46) A product has four components A, B, C, and D. The finished product must have a reliability of at least
.95. The first three components come from a supplier, and they have reliabilities of .99, .98, and .995,
respectively. The fourth component is being designed now. What must the reliability of component D be
in order to meet the product reliability condition?
47) A product has three components X, Y, and Z. Product X has reliability of 0.991, and Y has reliability of
0.993. If Z has reliability of 0.991, what is the reliability of the entire product? Can Z be redesigned to be
reliable enough for the entire product to have reliability of 0.99? Explain.
48) A component must have reliability of .9925. Two technologies are available for this component: one
produces a component with .999 reliability at a cost of $2000. Another produces a component with .73
reliability at a cost of $450. Which is cheaper: one high quality component or a parallel set of inferior
components? (Hint: for the inferior components, you first need to determine the number of them that
would be needed to ensure overall reliability of .9925.)
49) General Grant must send orders to General Butler. Carrier pigeons are the medium of choice. A single
pigeon has a .7 probability of arriving at the proper destination in a timely fashion. How many pigeons,
each carrying an identical set of orders, must Grant send in order for him to have 98% confidence that the
orders reached General Butler?
50) Suppose that a three-stage process had reliability ratings of .7, .8, and .9 at each station and that a
failure at any station represented a failure for the entire process. If each station is given a redundant
check with .9 reliability, what is the increase in system reliability?
51) Suppose that a three-stage process in a nuclear reactor had reliability ratings of .98 at each station and
that only one stage needed to be successful for the process to work. If the plant wants to establish 6-sigma
standards (≤ 3.4 defects per million), what % reliable redundant controls need to be added to each station.
Section 3 Maintenance
1) Preventive maintenance is reactive.
2) Preventive maintenance is nothing more than keeping the equipment and machinery running.
3) Preventive maintenance implies that we can determine when a system needs service or will need
repair.
4) Infant mortality refers to the high failure rate often encountered in the very early stages of the lifetime
of a product.
5) The MTBF distributions of products, machines, or processes that have “settled in,” or gone beyond the
infant mortality phase, often follow the normal distribution.
6) Recording the maintenance history of processes, machines, or equipment is important for preventive
maintenance, but largely irrelevant for breakdown maintenance.
7) The “full cost view of maintenance” results in more firms choosing a policy of breakdown maintenance,
when compared to the “traditional view of maintenance.“
8) Small standard deviations in the MTBF distribution of a machine tend to support a policy of
breakdown maintenance for that machine.
9) When identifying the optimal maintenance policy, the cost of inventory maintained to compensate for
the downtime is a cost often ignored.
10) 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.
11) While breakdowns occur randomly, their frequency is somewhat predictable through such tools as
the product failure rate, MTBF, and the breakdown costs model.
12) The normal distribution is an appropriate model of:
A) the high initial failure rates of product, machine, or processes.
B) system reliability where components are connected in series.
C) system reliability where components are connected in parallel.
D) the MTBF distribution of products, machines, or processes that have “settled in.”
E) the full cost view of maintenance.
13) Infant mortality refers to which one of the following examples?
A) high frequency on the left side of the MTBF distribution
B) failure of items used in the nursery ward of a hospital
C) failure of products with a very short life cycle
D) market failure of brand new products
E) high failure rate often encountered in the very early stages of the lifetime of a product
14) Which one of the following statements about maintenance is TRUE?
A) The optimal degree of preventive maintenance is associated with zero breakdowns.
B) Breakdown maintenance is proactive.
C) Preventive maintenance is reactive.
D) Preventive maintenance is for emergency repairs.
E) Human resources are a major component of effective maintenance management.
15) What is the process that involves repair on an emergency or priority basis?
A) breakdown maintenance
B) emergency maintenance
C) failure maintenance
D) preventive maintenance
E) priority maintenance
16) As a firm’s maintenance commitment increases:
A) the breakdown maintenance costs increase, and the preventive maintenance costs decrease.
B) both the breakdown maintenance costs and the preventive maintenance costs decrease.
C) the breakdown maintenance costs decrease, and the preventive maintenance costs increase.
D) both the breakdown maintenance costs and the preventive maintenance costs increase.
E) None of the above is true.
17) An oil change is to ________ maintenance as repair of a broken alternator is to ________ maintenance.
A) preventive; breakdown
B) breakdown; preventive
C) preventive; preventive
D) breakdown; breakdown
E) preventive; infant mortality
18) Suppose that the introduction of a preventive maintenance program is deemed cost effective. Which
of the following is most likely true if the cost to actually perform preventive maintenance is very
expensive?
A) high standard deviation in MTBF
B) low standard deviation in MTBF
C) low cost to repair
D) Repairs carry little non-monetary consequences.
E) The system never fails.
19) 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?
A) Total cost is decreased.
B) Optimal point is moved to the left.
C) Optimal point is moved to the right.
D) Preventative maintenance cost slope is increased.
E) None of the above
20) As far as maintenance costs are concerned:
A) for low levels of maintenance commitment, breakdown maintenance costs exceed preventive
maintenance costs.
B) for low levels of maintenance commitment, preventive maintenance costs exceed breakdown
maintenance costs.
C) for high levels of maintenance commitment, breakdown maintenance costs exceed preventive
maintenance costs.
D) preventive maintenance is always more economical than breakdown maintenance.
E) breakdown maintenance is always more economical than preventive maintenance when the “full cost
of breakdowns” is taken into consideration.
21) Which one of the following is NOT necessary to identify the optimal maintenance policy?
A) historical data on maintenance costs
B) cost of performing the analysis
C) breakdown probabilities
D) breakdown occurrences
E) repair times
22) DuLarge Marine manufactures diesel engines for shrimp trawlers and other small commercial boats.
One of their CNC machines has caused several problems. Over the past 30 weeks, the machine has
broken down as indicated below.
Number of breakdowns per week
0
1
2
3
4
Frequency (Number of weeks that breakdowns
occurred)
8
3
5
9
5
What is the expected number of breakdowns per week?
A) 1
B) 2
C) 6
D) 10
E) 30
23) DuLarge Marine manufactures diesel engines for shrimp trawlers and other small commercial boats.
One of their CNC machines has caused several problems. Over the past 30 weeks, the machine has
broken down as indicated below. Each time the machine breaks down, the firm loses an average of $3,000
in time and repair expenses.
Number of breakdowns per week
0
1
2
3
4
Frequency (Number of weeks that breakdowns
occurred)
8
3
5
9
5
What is the expected breakdown cost per week?
A) $1,000
B) $2,000
C) $6,000
D) $10,000
E) $60,000
24) DuLarge Marine manufactures diesel engines for shrimp trawlers and other small commercial boats.
One of their CNC machines has caused several problems. Over the past 30 weeks, the machine has
broken down as indicated below. Each time the machine breaks down, the firm loses an average of $3,000
in time and repair expenses. If preventive maintenance were implemented, it is estimated that an average
of only one breakdown per week would occur. The cost of preventive maintenance is $1,000 per week.
Number of breakdowns per week
0
1
2
3
4
Frequency (Number of weeks that breakdowns
occurred)
8
3
5
9
5
What is the weekly total maintenance cost of this program?
A) $1,000
B) $3,000
C) $4,000
D) $6,000
E) $8,000
25) When depot service is compared to operator maintenance:
A) operator maintenance is slower than depot service.
B) competence is higher, but costs may also be higher, with depot service.
C) depot service is often the weak link in the chain because of the lack of specific training.
D) depot service occurs on-site, while operator maintenance occurs off-site.
E) depot service is better for systems connected in parallel, while operator maintenance is preferred for
systems connected in series.
26) Which of the following increases as repairs move from the maintenance department to the depot
service?
A) cost
B) replacement time
C) competence
D) operator ownership
E) A, B, and C
27) Autonomous maintenance occurs when:
A) employees are empowered to observe, check, adjust, clean, and notify.
B) a remote computer system signals the need for breakdown maintenance.
C) a remote computer system signals the need for preventative maintenance.
D) employees perform their own breakdown maintenance.
E) none of the above
28) ________ is a plan that involves routine inspections, servicing, and keeping facilities in good repair to
prevent failure.
29) ________ is the failure rate early in the life of a product or process.
30) The ________ takes into account such costs as deteriorated customer relations and lost sales.
31) Why is it that many cases of infant mortality of products are not due to product failure?
32) What is breakdown maintenance?
33) Explain why a small standard deviation of the MTBF distribution makes a product, machine, or
process a good candidate for preventive maintenance while a large standard deviation does not.
34) Why is it that many cost curves associated with maintenance rarely consider the full cost of a
breakdown?
35) Is there an optimal amount of preventive maintenance? What caution should be exercised before
calculating this optimal amount?
36) How do many electronic firms deal with infant mortality in their products?
37) Given the following data, find the expected breakdown cost. The cost per breakdown is $200.
Number of breakdowns per week
0
1
2
3
4
Weekly frequency
5
12
10
18
5
Number of breakdowns per week
0
1
2
3
4
Weekly Probability
1.00
38) Given the following data, find the expected breakdown cost. The cost per breakdown is $100.
Number of breakdowns
0
1
2
3
Monthly frequency
5
20
23
2
Number of breakdowns
0
1
2
3
Monthly probability
39) Great Southern Consultants Group’s computer system has been down several times over the past few
months, as shown below.
Number of breakdowns
0
1
2
3
4
Monthly frequency
9
2
4
4
1
Each time the system is down, the firm loses an average of $400 in time and service expenses. They are
considering signing a contract for preventive maintenance. With preventive maintenance, the system
would be down on average only 0.5 per month. The monthly cost of preventive maintenance would be
$200 a month. Which is cheaper, breakdown or preventive maintenance?
Number of breakdowns
0
1
2
3
4
Monthly probability
40) Tiger Island Fabricators, which builds offshore oil platforms, has been experiencing problems with its
profiling machine, a computer-driven device that cuts the ends of pipe so that it can be welded to another
pipe, as shown in the data below.
Number of breakdowns
0
1
2
3
4
5
Breakdown frequency
2
2
2
6
7
1
Each time a machine breaks down, the company loses about $3,000. If the company implements
preventive maintenance, it will be able to reduce the number of breakdowns to one per month.
Preventive maintenance costs would be $500 a month. Is preventive maintenance a cost-effective option?
0
1
2
3
4
5
Section 4 Total Productive Maintenance
1) TPM (total productive maintenance) is an application of TQM (total quality management) principles to
the area of maintenance.
2) Simulation models and expert systems are useful tools for improving total productive maintenance.
3) Which of the following is true regarding total productive maintenance (TPM)?
A) TPM is concerned with machine operation, not machine design.
B) Field service and depot service perform virtually all maintenance and repair activities.
C) Operators run their machines, but maintenance departments maintain them.
D) TPM reduces variability through autonomous maintenance and excellent maintenance practices.
E) TPM views maintenance and repair as tactical issues, not strategic ones.
4) Techniques for improving total productive maintenance can include which of the following?
A) simulation
B) expert systems
C) sensors
D) A and C
E) A, B, and C
5) ________ combines total quality management with a strategic view of maintenance from process
equipment design to preventive maintenance.
6) What is the primary concept of total productive maintenance (TPM)? Identify the four elements that
productive maintenance includes.