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Exam 20: Maintenance and Reliability

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Question 61

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As the number of components in a system connected in a series decreases, all other things being equal, the reliability of the system usually

A) increases
B) stays the same
C) decreases
D) increases, then decreases
E) decreases, then increases

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Question 62

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__________ is the failure rate early in the life of a product or process.

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Question 63

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What is breakdown maintenance?

A manager is comparing the total maintenance (preventive plus breakdown) cost curves for two scenarios. The graphs have maintenance commitment on the x-axis and costs on the y-axis. Scenario A includes the direct breakdown maintenance costs, while Scenario B includes the "full" (direct and indirect) breakdown maintenance costs. Which of the following should the manager notice when going from Scenario A to Scenario B?

Ten high-technology batteries are tested for 200 hours each. One failed at 20 hours; another failed at 140 hours; all others completed the test. FR(%) is __________ and MTBF is __________.

Ten high-intensity bulbs are tested for 100 hours each. One failed at 40 hours; all others completed the test. Calculate FR(%) and FR(N).

Which product design below has the higher system reliability?

Ten high-technology batteries are tested for 200 hours each. One failed at 50 hours; all others completed the test. FR(%) is __________ and FR(N) is __________.

An oil change is to ____________ maintenance as repair of a broken alternator is to ____________ maintenance.

__________ is the expected time between a repair and the next failure of a component, machine, process, or product.

The MTBF distributions of products, machines, or processes that have "settled in," or gone beyond the infant mortality phase, often follow the normal distribution.

Why is it that many cost curves associated with maintenance rarely consider the full cost of a breakdown?

Identify the two reliability tactics and the two maintenance tactics.

Which of the following is a reliability tactic?

Small standard deviations in the MTBF distribution of a machine tend to support a policy of breakdown maintenance for that machine.

Is there an optimal amount of preventive maintenance? What caution should be exercised before calculating this optimal amount?

Suppose that a car mechanic offers you a deal that for the next 3 years any breakdowns will be covered, so long as you bring your car in for $50 preventative maintenance sessions each month. If you predict the likelihood of a breakdown being 25% without the maintenance, how much must a breakdown cost for you to prefer the preventative maintenance?

Which of the following increase as repairs move from the maintenance department to the depot service?

A product is composed of a series connection of four components with the following reliabilities. What is the reliability of the system? $\begin{array}{|l|c|c|c|c|}\hline\text { Component } & 1 & 2 & 3 & 4 \\\hline \text { Reliability } & .90 & .95 & .97 & .88 \\\hline\end{array}$

Consider a product that is "settled in." Its MTBF distribution has been found to be normal with a mean of 1,000 hours and a standard deviation of 250 hours. What is the probability of a breakdown before 750 hours? Before 500 hours? Would you prefer a policy of preventive maintenance, or a policy of breakdown maintenance, on this product? Explain your choice.