System Reliability &Amp; Plant Maintenance Question Paper

System Reliability &Amp; Plant Maintenance

Course:Bachelor Of Science In Renewable Energy Technology And Management

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE (ENERGY ENGINEERING)

SET 500: SYSTEM RELIABILITY & PLANT MAINTENANCE

DATE: Tuesday 22nd December 2009
TIME: 11.00am – 1.00pm

INSTRUCTIONS
Answer any Three Questions
QUESTION ONE
a)
i)
With suitable examples, differentiate between passive and partially loaded
redundancies.
[7marks]

ii)
Sketch a standby system with n units and state its assumption.

[3marks]
b)
Consider the standby system sketched in figure (ii). Assuming that the system

consists of identical units with constant failure rate, ? . The probability that
switch
s will fail to activate the standby unit is p. Perform the following
operations.

i)
Determine an equation of survivor function of the unit system at time t.
and
state
necessary
assumptions/s.
ii)
If
p = 1.5%, ? =10-3 and t = 1000hrs, what is the probability that this
system
survives
1000hrs?
[10marks]

Page 1 of 3
QUESTION TWO
a) i) Discuss
the
procedure
of obtaining the expression:

p (t < T = t + ? t /T > t)
=
Z (t) . t
?
in
systems
reliability.
[7marks]

ii)
How do you measure reliability of an unrepaired unit.
[3marks]
b)
i)
What is the significance of Z[t]. ? t is the equation shown (a) (i).

[5marks]

ii)
A parallel system consists of 3 components A, B, and C. If the reliabilities

of the three components are RA = 0.81, RB = 0.85 and RC = 0.78.
Find
the
system
reliability.
[5marks]

QUESTION THREE
a)
i)
What
is
bathtub
curve. [3marks]

ii)
Discuss the failure rate of a unit that is not repaired.
[7marks]
b)
You’re given a system consisting of four components C1 C2 C3 and C4 as

shown in figure Q3.

i)
If the four components correspond to fur switches, explore all the
conditions
of

the
switches and the system.

[5marks]

ii)
Determine the system reliability if the components reliabilities are:

R1 = 0.9 R2 = 0.8, R3 = 0.7 and R4 = 0.6.

Fig.
Q3

[5marks]

QUESTION FOUR
a)
i)
What is the importance of conducting reliability tests during design,
construction
and
operating
stages.
[5marks]
ii)
Discuss
the
following
reliability that methods.
a)
Sudden
Death
Testing
Page 2 of 3
b)
Sequential
Life
Testing.
[5marks]
b)
i)
What
is
reliability
margin?
[6marks]

ii)
The failure times of Teri automobile brakes are observed to be 4350, 5200,

6350, 7200, 8450, 9350, 10100, 11150, 116000 and 12350 Kilometeres of

operation. Determine and plot the following parameters’
a)
Probability
density.
[2marks]

b)
Probability
distribution [2marks]
c)
Reliability
and
[2marks]

d)
Hazard function of the failure of the brakes’
[2marks]

QUESTION FIVE
a)
i)
Compare and/contrast the following terms.
i)
Availability
and
maintainability
ii)
Safety
and
security.
[4marks]

ii)
Discuss the importance of system reliability technology.

[6marks]
b i)
What
is
the
maintenance?
[2marks]

ii)
Find the reliability of co system for which preventive maintenance is

performs after every 500 hours of operation when the failure time T in

hours, of the original system is given by the following distributions
1
?
? 1 ? + -1000 ?2??

f (t) =
exp
- ?
?
[9marks]
T
?
?
2p 50
( )
? 2 ?
50
? ?
?
?

Page 3 of 3

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