Maintainability

Question 1

“The propability that a failed system will be restored to an operational condition with a specified time” is a definition of:

Answer 1

Repairability (IX - 2/3)

Question 2

Reliability active time includes what two major components?

Answer 2

Up time and down time (IX - 4)

Question 3

An appropriate preventive maintenance programm can greatly increase the overall availability of a system because of:

Answer 3

An increase in observed reliability (IX - 6/11)

Question 4

The “gold in the mine” for repairability and maintainability is:

Answer 4

The savings on maintenance and logistics (IX - 37)

Question 5

A designer`s responsibility is to include maintenance considerations in any design. The considerations should include:

Answer 5

Reduction and ease of maintenance (IX - 2 and 37)

Question 6

In a total productive maintenance (TPM) environment, the operator is trained to handle small and routine repairs
to the equipment (use of autonomous group activities). Skilled maintenance craftman are still required for the heavy duty, specialized areas of repair and restoration.

Answer 6

The equipment operators perform routine equipment maintenance (IX - 11)

Question 7

The optimum parts replacement policy that attempts to determine the replacement age therby minimizing the downtime per unit of time is called:

Answer 7

Preventive replacement at predetermined age (IX - 19)

Question 8

A preventive maintenance program that follows the philosophy of optimum parts replacement will have:

Answer 8

Some failures (IX - 15/21)

Question 9

What kind of failure would most likely result fom insufficient hardware debugging?

Answer 9

Early failure ( IX - 7)

Question 10

Which of the following is the reason the bathtub curve has an increasing failure rate during wear-out period?

Answer 10

Design, materials and environment determine a limit of useful life (IX - 34/35)

Question 11

Preventive maintenance can be justified as cost effective when:

Answer 11

The corrective maintenance cost can be significantly reduced (IX - 32/38)

Question 12

What is System Effectiveness, if Operational Readiness is 0.89, Design Adequacy is 0.95, Availability is 0.98, Maintainability is 0.93 and Mission Reliability is 0.99?

Answer 12

System Effictivfeness = Mission Reliability x Operational Readiness x Design Adequacy (IX - 3 ; 0.837)

Question 13

Maintainability is the propability of:

Answer 13

An item to be retained or restored to a specific condition for a specified mission (IX - 10/12)

Question 14

Historical data has shown for a particular electronic component that it experiences infant mortality and then a constant failure rate thereafter. For this component:

Answer 14

Performing preventive maintenance increases the failure rate (IX - 7)

Question 15

The optimum time between maintenance actions is:

Answer 15

Found by minimizing the total cost per unit time (IX - 19)

Question 16

What would be the spares required for 100 units at a failure rate of 2000 x 10^-9 failures per operation hours? The operating time is 4000 hours. The level of confidence is 0.95.

Answer 16

a) calculate => Spares/unit = lambda * t + Z √ lambda * t

b) For 100 units, spares = 100 * # Spares/unit ( IX - 25)

Question 17

It is often observed that unscheduled maintenance:

Answer 17

Does not necessarily isolate failure causes (IX - 36

Question 18

In consideration of the life histroy curves of complex products

a reliability centered maintenance approach would indicate that …

Answer 18

Some items are better left alone

(IX - 7)

Question 19

Given a Weibull failure distribution for an extruder producing packaging film with g =400 hours, b=1.5, h=700 hours. The cost of a scheduled PM action is $5,000, while the cost of an unexpected failure is $15,000. The line operates as 8,760 hours per year and scheduled PM is now set at every quarter. Determine the approximate costs for the existing PM schedule.

Answer 19

C = PM Cost + Failure Cost (IX - 18)

Question 20

High cycle fatigue would most likely result in:

Answer 20

Wear out failure (IX - 7)

Question 21

The objective of using a constant interval replacement policy is to:

Answer 21

Minimize the total downtime and to minimize the unavailability of the equipment (IX - 19)

Question 22

If a component experiences infant mortality but does not experience aging during its life then:

Answer 22

A system overhaul leads to additional infant mortality possilbilities (IX - 7)

Question 23

A total productive maintenance is a program in which:

Answer 23

Equipment maintenance is shared between operators and maintenance personnel (IX - 10/11)

Question 24

The maintenance time needed to replenish consumables and check out an item for recommitment is called;

Answer 24

Turn around time

IX - 5

Question 25

The basic maintainability requirements for a system or component are best determined via:

Answer 25

Analysis of customer requirements (IX - 2/3)

Question 26

Preventive maintenance policies are best applied when:

Answer 26

The system has an increasing hazard rate (IX - 7 and 35)

Question 27

If the assumption is met that a repairable system has a constant failure rate while up and repair restores the system to its previous failure rate, which of the following implications it true?

Answer 27

Burn-in would not be effective (IX - 34/35)

Question 28

Fault isolation is rarely facilitated by using which of the following?

Answer 28

Corrective maintenance (IX - 32/33 and 37/38)

Question 29

The effectiveness of a maintenance program is affected most by:

Answer 29

Designed ease of installation and removal of components (IX - 36/38)

Question 30

When forecasting needed spares based on field data, what is the formula for total wait time?

Answer 30

1 / rapair rate - failure rate (IX - 30)

Question 31

The maintenance time constraint (t) is:

Answer 31

Usually prescribed as a requirement of the mission (IX - 2/5)

Question 32

A project engineering team did a good job of building a plant in modules and standardizing as much as possible. There was high inherent reliability in the installed equipment and machinery. The maintenance department demand for repair and replacement parts was very low for the past year. During the next few months there is a big spice in replacement parts. This can be explained as:

Answer 32

WEAP (Warranty expiration anticipation phenomenon)

The part to be replaced has not worn out as of yet but the warranty is due to expire and good practice might dictate that parts be changed out on scheduled even if not needed. This would cause the spice ( IX - 21)

Question 33

In order to sustain a high system reliability in the field it is best to:

Answer 33

Follow a preventive maintenance program with scheduled diagnostic checks (IX - 32/38)

Question 34

The following information pertains to a wheel hub that has five bolts.

• The unreliability of each bolt is 0.001
• Four wheel bolts are adequat to perform the designed function
• Failures are independent

What is the reliability of the system?

Answer 34

Binominal table for p=.005 ; n=5 ; r=1 or

Question 35

The average rate for patient arrival at a hospital is 2 patients per hour. If the arrival rate follows a Poisson distribution, what is the propability of exactly 2 patients arriving in one hour?

Answer 35

1) look up in Poisson table
2) It is equal to the propability of exactly 1 patient arriving

np = 2 ; r = 2 = 0.2707 / r = 1 = 0.2707

Question 36

A fault tree analysis (FTA) uses which of the following elements to determine the propability of a predetermined event occuring?

Answer 36

Boolean algebra

Question 37

A component has a Weibull failure distribution with a shape parameter of 0.8 and scale parameter of 300 hours.

Scheduling replacement every 200 hours will result in which of the following outcomes?

Answer 37

Descreased failure rate

Question 38

The reliability centered maintenance (RCM) approach has potential for use in many areas of industry, having been
successfully emplayed in the aircraft and nuclear power industries. A major premise of RCM is which of the following?

Answer 38

Preserve system function (IC - 6/9)

Question 39

What would be the spares required for 100 units at a failure rate of 2000 x 10^-9 failures per operation hours? The operating time is 4000 hours. The level of confidence is 95%.

Answer 39

Spares/unit = lambda t + Z √ lambda t (IX-25 ; 15,5 spares)

Question 40

High cycle fatigue would most likely result in:

Answer 40

Wear out failure (IX-7)

Question 41

Total productive maintenance seeks to eliminate the “six big losses.”

Which is included in the downtime category?

Answer 41

Setup losses

Question 42

What is the first step when conducting a maintainability study for a piece of existing equipment?

Answer 42

Identifying the problems that are causing the majority of downtime

Question 43

The result of a maintainability analysis should include:

Answer 43

The support equipment and tools required