to accompany CHAPTER 17: Maintenance and Reliability. Additional Homework
Problems. 17.20 The credit card issuing process at Atlanta Bank's VISA ...
Additional Homework Problems to accompany CHAPTER 17: Maintenance and Reliability
17.20 The credit card issuing process at Atlanta Bank’s VISA program consists of 10 steps performed in series by different bank employees. The average reliability of each employee is 98%. Use Figure 17.2 in the text to find the overall reliability of the credit card issuing process.
17.21 Given the probabilities that follow for Ronny Richardson’s print shop, find the expected breakdown cost. 0 1 2 3 Number of Breakdowns 0.3 0.2 0.2 0.3 Daily Frequency The cost per breakdown is $10.
17.22 You have a system composed of a serial connection of four components with the following reliabilities: Component 1 2 3 4
Reliability 0.90 0.95 0.80 0.85
What is the reliability of the system?
17.23 Cecil Bozarth Manufacturing has tested 200 units of a product. After 2,000 hours, 4 units have failed; the remainder functioned for the full 4,000 hours of the testing. a) b) c) d)
What is the percent of failures? What is the number of failures per unit-hour? What is the number of failures per unit-year? If you sell 500 units, how many are likely to fail within a 1-year time period?
17.24 Wharton Manufacturing Company operates its 23 large and expensive grinding and lathe machines from 7 A.M. to 11 P.M., 7 days a week. For the past year, the firm has been under contract with Simkin and Sons for daily preventive maintenance (lubrication, cleaning, inspection, and so on). Simkin’s crew works between 11 P.M. and 2 A.M. so as not to interfere with the daily manufacturing crew. Simkin charges $645 per week for this service. Since signing the maintenance contract, Wharton Manufacturing has noted an average of only three breakdowns per week. When a grinding or lathe machine does break down during a working shift, it costs Wharton about $250 in lost production and repair costs. After reviewing past breakdown records (for the period before signing a preventive maintenance contract with Simkin and Sons), Wharton’s production manager was able to summarize the following patterns: Number of breakdowns per week Number of weeks in which breakdowns occurred
1 2 3 4 5 6 7 8 1 3 5 9 11 7 8 5 Total weeks of historical data: 50
The production manager is not certain that the contract for preventive maintenance with Simkin is in Wharton’s best financial interest. He recognizes that much of his breakdown data are old but is fairly certain that they are representative of the present picture. What is your analysis of this situation and what recommendations do you think the production manager should make?