production management

LESSON 2 EXERCISES Reliability

Production Management

ASSIGNMENT 2

1. From articles 1 (part 1 and 2), article 2 and article 3, (from the book Principles of Operations Management, Eigth

edition, Heizer and Render, Pearson) answer the following questions:

a. How does the concept of product life cycle apply to Regal Marine products?

b. What strategy does Regal use to stay competitive?

c. What are the likely benefits of the CAD design technology?

2. There is a plant where computers are produced. So, 25 computers are working 3.000 hours. We checked that 8

computers failed. From this 8, there were 4 that failed after 1.200 hours, then 2 of them failed after 1.800 hours and

the last 2 failed after 2.400 hours. Calculate the reliability, the percentage of failures, the number of failures and the mean

time between failures.

3. In an industry plant, they are evaluating 500 units of an electronic component that were working 10 hours. On the

final report, we could read that the reliability is really high. And we could see the following information. Mean time

beetwen failures 20 hours. Number of components that failed 20. Please calculate the reliability.

4. The reliability analysis of a bike carried out during 2.000 hours (total time), has concluded that from 1000 units, only

20 have failed. Choose the correct answer:

a. The reliability is 98%

b. If the non operation time is 20h, we obtain 0,01 failures per hour.

c. If the operation time is 1980 hour, we obtain 10 failures per 1000 hours working.

d. All the answers are correct.

5. A manufacturer of disk drives or notebook computers wants a Mean time between failures of at least 50.000 hours.

Recent test results for 10 units were on failure at 10.000 hours, another at 25.000 hours and two more at 45.000 hours.

The remaining units were still running at 60.000 hours. Determine the percent of failures, the number of failures per unit-

hour and MTBF at this point in the testing.

6. A Light bulb producer tell us that the reliability is 99,99%. A) What does it mean? After checking them we realize that

between 100.000 bulbs (working 1.000 hours) only 900 bulbs failed. B) Could we still saying that the reliability is

99,99%? After checking it, the mean time between failures was 24 hours. C) Calculate the number of failures per

operation time.

7. In an assembly chain we have 3 “stops” per week. The chain works 24 hours per day but only 5 days per week. In

order to restart the chain it is necessary to spend a mean time of 30 minutes. They want to hire a new specialist in

order to reduce the restarting time of the machinery. This specialist tell us that with his advice the machinery will

achieve a reliability of 99,95%. Should we accept his offer?

8. The failure rate is 5%. Choose the correct answer:

a. The reliability is higher than 100%

b. If they have produced 110 units, 5 have failed

c. The reliability is 95%

d. None of them are correct.

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LESSON 2 EXERCISES Reliability

ASSIGNMENT 2

1. From articles 1 (part 1 and 2), article 2 and article 3, ( from the book Principles of Operations Management, Eigth edition, Heizer and Render, Pearson ) answer the following questions: a. How does the concept of product life cycle apply to Regal Marine products? b. What strategy does Regal use to stay competitive? c. What are the likely benefits of the CAD design technology?

There is a plant where computers are produced. So, 25 computers are working 3.000 hours. We checked that 8 computers failed. From this 8, there were 4 that failed after 1.200 hours, then 2 of them failed after 1.800 hours and the last 2 failed after 2.400 hours. Calculate the reliability, the percentage of failures, the number of failures and the mean time between failures.
In an industry plant, they are evaluating 500 units of an electronic component that were working 10 hours. On the final report, we could read that the reliability is really high. And we could see the following information. Mean time beetwen failures 20 hours. Number of components that failed 20. Please calculate the reliability.
The reliability analysis of a bike carried out during 2.000 hours (total time), has concluded that from 1000 units, only 20 have failed. Choose the correct answer: a. The reliability is 98% b. If the non operation time is 20h, we obtain 0,01 failures per hour. c. If the operation time is 1980 hour, we obtain 10 failures per 1000 hours working. d. All the answers are correct.
A manufacturer of disk drives or notebook computers wants a Mean time between failures of at least 50.000 hours. Recent test results for 10 units were on failure at 10.000 hours, another at 25.000 hours and two more at 45.000 hours. The remaining units were still running at 60.000 hours. Determine the percent of failures, the number of failures per unit- hour and MTBF at this point in the testing.
A Light bulb producer tell us that the reliability is 99,99%. A) What does it mean? After checking them we realize that between 100.000 bulbs (working 1.000 hours) only 900 bulbs failed. B) Could we still saying that the reliability is 99,99%? After checking it, the mean time between failures was 24 hours. C) Calculate the number of failures per operation time.
In an assembly chain we have 3 “stops” per week. The chain works 24 hours per day but only 5 days per week. In order to restart the chain it is necessary to spend a mean time of 30 minutes. They want to hire a new specialist in order to reduce the restarting time of the machinery. This specialist tell us that with his advice the machinery will achieve a reliability of 99,95%. Should we accept his offer?
The failure rate is 5%. Choose the correct answer: a. The reliability is higher than 100% b. If they have produced 110 units, 5 have failed c. The reliability is 95% d. None of them are correct.

LESSON 2 EXERCISES Reliability