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Set 500: Systems Reliability And Plant Maintenance Engineering Question Paper
Set 500: Systems Reliability And Plant Maintenance Engineering
Course:Alternative Dispute Resolution
Institution: Kenyatta University question papers
Exam Year:2008
KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2008/2009
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE IN MANUFACTURING ENGINEERING
SET 500: SYSTEMS RELIABILITY AND PLANT MAINTENANCE
ENGINEERING
DATE: Tuesday 25th November, 2008 TIME: 11.00 a.m. – 1.00 p.m.
INSTRUCTIONS
This paper contains FIVE questions.
Answer any THREE.
Figures for Q2(a) and Q2(b) are attached at the back.
1. (a) (i) How is reliability of an unrepaired unit measured?
[6 marks]
(ii) Differentiate between the following terms:
(i) Survivor function and probability of failure in time (0,t)
(ii) Time to failure and Failure rate. [4 marks]
(b) With suitable illustrations show the correlation between the probability of
a unit failing within time interval (0,t) and probability density.
[10 marks]
2. (a) A system consist of components CA, CB, CC, CD, and CE connected in
series and in parallel as shown in the figures Q2 below. The reliabilities
of the components are RA = 0.99, RB = 0.9, RC = 0.8, RD = 0.7 and
RE = 0.99.
Find the system reliability.
Figure Q2(a): System connection attached. [8 marks]
2
(b) (i) With relevant assumptions sketch a standby system with n units
and show how to determine the life time of the system.
[7 marks]
(ii) Consider the standby system figure Q2(b). Assuming that it
compost of two (n = 2) identical pumps each with constant failure
rate ? = 10-3 failure/hour. The probability ? that the main switch
will fail to activate (switch over and start) the standby pump has
been estimated to 1.5%.
Determine:
(i) the survivor function.
(ii) The mean time to system failure.
Figure Q2(b) Standby System attached. [5 marks]
3. (a) Justify the importance of conducting reliability tests at various stages of
the life cycle of a system [9 marks]
(b) The failure times of ten automobile brakes are observed to be 43500,
52000, 63500, 72000, 84500, 93500, 101000, 111500, 116000 and 123500
kilometres of operation. Plot the probability density, probability
distribution and reliability functions of the failure time of the brakes.
[11 marks]
4. (a) List four assumptions for development of a model for availability analysis
of a system. [4 marks]
(b) (i) Sketch a transition diagram for the states of a system (machine).
[3 marks]
5. (a) (I) Define the terms maintainability and availability. [2 marks]
(II) Differentiate between the following terms:
3
(i) Preventive and corrective maintenance
(ii) Inherent availability and achieved availability
[4 marks]
(b) The repair time ti for a mainframe computer system are observed to be 1.3,
1.5, 1.7, 1.8, 2.2, 2.6, 3.0, 3.1, 3.3 and 3.9 hours. Assuming lognormal distribution for the repair times, determine the following:
(i) Maintainability of the system for an allowed downtime of 5 hours. [10 marks]
(ii) Down-time required to achieve a maintainability of 0.99.
[4 marks]
………………
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