight wheels: four running wheels and four guiding wheels. All of the wheels are supplied with integral bearings. Failures of these wheels do occur, so the existing maintenance strategy for the baggage cars consists of taking each car out of service every 80 days and replacing every wheel. Each wheel with its bearings costs 20. To replace all eight wheels on a baggage car takes eight man-hours. The hourly cost for labour is 40. Given the large number of wheels which are replaced a year and their 12 week lead time from the USA, a stock level of 16,000 is maintained in a warehouse at all times. The holding cost in this warehouse is 20% of the stock value per year. In spite of operating this 80 -day wheel replacement policy some wheel failures occurred in 2022. Each failure takes 8 hours labour to fix. This triggered penalty payments to the airlines totalling 1,000,000. Failure data from the computer maintenance management system has been analysed and the following hazard curve has been produced for the baggage car wheel failures. The failure rate is approximately 2.22105 failures per hour for each baggage car. Portable vibration monitoring equipment is available within the maintenance group. It would takes approximately 1 hour to take vibration readings from all eight wheels on a single baggage car. The diagram below shows how the vibration readings increase from the onset of a problem to an actual wheel failure. This graph was what made the engineer decide on the 80 -day wheel replacement policy. A. Estimate the following: - Wheel replacement costs - Wheel failure repair costs - Downtime penalties - Stock holding costs B. Discuss the advantages and disadvantages of existing maintenance strategy C. Propose a maintenance strategy that could reduce downtime costs