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Question1: From your own perspectives, answer the questions raised at the end of the "Ethical Dilemma" case at the end of Chapter17. This should take two to three paragraphs.
Question2: Consider a product that is "settled in." Its MTBF distribution has been found to be normal with a mean of 10,000 hours and a standard deviation of 100 hours. What is the probability of a breakdown before 8,000 hours? Before 9,000 hours? Would you prefer a policy of preventive maintenance, or a policy of breakdown maintenance, on this product? Explain your choice. Please note that a good logical explanation is critical in this discussion.
Question3: Answer Problem 17.4 (a, b, c, & d) at the end chapter 17. Show all the steps in your responses to each of the four questions. use of preventive maintenance and excellent repair facilities Firms give employees “ownership" of their equipment, When workers repair or do preventive maintenance on their downs are less common. Well-trained improves quality and performance to schedule. Top firms build and maintain systems that drive out variability so that customers can rely on products and services to be produced to specifications and on time. Speed eyTerms Redundancy (p. 665) Preventive maintenance (p. 667) Breakdown maintenance (p. 667) Infant mortality (p. 667) Maintenance (p. 662) Reliability (p. 662) Mean time between failures Autonomous maintenance (p. 670) Total productive maintenance (TPM) (p. 671) (MTBF) (p. 664) Ethical Dilemma The space shuttle Columbia disintegrated over Texas on its 2003 return to Earth. The Challenger exploded shortly after launch in (seals cracking in cold weather, heat shielding tiles falling off 1986. And the Apollo 1 spacecraft imploded in fire on the launch toos left in the capsule), should astronauts have been allowed pad in 1967. In each case, the lives of all crew members were to fly? (In earlier Atlas rockets, men were inserted not out of lost. The hugely complex shuttle may have looked a bit like an necessity but because test pilots and politicians thought they airplane but was very different. In reality, its overall statistical should be there.) What are the pros and cons of staffed space reliability is such that about 1 out of every 50 flights had a major exploration from an ethical perspective? Should the U.S. spend malfunction. As one aerospace manager stated, "Of course, you billions of dollars to return an astronaut to the moon or send can be perfectly safe and never get off the ground." Given the huge reliability and maintenance issues NASA faced one to Mars? Discussion Questions 1. What is the objective of maintenance and reliability? 2. How does one identify a candidate for preventive maintenance? 3. Explain the notion of "infant mortality" in the context of 5. What is the trade-off between operator-performed mainte- 6. How can a manager evaluate the effectiveness of the mainte- 7. How does machine design contribute to either increasing or nance versus supplier-performed maintenance? nance function? alleviating the maintenance problem? product reliability 4. How could simulation be a useful technique for maintenance problems?
Explanation / Answer
Question 1:
Ethical dilemma- Columbia
Manned space shuttles help us to understand how human bodies behave and react in space. They also help us to explore the possibilities of sending and inhabiting the planet in future. The technologies developed for such human use are being reproduced for industrial and domestic use. Also, the biological science and research done for staffing and sending the astronauts long distance have been applied in medicine. Since future is unpredictable, this may be the only possibility for exploring space now for future inhabitation.
At the same time, such manned explorations are every expensive compared top robot explorations. Also, training astronauts is very expensive not mention the risks of lives involved in manned exploration. Since men have ale eady been sent to zero gravity locations, repeating them is only a waste of resources and such stints have used for publicity, rather than pure research
Returning an astronaut to the moon is an expensive procedure. It is just repeating the same experiment again and again with very little gains compared to costs and risks. But sending a man to Mars is a totally different goal with huge implications in future. Since mars are considered to be inhabitable, this proves valuable for mankind. Hence sending a man to Mars is a better one
Question2:
Consider a product that is "settled in." Its MTBF distribution has been found to be normal with a mean of 10,000 hours and a standard deviation of 100 hours. What is the probability of a breakdown before 8,000 hours? Before 9,000 hours? Would you prefer a policy of preventive maintenance, or a policy of breakdown maintenance, on this product? Explain your choice. Please note that a good logical explanation is critical in this discussion.
Meantime to failure- shows the expected time to failure for a system
SD for 8000 hours= (8000-10000)/100 =-20
SD for 9000 hours = (9000-10000)/100 =-10
The specified times are far away from the mean. In a normal distribution table, the probabilities of those occurrences are zero. Hence a policy of preventive maintenance is preferable.
Question 3:
a.
product failure rate (FR). - percentage of failure among the total number of product tested
FR (%) =(Number of failures/ Number of unit tested) *100
=(5/100) *100 = 5%
b)
Number of failures per unit-hour, FRN = (Number of failures)/ (Total Operating time)
Total time = 5000*100 = 500000 unit hours
Non operating time = 2500*5 = 12500 hours (2500 because test is run halfway)
Total Operating time =Total time - Non operating time = 500000-12500= 487500
Number of failures per unit hour = 5/(500000-12500) = 5/ 487500 = 0.000010256
= 0.00001026 failures / unit hour
(c) Number of failures per unit year:
Failure per unit-year
= Number of failures per unit hour x 24 hr/day x 365 days/yr
= 0.00001026 X 24 X 365
= 0.089846
=0.08985
(d) Failures in 1100 units
= 1,100 units X 0.08985
= 98.835 failures / year
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