Questions
5 questions per paper
Difficulty
Medium
Importance
High yield for HPCL/NTPC/ONGC
Overview
Industrial Engineering is a high-yield area in PSU exams that focuses on optimizing production systems, resource allocation, and quality management. Mastering this topic allows candidates to secure easy marks through numerical-heavy concepts like EOQ and critical path analysis, which frequently appear across all major mechanical engineering papers.
Work Study & Method Study
Work study involves the systematic examination of tasks to improve efficiency by identifying unnecessary movements or delays. It is divided into method study, which focuses on process optimization, and work measurement, which establishes standard times for operations.
- Therbligs: The 17 fundamental motions identified by Frank and Lillian Gilbreth
- SIMO Chart: Simultaneous Motion Cycle chart for micro-motion study
- Performance Rating: Assessing speed relative to a standard operator
- Standard Time = Normal Time + Allowances
- Allowances include relaxation, contingency, and process delays
Inventory Control (EOQ & ABC)
Inventory control focuses on minimizing the total cost of holding and ordering stock items. EOQ models determine the optimal order size, while ABC analysis classifies items based on consumption value to prioritize management attention.
- Economic Order Quantity (EOQ) = sqrt(2 * Demand * Ordering Cost / Holding Cost)
- ABC Analysis: A-items (high value, low quantity), C-items (low value, high quantity)
- Total Inventory Cost = Material Cost + Ordering Cost + Holding Cost
- Reorder Point = Lead Time Demand + Safety Stock
- EOQ is the point where Ordering Cost equals Holding Cost
PERT & CPM
These are project scheduling tools used to analyze network diagrams and optimize project completion time. PERT is probabilistic and used for uncertain projects, while CPM is deterministic and focuses on cost-time trade-offs.
- Expected Time (Te) = (to + 4tm + tp) / 6
- Variance (sigma squared) = ((tp - to) / 6)^2
- Slack = Latest Start - Earliest Start (defined for nodes)
- Float = Latest Finish - Earliest Finish (defined for activities)
- Critical Path: The longest path through the network with zero slack
Quality Control & Control Charts
Statistical Quality Control (SQC) uses control charts to monitor process stability by distinguishing between chance and assignable causes of variation. These charts provide visual limits for maintaining process consistency.
- X-bar chart: Tracks process mean for variable data
- R-chart: Tracks process dispersion or range
- Control Limits: UCL = mu + 3*sigma and LCL = mu - 3*sigma
- C-chart: Used for total number of defects per unit
- p-chart: Used for fraction defective in attribute sampling
Formula Sheet
EOQ = sqrt(2DS/H)
Te = (to + 4tm + tp) / 6
Standard Time = Normal Time * (1 + Allowance Factor)
UCL/LCL = Mean +/- 3 * Standard Deviation
Exam Tip
Always verify units when calculating EOQ, as exam questions often provide annual demand but monthly holding costs, requiring you to standardize timeframes first.
Common Mistakes
- Confusing the denominator in the PERT Expected Time formula (using 3 instead of 6).
- Forgetting to include setup cost in the numerator of the EOQ formula.
- Swapping the definitions of Slack (node-based) and Float (activity-based) in network analysis.
More Revision Notes
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