TUTORIAL: RELIABILITY MODELS Course Title: QUALITY MANAGEMENT Instructor(s): Dr. BELKACEM ATHAMENA Dellana Company tested 50 products for 75 hours each. During this time, it experienced four breakdowns. Compute the number of failures per hour. What is the mean time between failures? Exercise 2: Collier Company tested 200 products for 100 hours each. During this time, it experienced 12 breakdowns. Compute the number of failures per hour. What is the MTBF? Exercise 3: Crager Company tested 100 products for 50 hours each. During the test, three breakdowns occurred. Compute the number of failures per hour and MTBF. Exercise 4:
Exercise 1:
TUTORIAL: RELIABILITY MODELS Course Title: QUALITY MANAGEMENT
Instructor(s): Dr. BELKACEM ATHAMENA
Dellana Company tested 50 products for 75 hours each. During this time, it experienced four breakdowns. Compute the number of failures per hour. What is the mean time between failures?
Exercise 2:
Collier Company tested 200 products for 100 hours each. During this time, it experienced 12 breakdowns. Compute the number of failures per hour. What is the MTBF?
Exercise 3:
Crager Company tested 100 products for 50 hours each. During the test, three breakdowns occurred. Compute the number of failures per hour and MTBF.
Exercise 4:
Suppose that a product is designed to function for 10,000 hours with a 3% chance of failure. Find the average number of failures per hour and the MTTF.
Exercise 5:
Suppose that a product is designed to function for 100,000 hours with a 1% chance of failure and suppose that six of them are in use at a facility. Find the average number of failures per hour and the MTTF.
Exercise 6:
Suppose that there are 42 pumps used in a refinery that are continuously being used with a 2% chance of failure over 50,000 hours. If the repair time is 10 hours to install a new rebuilt pump, how many pumps should be kept on hand to keep the chance of a plant
shutdown to less than 1% (Hint: Treat this problem as a traditional safety stock problem and use a z table.)
Exercise 7:
Suppose that a product is designed to work for 1,000 hours with a 2% chance of failure. Find the average number of failures per hour and the MTTF.
Exercise 8:
A product has been used for 5,000 hours with 1 failure. Find the mean time between failures (MTBF) and λ.
Exercise 9:
You have to decide between three potential suppliers for an assembly for a product you are designing. After performing life testing on several assemblies, you find the following:
Supplier MTBF (hr) MTTR (hr) 1 45 2
2 90 2
3 120 6
4 200 6
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