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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2012
Module Title: Maintenance & Reliability
Module Code: MANU
School: Mechanical & Process Engineering
Programme Title: BSc (Honours) in Advanced Manufacturing Technology BSc (Honours) in Process Plant Technology BEng (Honours) in Building Energy Systems
Programme Code: EAMTE_8_Y EPPTE_8_Y EAMTN_8_Y EPPTN_8_Y EBENS_8_Y
External Examiner(s): Mr Kevin McCarthy, Mr Ger Reilly Dr Ben Costelloe, Mr Con Leddy Internal Examiner(s): Mr Dan O’Brien
Instructions: Answer any 3 questions.
Duration: 2 hours
Sitting: Summer 2012
Requirements for this examination: Weibull Hazard Paper, Log-Log Paper, Statistical Tables
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:
(a) MTTF and MTBF are two acronyms used in reliability. Differentiate between both. (4 marks) (b) Explain, using sketches where necessary, the meaning of the following terms used in describing the reliability behaviour of components; and show clearly how they are related to each other; (i) lifetime probability density function; (ii) cumulative distribution function; (iii) reliability function; (iv) hazard function. (8 marks)
(c) A population of components has a reliability function,
1 0.008t
R t^1
Derive h(t) and calculate the failure rate at 500hrs. (8 marks)
(d) Describe with the aid of suitable sketches both active and standby parallel systems. (5 marks)
(e) Three components with Weibull time to fail distributions are placed in parallel. The Weibull distribution parameters are: Table 1. Component Weibull Parameters. Component Shape Parameter Scale Parameter A 4 120hrs B 2 80hrs C 3.5 100hrs
What is the system reliability at time = 200hrs? Given (Weibull pdf):
(8 marks)
e ,for t δ
t δ
f(t)
β θ
β 1 tδ
^
^
Q. 3 Reliability in Design/Human Factors in Reliability
(a) In contrast to FMEA, that predicts failure from part failure, FTA is used to identify parts responsible for product failure as shown in figure 1 beneath. Briefly describe both methods.
Figure 1. FTA and FMEA (8 marks) (b) For the pumping system shown in figure 2 beneath, sketch the Fault Tree and calculate the probability of total loss of output ( TOP event ) given that the probability of occurrence of each PRIME event over some period is as follows:
Table 4. Probability of Occurrence Probability of filter blockage 0. Probability of pipe work failure 0. Probability of electrical supply failure 0. Probability of single pump failure 0.
Figure 2. Pumping System (12 marks) (c) Human factors engineering should be included in every design that requires human interaction, to achieve the greatest potential for reliability. Discuss this statement. (8 marks)
(d) Describe the TESEO method for quantifying human error listing typical applications and limitations. (5 marks)
Q. 4 Maintenance Management / Inventory Management
(a) Differentiate between TPM and RCM. (8 marks)
(b) Discuss the role of vibration signatures in Vibration Monitoring. (6 marks)
(c) Describe Lean Maintenance. (8 marks)
(d) Spare parts management is divided into slow moving spares and fast moving spares. Differentiate between both policies. (4 marks)
(e) Estimate the optimum stockholding for an electric motor, given the following information:
- Estimated cost of holding the motor, CH = €200 per annum
- Estimated cost of not being able to replace from stock in the event of an unexpected failure, CS = €2,000.
- Average lead time for reordering, L = 12 months
- Motor failures occur randomly with an average incidence, D = 0.20 failures per annum. (7 marks)
_Student Name: ________________ Student No: _________________
Figure 4 – Log – Log Paper
_Student Name: ________________ Student No: _________________
Figure 5 – Slow moving spares decision chart.
