Quality & Reliability Engineering (QRE) SPPU Endsem Question Paper Nov 2025

Questions

1. Q1

   1. a)

      Explain failure density and failure rate. Describe the main features of the ‘bathtub’ failure rate curve, explaining why each of the three regions has its characteristic shape.

      [8]
   2. b)

      Explain the following Terms (Any 3): i) Safety and Reliability ii) Importance and Reliability iii) Areas of Reliability iv) Uncertainty Analysis in Reliability

      [9]
   OR

2. Q2

   1. a)

      Explain the following probability distributions (Any 2): i) Poisson’s distribution ii) Exponential distribution iii) Log-normal distribution

      [8]
   2. b)

      In an engine manufacturing plant, 70% of the crankshaft is ground by machinist ‘R’ and 30% by machinist ‘S’. It is known from past experience that the crankshaft ground by machinists‘R’ and ‘S’ contain 2 and 3 defective units respectively. If a randomly selected crankshaft is found to be defective, find the probability that it was ground by the machinist ‘R’.

      [5]
   3. c)

      A system has a constant failure rate of 10 –3 /hr. What is the probability that the system will fail before t = 1000 hrs? Determine the probability that it works at least 1000 hr. 2

      [4]

3. Q3

   1. a)

      Write a short note on (Any 2): i) Tie Set and Cut Set Methods of Reliability Evaluation ii) Cold, Hot, and Standby Redundancy Techniques iii) Reliability Evaluation by Conditional Probability Method

      [10]
   2. b)

      This part has equations that don’t show as text. Open the PDF to read it.

      [8]
   OR

4. Q4

   1. a)

      Calculate the reliability for the system shown in the following Fig. 1. The number in each block shows the reliability of the individual component.

      [10]
   2. b)

      This part has equations that don’t show as text. Open the PDF to read it.

      [8]

5. Q5

   1. a)

      What is FMECA? Give the procedure of FMECA. State the importance of RPN in FMECA, with example.

      Also asked:May 2025 ·Nov 2023 ·May 2023

      [9]
   2. b)

      A room with two light bulbs is operated by a single switch. By assuming the ‘No light in the room’ as the top undesirable event. Construct the fault tree for the system shown in Fig 2.

      [8]
   OR

6. Q6

   1. a)

      Write Short notes on: i) Fault Tree Analysis ii) Ishikawa for failure representation (Cause Effect Diagram) iii) Symbols used in FTA

      Also asked:Nov 2023 ·May 2023

      [9]
   2. b)

      A SPM (Special purpose machine) requires a continuous DC supply during operation. A required DC supply is made available through AC to DC converters. Two converters are used in order to ensure uninterrupted DC supply. Converters receive power supply from sub-station which is directly connected to the main supply line. Construct the fault tree for the system shown in Fig 3. 4

      [8]

7. Q7

   1. a)

      i) Explain factors affecting on Maintainability. ii) From the following data collected at a plant: Mean time before failure: 35 Hrs. Mean time to repair: 10 Hrs. Administrative and logistic time: 50% of MTTR Calculate operational availability and inherent availability of the plant.

      Also asked:Nov 2023 ·May 2023

      [10]
   2. b)

      Explain Availability and Maintainability. Show that mean time to repair (MTTR) is the reciprocal of repair rate, from the basic maintainability equation.

      [8]
   OR

8. Q8

   1. a)

      This part has equations that don’t show as text. Open the PDF to read it.

      [10]
   2. b)

      Classify the different tests carried out for Reliability testing and explain in brief (Any 2): i) Accelerated Life Testing (ALT) ii) Highly Accelerated Life Testing (HALT) iii) Highly Accelerated Stress Screening (HASS) 

      [8]