Question 1

A job consists of a series of three tasks. Task 1 is performed correctly 98% of the time, task 2 is performed correctly 99% of the time, and task 3 is performed correctly 97% of the time. The reliability of this job is

Accepted Answer

The reliability of the job can be calculated by multiplying the individual probabilities of each task being performed correctly: 0.98 x 0.99 x 0.97 = 0.9411 or 94.11%. Therefore, the best choice is B.

Question 2

The objective of maintenance and reliability is to

Accepted Answer

The objective of maintenance and reliability is to maintain the capability of the system, which includes ensuring that breakdowns are minimized through preventive maintenance, and that the system is reliable and available when needed. The other choices either are unrealistic or do not address the main objective of maintenance and reliability.

Question 3

TPM (total productive maintenance) is an application of TQM (total quality management) principles to the area of maintenance.

Accepted Answer

TPM focuses on maximizing equipment effectiveness and minimizing downtime through a focus on maintenance of equipment and involvement of all employees, which is aligned with TQM principles of continuous improvement, involvement of all employees, and customer satisfaction.

Question 4

A product has three components, A, B, and C, with reliabilities of 0.95, 0.98, and 0.995. Engineers intend to put a redundant component A that has reliability 0.70. With this change, system reliability will

Accepted Answer

To find the new reliability, we need to use the formula for parallel components:
R_total = 1 - (1 - R_A)(1 - R_B)(1 - R_C)
where R_total is the reliability of the system with the redundant component A and R_A, R_B, and R_C are the reliabilities of components A (redundant), B, and C, respectively.

Substituting the given values, we get:
R_total = 1 - (1 - 0.70)(1 - 0.98)(1 - 0.995)
R_total = 0.99916

Therefore, the system reliability will rise to 0.99916, which is higher than the original reliability of 0.95. Therefore, the answer is C) rise.

Question 5

Which of the following best illustrates the importance of employee involvement in achieving successful maintenance and reliability?

Accepted Answer

Employee involvement is key to successful maintenance and reliability. This is highlighted by the fact that employee involvement through reward systems and power sharing, combined with good maintenance and reliability procedures, can improve capacity and reduce variability. This emphasizes the importance of not only having effective maintenance and reliability procedures but also engaging and empowering employees to participate in the process.

Question 6

What is the reliability of a four-component product, with components in series, and component reliabilities of .90, .95, .98, and .99?

Accepted Answer

The reliability of a series system is the product of the reliabilities of its components: 0.90 * 0.95 * 0.98 * 0.99 = 0.8322, which is under 0.83.

Question 7

A system has three components in parallel with reliabilities 0.9, 0.7, and 0.5. System reliability is

Accepted Answer

The reliability of the system in parallel is calculated as 
Rsystem = 1 - (1-R1)*(1-R2)*(1-R3), where R1, R2, R3 are the reliabilities of the individual components. 
Plugging in the values, we get 
Rsystem = 1 - (1-0.9)*(1-0.7)*(1-0.5) = 0.985.
Therefore, the best choice is D.

Question 8

The probability that a product will function properly for a specified time under stated conditions is

Accepted Answer

The probability of a product functioning properly for a specified time under stated conditions is referred to as reliability.

Question 9

An optimal maintenance policy strikes a balance between the costs of breakdown and preventive maintenance so that the total cost of maintenance is at a minimum.

Accepted Answer

This statement is true. Optimal maintenance aims to minimize the total cost of maintenance, which includes the costs of both breakdown and preventive maintenance. The right balance between these two types of maintenance will result in the lowest overall cost.

Question 10

Which of the following statements about maintenance at Orlando Utilities Commission is False?

Accepted Answer

The statement that each power-generating unit is taken off-line for maintenance every one to three weeks is false. It contradicts the statement in (A) that a less frequent overhaul schedule is used for preventive maintenance.

Question 11

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

Accepted Answer

When components are connected in a series, the failure of any single component can cause the entire system to fail. Therefore, as the number of components in a series decreases, the likelihood of any one component failing and causing the system to fail also decreases, leading to increased reliability.

Question 12

Which of the following is a reliability tactic?

Accepted Answer

Improving individual components and providing redundancy are both reliability tactics. Increasing repair speed may improve availability, but it is not directly related to reliability. Therefore, the best choice is D.

Question 13

The objective of maintenance and reliability is to maintain the capability of the system.

Accepted Answer

The objective of maintenance and reliability is to maintain the capability of the system, which includes its availability, performance, and safety. This is achieved by optimizing maintenance activities, improving equipment reliability, and preventing failures. By maintaining the capability of the system, organizations can ensure that they can meet their operational objectives in a safe, reliable, and cost-effective manner.

Question 14

A system is composed of three components A, B, and C. All three must function for the system to function. There are currently no backups in place. The system has a reliability of 0.966. If a backup is installed for component A, the new system reliability will be

Accepted Answer

Since all three components must function for the system to function, the system reliability is the product of the individual reliabilities: R = R(A)*R(B)*R(C). 
Given that the initial reliability of the system without a backup is 0.966, we can solve for the individual reliabilities as follows:

0.966 = R(A)*R(B)*R(C)

Since all three components are necessary, each one has a reliability of R(C) = 0.966^(1/3) ≈ 0.988. 
If a backup is installed for component A, the new reliability of that component is greater than 0.966. Let's assume its new reliability is R(A)' = 0.99. Then the new system reliability would be:

R' = R(A)'*R(B)*R(C) = 0.99*1*0.988^2 ≈ 0.977

Therefore, the answer is D) greater than 0.966.

Question 15

Components A, B, and C are connected in series. Component D is connected in parallel to component B. Which of the following statements is true?

Accepted Answer

Components A, B, and C are connected in series, which means that all three components must work in order for the system to work. However, component D is connected in parallel to component B, which means that if either B or D works, the system can still work. Therefore, the system works when A works, C works, and either B or D works.

Question 16

What is the reliability of the three components connected in series shown below?

Accepted Answer

The answer of What is the reliability of the three...

Question 17

Simulation models and expert systems are useful tools for enhancing maintenance.

Accepted Answer

Simulation models and expert systems can help in predicting equipment failures, optimizing maintenance schedules, and providing automated diagnostic and decision-making support. Therefore, they can be useful tools for enhancing maintenance.

Question 18

While breakdowns occur randomly, their frequency is somewhat predictable through such tools as the product failure rate, MTBF, and the breakdown costs model.

Accepted Answer

The statement is true. These tools can help companies plan and prepare for breakdowns by predicting their frequency and associated costs.

Question 19

A system has three components in series with reliabilities 0.9, 0.7, and 0.5. System reliability is

Accepted Answer

The reliability of a series system is the product of the reliabilities of its components. Thus, the system reliability is 0.9 * 0.7 * 0.5 = 0.315.

Question 20

Consider a product with three components in series, with reliabilities of 0.90, 0.80, and 0.99 for components A, B, and C, respectively. Furthermore, component B uses a backup that also has a reliability of 0.80. What is the reliability of the system?

Accepted Answer

To find the overall reliability of the system, we need to use the formula for series-parallel systems:

R_sys = R_A × R_AB × (R_B + R_BC − R_B × R_BC)

where R_AB is the reliability of the backup used for component B. Plugging in the given values, we get:

R_sys = 0.90 × 0.80 × (0.80 + 0.99 − 0.80 × 0.99) = 0.85536

Therefore, the reliability of the system is 0.85536 or approximately 85.54%, which is closest to choice D.

Quiz 20: Maintenance and Reliability