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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2009
Module Title: Maintenance & Reliability
Module Code: MANU
School: Mechanical and Process Engineering
Programme Title: Bachelor of Science (Honors) in Process Plant Technology / Bachelor of Science (Honours) in Advanced Manufacturing Technology
Programme Code: EPPTE_8_Y4, EAMTE_8_Y
External Examiner(s): Mr. Neil Kingson , Mr. Joe Phelan Internal Examiner(s): Mr. Jerry Larkin, Mr. Dan O’Brien
Instructions: Answer any 4 questions
Duration: 2 Hours
Sitting: Autumn 2009
Requirements for this examination: Probability Plotting Paper, Log Paper
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you are attempting the correct examination. If in doubt please contact an Invigilator.
Q. 1 Reliability Modelling Distributions:
(a) Produce a sketch of the bathtub curve identifying the three main failure rate regions.
(6 marks)
(b) The equipment in a packaging plant has a constant failure rate of 0.001/hr. What is
the probability of operating for a period of 450hrs without failure? (6 marks) Given: Exponential Distribution pdf
(c) Using the Decomposition Method, evaluate the system reliability for the system shown beneath in figure 1. (7 marks)
Verify your answer using the Cut Set method. (6 marks)
Given: Cut Set approximate reliability
Figur e 1. System Component Reliabilities
0.95 0.
f ( x )= e −^ = e − x x ≥
x
θ λ^ λ
=
n
i
RS Ri 1
Q. 3 Human Reliabilty
(a) Outline a framework for assessing Human Reliability. (10 marks)
(b) In the case of the Herald of Free Enterprise car ferry disaster the safety of the car ferry
depended on one member of the crew closing the bow doors before leaving harbor. There
was no check on this and it was assumed that the door would be close. This procedure
was carried out safely many times with no accident until disaster struck. The pertinent
facts were as follows.
- Due to the need for minimum turnaround time in harbor, the procedure of leaving the quayside before the bow loading door was shut was adopted.
- One member of the crew had to close the bow door before leaving harbor.
- Captains were aware of the risk and requested feedback to be provided on the bridge to show the door position. This fell on deaf ears and was refused by the board of directors.
- One day the person concerned was in his cabin and did not know that the ship had left the quayside. No one checked, and the Captain did not know. When the ship left the harbor, water entered through the bow door and the ship capsized with the loss of 188 lives.
Use the TESEO method to access operator risk ( TESEO error probabilities are presented in Table 4 )
(15 marks)
Q. 4 Reliability in Design
(a) What is the purpose of a FMEA and explain how it is performed, detailing what
information is analysed and the significance of RPN? How does FMEA differ from FTA?
(9 marks)
(b) Describe the Taguchi Robust Concepts (8 marks)
(c) “Human factors must be considered in any product design” Discuss this statement.
(8 marks)
Q. 5 Maintenance Management
(a) Figure 2 beneath illustrates various maintenance strategies. Discuss the relevant
advantages and disadvantages of each strategy. (10 marks)
Figure 2. Maintenance Strategies.
(b) Describe the Overall Equipment Effectiveness (OEE). (7 marks)
(c) Calculate the OEE for the shift data presented beneath in table 2. Comment on the calculated value. (8 marks)
Table 2. Shift Data Item Data Shift Length 8 Hours (480 minutes) Short Breaks (2) 15 minutes each Meal Break (1) 30 minutes Down Time 47 minutes Ideal Rate 60 ppm Pieces Produced 19, Reject Pieces 423
Table 3 – Table of Median Ranks
Table 5 – Optimum Parts Replacement – Values for m
- 1.5 2 2.5 Cf/Cp β
- 2.0 2.229 1.091 0.893 0.810 0.766 0.761 0.775 0.
- 2.2 1.830 0.981 0.816 0.760 0.731 0.733 0.755 0.
- 2.4 1.579 0.899 0.764 0.720 0.702 0.711 0.738 0.
- 2.6 1.401 0.834 0.722 0.688 0.679 0.692 0.725 0.
- 2.8 1.265 0.782 0.687 0.660 0.659 0.675 0.713 0.
- 3.0 1.158 0.738 0.657 0.637 0.642 0.661 0.702 0.
- 3.3 1.033 0.684 0.620 0.607 0.619 0.642 0.687 0.
- 3.6 0.937 0.641 0.589 0.582 0.600 0.627 0.676 0.
- 4.0 0.839 0.594 0.555 0.554 0.579 0.609 0.662 0.
- 4.5 0.746 0.547 0.521 0.526 0.557 0.591 0.648 0.
- 5 0.676 0.511 0.493 0.503 0.538 0.575 0.635 0.
- 6 0.574 0.455 0.450 0.466 0.509 0.550 0.615 0.
- 7 0.503 0.414 0.418 0.438 0.486 0.530 0.600 0.
- 8 0.451 0.382 0.392 0.416 0.468 0.514 0.587 0.
- 9 0.411 0.358 0.372 0.398 0.452 0.500 0.575 0.
- 10 0.378 0.337 0.355 0.382 0.439 0.488 0.566 0.
- 20 0.226 0.230 0.263 0.298 0.364 0.421 0.508 0.
- 30 0.170 0.186 0.222 0.258 0.328 0.387 0.478 0.
