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2003 Course Reliability Engineering

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Total No. of Questions : 11] P1361 [Total No. of Pages : 5 [3864]-175 B.E. (Production) (Common to S/W) RELIABILITY ENGINEERING (2003 Course) (411085) Time : 3 Hours] [Max. Marks : 100 Instructions to the candidates: 1) Answer three questions from section - I. and three questions from section - II. 2) Answers to the two sections should be written in separate books. 3) Neat diagrams must be drawn wherever necessary. 4) Figures to the right indicate full marks. SECTION - I Q1) a) b) Derive an expression MTTF = 1 nk k t N [6] In a survival test conducted on 160 cardboard boxes for their strength under impact loading, the following results were obtained: Number of impacts 20 30 34 36 39 42 45 47 50 Number of boxes failed 17 20 25 24 25 23 13 8 5 For this case, how will you define failure density, failure rate? c) [6] Explain with neat sketch early failure, random failure & wear out failure of Bath tub curve. [4] OR Q2) a) The results of tests conducted under severe adverse conditions on 250 safety valves are tabulated as given below. Calculate failure density (fd) and hazard rate Z(t) when the time interval is four hours instead of one hour. Also calculate number of survivors. [8] Time 00 0-4 4-8 8-12 12-16 16-20 00 135 35 32 22 15 20-24 interval No. of 11 failures P.T.O. b) In the life testing of 200 specimens of a particular device, the number of failures during each time interval of 20 hrs. is shown in table. Estimate MTTF for these specimens. [4] Time Interval {Hours} Number of failures during the interval T<=1000 00 1000<=T<=1020 30 1020<=T<=1040 40 1040<=T<=1060 35 1060<=T<=1080 40 1080<=T<=1100 20 1100<=T<=1120 25 1120<=T<=1140 05 1140<=T<=1160 05 c) Explain with neat sketch meaning of different types of Gates used in the fault tree analysis. [4] Q3) a) Explain the concept of Techno-physico Constraints with a conceptual system. [6] b) Construct a fault tree from Fig.1 such that the top event is a system failure and component failures are basic events. If Pr {A} = Pr {B} = 0.9, Pr {C} = Pr{D} = 0.8 and Pr {E} = Pr{F} = 0.75, compute the probability of the top event. [10] [3864]-175 2 OR Q4) a) Construct a reliability block diagram for given fault tree. Fig. 2 [8] Top Event b) Q5) a) Differentiate between:Design FMEA and Process FMEA. Explain methodology of system analysis. [8] Explain with neat sketch [10] i) ii) b) Series Configuration. General Series-Parallel configuration. Find the system reliability of the configuration in Fig. 3 OR [3864]-175 3 [8] Q6) a) Find the reliability of the configurations shown below in Fig.4 [8] Fig. - 4 b) Explain with neat sketch i) Parallel Configuration. ii) General Parallel - Series configuration. [10] SECTION - II Q7) a) b) Define Terotechnology and explain various elements of LCC. [8] A company is planning to acquire a truck. Two makes of trucks are available in the market. The cost of garaging and the driver s wages are same for both. The other data on cost are provided in the table. Parameters Truck A Truck B Capital cost Rs. 5 Lakhs Rs. 3 Lakhs Annual Road Tax & Rs. 8,000 Rs. 7,000 Operating Cost a) fuel consumption b) oil consumption c) fuel cost d) oil cost 20km/Lit. 2 lit/1000km Rs.3/lit. 25/lit. 20km/ Lit. 2 lit/1000km Rs. 3/lit. 21/lit. Maintenance Cost a) service interval b) cost of service c) random breakdown d) cost of breakdown Every 7,000 km. Rs.3,000 Every30,000 km. Rs.9,000. Every 4,000 km. Rs.5,000 Every10,000 km. Rs.6,000. Expected life 10 yrs. 10 yrs. Insurance Calculate annual maintenance cost for a period of 30,000 km & find out which truck is advantageous? [8] [3864]-175 4 Q8) a) b) OR Explain mean and median ranking method. [8] The following data refer to Mean time to failure of a equipment used in electric power house installation: [8] No. of failure 1 2 3 4 5 MTTF/MTBF 31.3 45.9 78.3 22.1 2.3 (Hrs) 6 4.8 7 8 9 8.1 11.3 17.3 Plot the reliability against time using the method median statistics. How will values changes with mean statistics? Q9) a) b) Explain : i) Inherent availability. ii) Achieved availability. iii) Operational availability. If two components having failure rates 1, 2 respectively are connected in parallel show that the Reliability of this parallel configuration at time t is given as. Rp(t) = e 1t + e 2t e Q10)a) b) [6] [10] ( 1+ 2)t OR Derive and expression for techno-economic life of equipment given maintenance function (atn), operating cost per year (v) and first cost (C).[6] The following data have been collected at the plant: [6] Mean time before failure = 30hrs. Mean time to repair = 15hrs. Administrative logistic time is 30% of Mean Down Time(MDT). Calculate the operational availability and inherent availability of the plant. c) Explain the term availability and maintainability of system. Q11)Write short note on (Any 3) a) k out of m systems. b) Types of maintenance system. c) Risk priority number in FMEA. d) Tie-set & cut set . e) Redundancy. 88888 [3864]-175 5 [4] [18]

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